16 Марта 2017
Короткий путь в науку
15 Февраля 2017
Опубликован Каталитический бюллетень
The scientific cooperation of the Boreskov Institute of Catalysis with the catalytic communities from various countries is effected in accordance with various forms of cooperation: conducting joint seminars on catalysis, exchanging the information and appropriate materials, exchanging research fellows, visiting scientific centers, and participating in congresses and symposia on theoretical and applied catalysis.
According to research programs, projects and grants, the fundamentals of catalysis are studied jointly with researchers from various universities, institutions, research laboratories and companies. BIC collaborates fruitfully on a commercial basis with the leading companies from more than 20 countries, sells licenses, know-how and performs research projects according to client requests.
Academician Valentin N. Parmon is the Russian representative in the European Federation of Catalytic Societies (EFCATS), Member of the International Association of the Catalysis Societies (IACS).
According to the agreement between RAS and CNRS BIC collaborates with the Institute de Recherches sur la Catalyse et l’Environnement de Lyon (Research Institute on Catalysis and Environment), Villeurbanne, in the frame of the Russian-French European associated Laboratory on Catalysis headed by Prof. V. Parmon and Dr. M. Lacroix. The Laboratory was established by an agreement signed December 6, 2004 in Moscow by RAS and CNRS. Four areas of research were identified:
In the frame of RAS-DST Long Term Programme of cooperation in science and technology BIC collaborates with National Chemical Laboratory, Pune. Coordinators on the Program “Catalysis” are Prof. V. Parmon and Prof. S. Sivaram.
The cooperation in the frame of the agreement between RAS and German Scientific Research Society (GSRS) with Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, on the Project “Development of in situ Methods for Study of Solid Surfaces”. Coordinators: Prof. V. Bukhtiyarov (BIC) and Prof. R. Sсhlögl (Fritz-Haber-Institut der MPG)
The cooperation in the frame of Associated Research Laboratory which was established by an agreement signed December 4, 2004 by the Boreskov Institute of Catalysis and Heilongjiang University, Harbin. Chief Executive officers of Laboratory are: Prof. V. Bukhtiyarov, Prof. G. Echevsky (BIC) and Prof. Wu Wei (Heilongjiang University) on the Project “Synthesis and Modification of ZSM-12 Zeolites. Zeolite ZSM-12 in Reaction of Naphthalene Alkylation with Methanol”.
The cooperation in the frame of the bilateral agreement with the Purdue University, Indiana.
EUROPEAN COMMUNITY SIXTH FRAMEWORK PROGRAM
I. Co-Processing of Upgraded Bio-Liquids in Standard Refinery Units
Coordinator: Dr. Y. Solantausta, VTT Processes, Espoo, Finland
Rijksuniversiteit Groningen, The Netherlands; Boreskov Institute of Catalysis, Novosibirsk, Russia (Prof. V. Kirillov); Uhde Hochdrucktechnik GmbH, Germany; BTG Biomass Technology Group BV, The Netherlands; University of Twente, The Netherlands; STFI-PACKFORSK AG, Sweden; Institute of Wood Chemistry, Hamburg, Germany; Slovenian Institute of Chemistry, Slovenia; Arkema SA, France; Helsinki University of Technology, Finland; ALMA Consulting Group SAS, France; INEOS Phenol, Germany; Metabolic Explorer, France; Shell Global Solutions International, The Netherlands; Pacific Northwest National Laboratory (PNNL), USA; Johnson Matthey, UK.
EUROPEAN COMMUNITY SEVENTH FRAMEWORK PROGRAM
I. Reforming of Crude Glycerin in Supercritical Water to Produce Methanol for Re-Use in Biodiesel Plants
Coordinator: J. Vos, BTG BiomassTechnology Group BV, The Netherlands
Acciona Servicios Urbanos, Spain; Boreskov Institute of Catalysis, Novosibirsk, Russia (Prof. V. Kirillov); Rijksuniversiteit Groningen, The Netherlands; University of Maribor, Slovenia; UHDE High Pressure Technologies GmbH, Germany; SPARQLE International BV, The Netherlands.
II. Engine and Turbine Combustion of Bioliquids for Combined Heat and Power Production
Coordinator: J. Vos, BTG BiomassTechnology Group BV, The Netherlands
AMO ZIL, Moscow, Russia; Aston University, Birmingham, UK; Boreskov Institute of Catalysis, Novosibirsk, Russia (Prof. V. Kirillov); BTG Biomass Technology Group BV, The Netherlands; Central Scientific Automobile and Automotive Engines Institute, NAMI, Moscow, Russia; Encotech BV, The Netherlands; University of Florence, Florence, Italy.
III. Oxidative Coupling of Methane Followed by Oligomerization to Liquids
Coordinator: G. Marin, Ghent University, Belgium
Bayer Technology Service, Germany; Institute de Recherches sur la Catalyse et l’Environnement de Lyon, Villeurbanne, France; Ruhr-Universität Bochum, TECHEM, Bochum, Germany; Instituto de Technologia Quimica, Spain; Johnson Matthey, UK; SINTEF, Trondheim, Norway; Linde Engineering, Germany; Cepsa R&D Center, Spain; Haldor Topsoe, Denmark; Universitetet i Oslo, Oslo, Norway; University of Cambridge, UK; ALMA Consulting Group, France; Boreskov Institute of Catalysis, Novosibirsk, Russia (V. Sadykov); INEOS, Belgium; Institut fur Mikrotechnik Mainz Gmbh, Germany; Eni SpA, Italy.
IV. Design and Manufacturing of Catalytic Membrane Reactors by Developing New NanoArchitectured Catalytic and selective Membrane Materials (DEMCAMER)
Coordinators: Fernando Espiga Guy Marin and/or Inaki San Sebastian, Fundacion Tecnalia Research & Innovation, Spain
Vlaamse Instelling voor Technologisch Onderzoek N.V., Belgium; Universita della Calabria, Italy; Technische Untversiteit Eindhoven, Netherlands; Agencia Estatal Consejo Superior de Investigaciones Cientificas, Spain; Fraunhofer-Gesellschaft zur Foerderung der Angewandten Forschung e.V., Germany; Boreskov Institute of Catalysis, Russia (Dr. I.Z. Ismagilov); Institut National de l'Environnement et des Risques Ineris, France; Rauschert Kloster Veilsdorf GMBH, Germany; Ceramic Powder Technology AS, Norway; Hybrid Catalysis BV, The Netherlands; HyGear B.V., The Netherlands; Abengoa Bioenergia Nuevas Tecnologias SA, Spain; Guascor Ingenieria S.A., Spain represented; Quantis Sari, Switzerland; Höganäs AB, Sweden; Total Petrochemicals Research Feluy, Belgium; Total Petrochemicals France SA, France.
The advertising and information activities are universal marketing tools for establishing professional contacts. Again, this is a necessary part of the market examination to be settled in the world. Each year, achievements of the Boreskov Institute of Catalysis are demonstrated at the very prestigious exhibitions in Russia and abroad. The goal is to strengthen collaboration with the present partners and to attract attention of potential customers.
In 2011, the most important BIC’s achievements in the area of applied catalysis were presented at the Exhibitions:
Solution of many specific problems requires joint efforts in order to promote its fastest accomplishing. International congresses, symposia, conferences, and seminars are the most productive to familiarize scientists with innovations outside their own research and to disseminate the information about the results achieved to a wider audience. One of the directions of the scientific-organizational work carried out in the Institute is aimed on conducting conferences and seminars with the participation not only of Russian scientists and researchers from fSU, but foreign participants as well.
MODELING OF THE MECHANISM OF ONE-ELECTRON TRANSFER FROM THE PERYLENE MOLECULE TO THE OXYGEN MOLECULE 3O2 IN THE HF MEDIUM
I.V. Kuz’min*, V.N. Solkan*, G.M. Zhidomirov, V.B. Kazanskii* (*Zelinsky Institute of Organic Chemistry, Moscow, Russia)
Kinet. Catal., 52(2) (2011) pp. 192-196.
The thermodynamic parameters of the formation of the perylene radical cation in anhydrous hydrogen fluoride containing dissolved dioxygen were calculated by the ab initio method MP2. The protonated product of HF autoprotolysis was modeled as the H(FH)3+ cluster. The 3O2 molecule was found to bind to the linear H(FH)3+ cluster via a hydrogen bond. As the charge and multiplicity of the system change upon the capture of an electron, the oxygen-hydrogen fluoride cluster complex undergoes rearrangement to yield the hydroperoxyl radical OOH incorporated in a cycle formed by HF molecules. The free energy of electron transfer from the perylene molecule to the 3O2 molecule in the HF medium is about -38 kcal/mol.
A QUANTUM-CHEMICAL MODEL OF THE INHIBITION MECHANISM
G.A. Yuldasheva*, G.M. Zhidomirov, A.I. Ilin*
(*Anti-Infective Drug Research Center, Almaty, Kazakhstan)
Nat. Sci., 3(7) (2011) pp. 573-579.
The interaction of molecular iodine with virus DNA nucleotide is studied by ab initio RHF/3-21G** method. Formation of the nucleoprotein complex of the HIV DNA, molecular iodine and the HIV-1 integrase co-factor is considered to cause the inhibition action of the integrase enzyme. Experimental data on the anti-HIV effect of the molecular iodine complex compounds and the results of calculations suggest that molecular iodine contained in iodine polymer complexes may be considered as a compound inhibiting the catalytic center of the integrase enzyme. Unlike the known integrase inhibitors, molecular iodine also changes the virus DNA structure and produces the N-I bond in the purine bases of adenosine and guanosine nucleotides.
OXIDE CLUSTERS AS SOURCE OF THE THIRD OXYGEN ATOM FOR THE FORMATION OF CARBONATES IN ALKALINE EARTH DEHYDRATED ZEOLITES
A.V. Larin*, A.A. Rybakov*, G.M. Zhidomirov, A. Mace**, A. Laaksonen**, D.P. Vercauteren***
(*Moscow Lomonosov State University, Moscow, Russia; **University of Stockholm, Stockholm, Sweden; ***University of Namur, Namur, Belgium)
J. Catal., 281(2) (2011) pp. 212-221.
It is shown that carbonates can be formed with almost no energetic barrier from CO2 and metal-oxide binuclear MOxM species (M = Mg, Ca, Sr, Ba, with X = 1–4, depending on the cation) in alkaline earth zeolites, mordenite (MOR) and phillipsite (PHI), on the basis of quantum mechanical density functional theory (DFT) calculations at both isolated cluster and 3D periodic levels. The participation of MOxM species (X = 1 and 3) explains the source of the third O atom in CO3 species in dehydrated zeolites, on the basis of a good agreement between the calculated and experimental positions of the asymmetric and symmetric CO3 vibration bands, of the ratio of their intensities, and of the weak dependence versus the cation and framework type. The reaction of formation of dimethylcarbonate from CaCO3Ca in the 8-membered (8R) ring of MOR and methanol has also been considered, suggesting the carbonate activity as the source of CO2 at elevated temperatures.
DFT INVESTIGATION OF CO OXIDATION OVER Mg EXCHANGED PERIODIC ZEOLITE MODELS
A.A. Rybakov*, A.V. Larin*, G.M. Zhidomirov, D.N. Trubnikov*, D.P. Vercauteren** (*Moscow Lomonosov State University, Moscow, Russia; **University of Namur, Namur, Belgium)
Comput. Theor. Chem., 964(1-3) (2011) pp. 108-115.
A new CO oxidation mechanism occurring at (MgO2Mg)2+ oxide clusters in different zeolites is modeled at both the periodic DFT (PDFT) level for Mg-phillipsite and with the cluster approach for zeolite Y and mordenite. Using PDFT, the authors obtained a value of reaction activation energy (15.3 kcal/mol) that is lower than the one obtained using the isolated cluster approach (35 kcal/mol).
The main reason of the lower barrier is the strong CO chemisorption, which was not obtained with the cluster approach. The lower oxidation activity of the Mg zeolite forms is due to the smaller number of active singlet MgOxMg species compared to those in the other alkaline earth zeolites.
Cu(II)-Alkyl CHLOROCOMPLEXES: STABLE COMPOUNDS OR TRANSIENTS? DFT PREDICTION OF THEIR STRUCTURE AND EPR PARAMETERS
E.N. Golubeva*, O.I. Gromov*, G.M. Zhidomirov(*Moscow Lomonosov State University, Moscow, Russia)
J. Phys. Chem. A, 115(28) (2011) pp. 8147-8154.
DFT calculations were used for studying the structure and reactivity of organocuprates(II) usually considered as intermediates with very weak Cu-C bond. It was found that calculated principal g-tensor values of model compounds RCu(II)Cl2- are similar to the experimentally found values for organocopper product of photolysis of quaternary ammonium tetrachlorocuprates. The calculations confirm that the most of organocuprates(II) could be stable at ambient conditions, and short lifetimes of organocuprates(II) in solutions or soft matrices are caused by their high reactivity in various bimolecular processes; the rate of those may be close to the rate of diffusion controlled reactions. The charges, spin densities, and d-orbital populations of the Cu atom in them are typical for bivalent copper complexes. Natural bond orbital analysis of organochlorocuprates(II) confirms the formation of polar σ-bond between copper and carbon atoms.
ROLE OF THE SURFACE HYDROXYL GROUPS OF MODIFIED TITANIUM OXIDE IN CATALYTIC ETHYLENE OXIDE HYDRATION
D.E. Zavelev*, M.V. Tsodikov*,cvG.M. Zhidomirov, R.A. Kozlovskii* (*Topchiev Institute of Petrochemical Synthesis, Moscow, Russia)
Kinet. Catal., 52(5) (2011) pp. 659-671.
A quantum-chemical study of the mechanism of ethylene oxide hydration on titanium oxide (anatase) modified with phosphorus additives was performed. It was demonstrated that the hydroxyl groups of the anatase surface are of importance for the activation interaction of ethylene oxide with the catalyst surface. The activation of the ethylene oxide molecule and proton transfer occurs with the participation of these hydroxyl groups. It was found that the modification of the titanium oxide surface with phosphorus additives plays a crucial role in proton transfer.
EFFECT OF LATTICE STRAIN ON HYDROGEN DIFFUSION IN Pd: A DENSITY FUNCTIONAL THEORY STUDY
H. Gronbeck*, V.P. Zhdanov (*Chalmers University of Technology, Göteborg, Sweden)
Phys. Rev. B: Condens. Matter, 84(5) (2011) 052301 (4 pp.)
The density functional theory (DFT) is used to study the effect of lattice strain on hydrogen diffusion in Pd. The activation energy for this process is found to increase dramatically with increasing compressive lattice strain. In particular, the activation energy is close to double for an isotropic compression of 5% both in the alpha and beta phases. For tensile strain, the activation energy is instead decreased. This finding has important consequences for the interpretation of various kinetic processes occurring with participation of hydrogen and other interstitial atoms in macroscopic solid samples and nanoparticles.
DFT STUDIES OF PALLADIUM MODEL CATALYSTS: STRUCTURE AND SIZE EFFECTS
I.V. Yudanov, A. Genest*, N. Rösch* (*Technische Universität München, Garching, Germany)
J. Clust. Sci., 22(3) (2011) pp. 433-448.
An important task for theory is the multi-scale modeling of catalytic properties of nanocrystallites with sizes ranging from clusters of few metal atoms to particles consisting of 103–104 atoms. To explore catalytic properties of nanosized metal catalysts, the authors developed an approach based on three-dimensional symmetric model clusters of 1–2 nm (~100 metal atoms) with fcc structure, terminated by low-index surfaces. With this modeling technique one is able to describe at an accurate DFT level various catalytic and adsorption properties of metal nanoparticles in quantitative agreement with experimental studies of model catalysts deposited on thin oxide films. Metal nanocrystallites exhibit properties that can significantly vary with their size and shape.
MOLECULAR MECHANISM OF THE FORMIC ACID DECOMPOSITION ON V2O5/TiO2
CATALYSTS: A PERIODIC DFT ANALYSIS
V.I. Avdeev, V.N. Parmon
J. Phys. Chem. C, 115(44) (2011) pp. 21755-21762.
Molecular and dissociative forms of formic acid adsorption on the V2O5/TiO2 model surface, possible intermediates, and transition states along of the dehydrogenation (HCOOH → CO2 + H2) and dehydration (HCOOH → CO + H2O) pathways have been studied by the periodic density functional theory. The CI-NEB analysis of the reaction pathways showed that two types of molecular adsorbed HCOOH species initiate two completely different reaction channels. The first more stable adsorbed form is transformed into the surface formates, which decompose according to the “formate mechanism” to yield products of dehydrogenation, whereas the second weakly adsorbed molecular form decomposes, releasing CO and forming surface hydroxyls. Recombination of two surface hydroxyl groups V–OH to form adsorbed H2O, followed by water desorption, completes the catalytic dehydration cycle without participation of the formate species. Comparison of the reaction pathways demonstrates that both dehydrogenation and dehydration of formic acid may occur over VOx/TiO2 model catalysts with the preferable dehydration pathway.
ADSORPTION ENERGY OF THE As ATOM ON THE Pd(111) SURFACE ACCORDING TO THE DENSITY FUNCTIONAL THEORY DATA
S.E. Malykhin, M.Yu. Burylin*, S.Yu. Burylin*, I.L. Zilberberg (*Kuban State University, Krasnodar, Russia)
J. Struct. Chem., 52(6) (2011) pp. 1098-1101.
Density functional theory in the plane wave basis set is used to study As adsorption on the Pd(111) surface in order to determine the action of a palladium chemical modifier used in electrothermal atomic absorption spectrometry (ETAAS). The calculated heat of desorption of the arsenic atom is 435 kJ/mole, which corresponds to the activation energy of arsenic atomization of 439 kJ/mole (in the range of high temperatures T > 1828 K), obtained by ETAAS. Based on the calculated data, the action of the palladium modifier for the determination of As is assumed to be controlled by the process of chemisorption.
AN ab initio STUDY OF ELECTROCHEMICAL vs. ELECTROMECHANICAL PROPERTIES: THE CASE OF CO ADSORBED ON A Pt(111) SURFACE
M.I. Mamatkulov, J.-S. Filhol* (*Université Montpellier, Montpellier Cedex, France )
Phys. Chem. Chem. Phys., 13(17) (2011) pp. 7675-7684.
The authors have studied electrochemical vibrational and energy properties of CO/Pt(111) in the framework of periodic density functional theory (DFT) calculations. The authors have used a modified version of the previously developed Filhol-Neurock method to correct the unphysical contributions arising from homogeneous background countercharge in the case of thick metallic slabs. The stability of different CO adsorption sites on Pt(111) (Top, Bridge, Hcp, Fcc) has been studied at constant electric field. The energies are dominated by the surface dipole interaction with the external electric field: a strong positive electric field favors the surfaces with the lower dipole moment (that correspond to the ones with the lower coordination). The Stark tuning slope of the CO stretching frequency for a Top site was calculated for different surface coverages in very good agreement with both experimental and other theoretical results. Finally, an analysis of the origin of Stark shifts showing that the total Stark effect can be split into two competing components have been performed. The first one corresponds to the direct effect of charging on the C-O chemical bond: it is referred as an electrochemical effect. The second is the consequence of the surface dipole interaction with the applied electric field that modifies the C-O distance, inducing a change of the C-O force constant because of C-O bond anharmonicity: it is referred as the electromechanical effect. In the CO/Pt(111) case, the dominant contribution is electromechanical. The electrochemical contribution is very small because the electronic system involved in the surface charging is mostly non-bonding as analyzed by looking at the surface Fukui function.
ARE THE COMPLEX DISTRIBUTED GENETIC NETWORKS INHERENTLY OSCILLATORY AND CHAOTIC?
JETP Lett., 93(1) (2011) pp. 41-45.
Complex mRNA-protein networks with distributed regulation of gene transcription are often mimicked by random Boolean networks. According to this mapping, the gene-expression kinetics are expected to depend strongly on the network connectivity, m. Specifically, the kinetics are predicted to be oscillatory or chaotic for m > 2. The authors analyze this problem in more detail by using an accurate model explicitly describing the mRNA-protein interplay with randomly organized transcriptional regulation. Contrary to the expectations, mean-field calculations and Monte Carlo simulations performed for m = 1, 2 and 4 show that oscillations and chaos are lacking irrespective of m.
KINETIC MODELS OF GENE EXPRESSION INCLUDING NON-CODING RNAs
Phys. Rep.-Rev. Sec. Phys. Lett., 500(1) (2011) pp. 1-42.
n cells, genes are transcribed into mRNAs, and the latter are translated into proteins. Due to the feedbacks between these processes, the kinetics of gene expression may be complex even in the simplest genetic networks. The corresponding models have already been reviewed in the literature. A new avenue in this field is related to the recognition that the conventional scenario of gene expression is fully applicable only to prokaryotes whose genomes consist of tightly packed protein-coding sequences. In eukaryotic cells, in contrast, such sequences are relatively rare, and the rest of the genome includes numerous transcript units representing non-coding RNAs (ncRNAs). During the past decade, it has become clear that such RNAs play a crucial role in gene expression and accordingly influence a multitude of cellular processes both in the normal state and during diseases. The numerous biological functions of ncRNAs are based primarily on their abilities to silence genes via pairing with a target mRNA and subsequently preventing its translation or facilitating degradation of the mRNA-ncRNA complex. Many other abilities of ncRNAs have been discovered as well. The review is focused on the available kinetic models describing the mRNA, ncRNA and protein interplay. In particular, the authors systematically present the simplest models without kinetic feedbacks, models containing feedbacks and predicting bistability and oscillations in simple genetic networks, and models describing the effect of ncRNAs on complex genetic networks. Mathematically, the presentation is based primarily on temporal mean-field kinetic equations. The stochastic and spatio-temporal effects are also briefly discussed.
PERIODIC PERTURBATION OF THE BISTABLE KINETICS OF GENE EXPRESSION
Physica A, 390(1) (2011) pp. 57-64.
Kinetics of gene expression may be bistable or oscillatory due to the feedbacks between the RNA and protein synthesis. In complex genetic networks, kinetic oscillations may influence bistability. Following this line, the authors have performed a mean-field analysis and Monte Carlo simulations of periodic perturbation of the bistable kinetics of expression of two genes with mutual suppression of the mRNA production due to negative regulation of the gene transcription by protein. The perturbation is realized via modulation of the rate of the mRNA formation. In the mean-field kinetics, the mRNA and protein concentrations repeat themselves during each period. In the stochastic kinetics, this is also the case, provided that the modulation amplitude is small. If the modulation is appreciable, the latter kinetics exhibit new features. Specifically, the model predicts stochastic intermittence of the states of the genes. If the modulation amplitude is close to maximum, the change of the gene states during subsequent perturbation periods occurs fully at random. Taking into account that the model the authors use is generic, the results obtained are expected to be of interest far beyond the biophysics and biochemistry of gene expression.
GROWTH AND GLOBAL GENE EXPRESSION OF EUCARYOTIC CELLS
Biophys. Rev. Lett., 6(1-2) (2011) pp. 1-12.
The authors present a kinetic model describing the growth of eukaryotic cells or, more specifically, the dependence of the cell volume on time in terms of the global interplay of the mRNA and protein synthesis and degradation and lipid synthesis. Addressing two long-standing questions in this interdisciplinary field, the authors explain why the average protein concentration in growing cells is nearly constant and the growth can accurately be fitted by using a bilinear or exponential function.
NON-CODING RNAs AND COMPLEX DISTRIBUTED GENETIC NETWORKS
Central Eur. J. Phys., 9(4) (2011) pp. 909-918.
In eukaryotic cells, the mRNA-protein interplay can be dramatically influenced by non-coding RNAs (ncRNAs). Although this new paradigm is now widely accepted, an understanding of the effect of ncRNAs on complex genetic networks is lacking. To clarify what may happen in this case, a mean-field kinetic model was proposed describing the influence of ncRNA on a complex genetic network with a distributed architecture including mutual protein-mediated regulation of many genes transcribed into mRNAs. ncRNA is considered to associate with mRNAs and inhibit their translation and/or facilitate degradation. Results are indicative of the richness of the kinetics under consideration. The main complex features are found to be bistability and oscillations. One could expect to find kinetic chaos as well. The latter feature has however not been observed in calculations. In addition, the authors illustrate the difference in the regulation of distributed networks by mRNA and ncRNA.
KINETIC MODELS OF THE INTERFERENCE OF GENE TRANSCRIPTION TO ncRNA AND mRNA
Chaos, 21(2) (2011) 023135 (7 pp.).
The experiments indicate that the transcription of genes into ncRNA can positively or negatively interfere with transcription into mRNA. Two kinetic models are proposed describing this effect. The first model is focused on the ncRNA-induced chromatin modification facilitating the transcription of the downstream gene into mRNA. The second model includes the competition between the transcription into ncRNA and the binding of activator to a regulatory site of the downstream gene transcribed into mRNA. The analysis based on the mean-field kinetic equations and Monte Carlo simulations shows the likely dependences of the transcription rate on RNA polymerase concentration in situations with different rate-limiting steps. The models can also be used to scrutinize the dependence of the transcription rate on other kinetic parameters. Kinetic Monte Carlo simulations show that the first model predicts stochastic bursts in the mRNA formation provided that the transcription into ncRNA is slow, while the second model predicts in addition anti-phase stochastic bursts in the mRNA and ncRNA formation provided that that the protein attachment to and detachment from a regulatory site is slow.
INTERPLAY OF VIRAL miRNAs AND HOST mRNAs AND PROTEINS
Central Eur. J. Phys., 9(5) (2011) pp. 1366-1371.
Recent experiments indicate that several viruses may encode microRNAs (miRNAs) in cells. Such RNAs may interfere with the host mRNAs and proteins. A kinetic analysis of this interplay s presented. The viral miRNA is considered to be able to associate with the host mRNA with subsequent degradation. This process may result in a decline of the mRNA population and also in a decline of the population of the protein encoded by this mRNA. With these ingredients, it was first shown the types of the corresponding steady-state kinetics in the cases of positive and negative regulation of the miRNA synthesis by the protein. In addition, the authors scrutinize the situation when the protein regulates the virion replication or, in other words, provides a feedback for the replication. For the negative feedback, the replication rate is found to increase with increasing the intracellular virion population. For the positive feedback, the replication rate first increases and then drops. These features may determine the stability of steady states.
FROM STICKING TO SLIPPING CONDITIONS IN QCM-D
V.P. Zhdanov, B. Kasemo* (*Chalmers University of Technology, Göteborg, Sweden)
Chem. Phys. Lett., 513(1-3) (2011) pp. 124-126.
Supported lipid bilayers are often studied by using quartz crystal microbalance with dissipation monitoring (QCM-D). The interpretation of the QCM-D data usually implies the no-slip boundary condition at the substrate (QCM) surface. Under certain circumstances, the oscillations of the QCM crystal may however result in the transition to slipping conditions. Employing the Frenkel-Kontorova model, the authors show that during this transition the amplitude of the bilayer vibrations drops in a stepwise fashion, i.e., the process can be classified as a first-order kinetic phase transition. The model allows also to scrutinize the corresponding changes in the force between the bilayer and support and dissipation of energy.
A KINETIC MODEL OF STANDARD SELECTIVE CATALYTIC REDUCTION OF NO BY NH3 ON SINGLE SITES
React. Kinet. Mech. Catal., 103(1) (2011) pp. 11-18.
Reduction of NO by NH3 in the presence of O2 may occur on single Fe or Cu atoms or dimers incorporated into the inner walls of a zeolite. Although this process is of considerable intrinsic interest as an example of complex reactions running on single sites and is also important from the perspective of environmental chemistry, its mechanism is still open for debate. One of the likely schemes of the process implies the formation of N2 and H2O via the reaction of gas-phase NO and adsorbed NH3. The author presents a detailed analysis of the steady-state kinetics corresponding to this scheme. The model employed includes eleven elementary steps. The results obtained allow one to interpret the apparent reaction orders observed experimentally.
A KINETIC MODEL OF STANDARD SELECTIVE CATALYTIC REDUCTION OF NO BY NH3 ON TWO SITES
React. Kinet. Mech. Catal., 104(2) (2011) pp. 267-272.
Reduction of NO by NH3 in the presence of O2 may occur on single Fe or Cu atoms or dimers incorporated into the inner walls of zeolite. One of the likely schemes of this reaction implies the formation of N2 and H2O through the reaction of gas-phase NO and adsorbed NH3. The steady-state kinetics corresponding to this scheme was recently analyzed by the author assuming that the reaction runs on single metal atoms. In this work, the author presents a model including two metal atoms. Under the practically important conditions, the kinetics predicted by the one- and two-site models are demonstrated to be similar. In particular, both models allow one to interpret the apparent reaction orders observed experimentally.
KINETICS OF CELL-TO-CELL SPREAD OF VIRUSES
JETP Lett., 93(9) (2011) pp. 551-554.
Recent experiments indicate that many viruses can move between cells directly via the cell–cell contacts without diffusing through the extracellular environment. The first generic kinetic model is presented describing intracellular viral kinetics in combination with this mode of spread of virions. Monte Carlo simulations show the specifics of the propagation of the infection front in this case.
INTERACTION OF SINGLE VIRUS-LIKE PARTICLES WITH VESICLES CONTAINING GLYCOSPHINGOLIPIDS
M. Bally*, A. Gunnarsson*, L. Svensson**, G. Larson***, V.P. Zhdanov, F. Hook* (*Chalmers University of Technology, Göteborg, Sweden; **University of Linköping, Linköping, Sweden; ***University of Gothenburg, Göteborg, Sweden)
Phys. Rev. Lett., 107(18) (2011) 188103 (5 pp.).
Glycosphingolipids are involved in the first steps of virus-cell interaction, where they mediate specific recognition of the host cell membrane. The authors have employed total-internal-reflection fluorescence microscopy to explore the interaction kinetics between individual unlabeled noroviruslike particles, which are attached to a glycosphingolipid-containing lipid bilayer, and fluorescent vesicles containing different types and concentrations of glycosphingolipids. Under association equilibrium, the vesicle-binding rate is found to be kinetically limited, yielding information on the corresponding activation energy. The dissociation kinetics are logarithmic over a wide range of time. The latter is explained by the vesicle-size-related distribution of the dissociation activation energy. The biological, pharmaceutical, and diagnostic relevance of the study is briefly discussed.
DISSOLUTION AND REDEPOSITION ON Pt NANOPARTICLES UNDER ELECTROCHEMICAL CONDITIONS
V.P. Zhdanov, B. Kasemo* (*Chalmers University of Technology, Göteborg, Sweden)
Chem. Phys. Lett., 509(4-6) (2011) pp. 134-137.
A Schottky-type model describing Pt2+ dissolution and redeposition on Pt nanoparticles in polymer electrolyte fuel cells is presented. The charge transfer is considered to occur near the surface of nanoparticles so that the potential barrier for the reaction is formed by the double-layer potential and the image interaction. With increasing electrode potential, the transfer coefficient for dissolution is found to decrease from 0.6-0.7 down to 0.3-0.4. Its dependence on the effective dielectric constant of the double layer is appreciable while the dependence on the particle size is weak.
POTENTIAL PROFILES NEAR THE SCHOTTKY NANOCONTACTS
V.P. Zhdanov, B. Kasemo* (*Chalmers University of Technology, Göteborg, Sweden)
Physica E, 43(8) (2011) pp. 1486-1489.
The conventional Schottky model describes in the mean-field approximation the electrostatic potential appearing in a doped semiconductor during its flat contact with a metal. More recently, the Schottky model has been used to describe the mean-field potential profile near a metallic nanosphere surrounded by or located on the surface of a semiconductor. The authors present the corresponding results for a metallic nanowire. In these three cases, the shape of the potential profiles and their scalings are very different. In particular, the full width at half maximum of the potential barrier dramatically shrinks if the geometry changes from linear to cylindrical and then to spherical. In addition, the authors scrutinize the effect of the discreteness of the dopant charges on the potential near a metallic nanosphere.
INFLUENCE OF THE MOBILITY OF OXYGEN ON THE REACTIVITY OF La1-xSrxMnO3 PEROVSKITES IN METHANE OXIDATION
D.V. Ivanov, L.G. Pinaeva, E.M. Sadovskaya, L.A. Isupova
Kinet. Catal., 52(3) (2011) pp. 401-408.
Radically different dependences of the activity of La1-xSrxMnO3 (x = 0-0.5) perovskites in methane oxidation on the degree of substitution of strontium for lanthanum are observed for low and high temperatures. Unsubstituted LaMnO3 exhibits the highest activity in the temperature range from 300 to 500°C, while the sample with the maximum degree of substitution (La0.5Sr0.5MnO3) shows the highest activity at higher temperatures of 700–900°C. In the low temperature region, the activity of La1-xSrxMnO3 is determined by the amount of weakly bound (overstoichiometric) oxygen, which is formed in cation-deficient lattices and is characterized by a thermal desorption peak with Tmax = 705°C. At higher temperatures (800–900°C), the strongly bound oxygen of the catalyst lattice is involved in the formation of the reaction products under both unsteady- and steady-state conditions. As a consequence, the catalytic activity in methane oxidation correlates with the apparent rate constant of oxygen diffusion in the oxide bulk.
INSIGHTS INTO THE REACTIVITY OF La1-xSrxMnO3 (x = 0 ÷ 0.7) IN HIGH TEMPERATURE N2O DECOMPOSITION
D.V. Ivanov, L.G. Pinaeva, L.A. Isupova, A.N. Nadeev, I.P. Prosvirin, L.S. Dovlitova
Catal. Lett., 141(2) (2011) pp. 322-331.
In this paper a wide range of La1-xSrxMnO3 (x = 0–0.7) perovskites was synthesized by Pechini route, characterized by XRD (including high temperature measurements), XPS, differential dissolution phase analysis, TPR H2, oxygen exchange and tested in N2O decomposition at 900°C. At low degree of Sr substitution for La (x ≤ 0.3), high catalytic activity was found for perovskites with hexagonal structure (x = 0.1-0.2) and can be related to fast oxygen mobility caused by the lattice disordering during polymorphic phase transition from the hexagonal to cubic structure. For multiphase samples (x > 0.3) increase of activity and oxygen mobility can be attributed to the formation of the layer structured perovskite - LaSrMnO4 on the surface.
MECHANISM OF 1,2-DICHLOROETHANE DEHYDROCHLORINATION ON THE ACID SITES OF OXIDE CATALYSTS AS STUDIED BY IR SPECTROSCOPY
A.S. Shalygin, L.V. Malysheva, E.A. Paukshtis
Kinet. Catal., 52(2) (2011) pp. 305-315.
The adsorption of 1,2-dichloroethane on zeolite HZSM-5 and y-Al2O3 at temperatures from 25 to 400°C was studied by Fourier transform IR spectroscopy. The forms of adsorbed 1,2-dichloroethane and the products of its conversion at the Brønsted and Lewis acid sites of catalysts were identified. The kinetics of 1,2-dichloroethane conversion on the surface of catalysts was studied by in situ Fourier transform IR spectroscopy. It was demonstrated that 1,2-dichloroethane was dehydrochlorinated at the Lewis sites of y-Al2O3 even at 100°C, whereas the reaction came into play at the Brønsted sites of zeolite HZSM-5 only at 200°C. It was found that, at the Lewis acid sites of catalysts, the resulting vinyl chloride underwent oligomerization with the intermediate formation of a dimer (1,3-dichloro-2-butene), whereas the formation of 1,3-dichloro-2-butene at the Brønsted sites of zeolite HZSM-5 was not observed. The mechanisms of 1,2-dichloroethane conversions at Lewis and Brønsted acid sites were proposed.
EFFECT OF THE ELECTRONIC STATE AND COPPER LOCALIZATION IN ZSM-5 PORES ON PERFORMANCE IN NO SELECTIVE CATALYTIC REDUCTION BY PROPANE
O.P. Krivoruchko, T.V. Larina, R.A. Shutilov, V.Yu. Gavrilov, S.A. Yashnik, V.A. Sazonov, I.Yu. Molina, Z.R. Ismagilov
Appl. Catal., B, 103(1-2) (2011) pp. 1-10.
This study was devoted to determination of localization of the individual copper species in the pores of ZSM-5 zeolite after post-synthetic zeolite modification by incipient wetness impregnation with CuCl2 solution followed by hydrolytic polycondensation of the ions in the pores. A series of Cu(n)ZSM-5 samples, where n is the copper concentration varied from 0.5 to 5.0 wt%, were synthesized using this method. A commercial HZSM-5 zeolite having Si/Al = 17 was used for the synthesis of the catalysts. After modification the Cu(n)ZSM-5 samples were dried and calcined in air at 110 and 450°C, respectively. The samples were studied by UV–vis–NIR DR spectroscopy, XRD and by measuring and processing the low-temperature (77 K) adsorption of nitrogen and hydrogen. It was shown for the first time that at the concentration of 1.0 wt% or lower copper was localized in the form of isolated Cu2+Oh cations in the ion-exchange positions in the zeolite micro- and mesopores as well as on oxygen complexes of extraframework aluminum in thin mesopores with D < 3.2 nm in the form of superficial spinel-like structures in octahedral oxygen coordination Cu2+Oh. At the copper concentration above 1.0 wt% linear associates of weakly bound Cu2+Oh ions with unusual orbital ordering were formed in addition to the two forms discussed above. These associates existing in the forms of one- and two-dimensional nanohydroxocompounds were localized partially in the zeolite micropores but mostly in thin mesopores.
The effect of the individual copper species on the catalytic properties of Cu(n)ZSM-5 samples in selective catalytic reduction of NO by propane was also studied. It was found that isolated Cu2+Oh cations in the ion-exchange positions and Cu2+Oh cations localized on the oxygen complexes of extraframework aluminum had the highest catalytic activity in NO SCR by propane. The weakly bound linear associates of Cu2+Oh ions had lower catalytic activity, compared with isolated Cu2+Oh ions. When their amount was high, they caused steric hindrance for contact of the reagents with the more active sites. The Cu2+Oh ion associates were found to transform to nanodispersed Cu2(OH)3Cl during catalytic experiments.
LOCATION, STABILITY, AND REACTIVITY OF OXYGEN SPECIES GENERATED BY N2O DECOMPOSITION OVER Fe-ZSM-5 AND Fe-Beta ZEOLITES
V.I. Sobolev, K.Yu. Koltunov
J. Mol. Catal. A: Chem., 347(1-2) (2011) pp. 22-27.
Reactivity of oxygen species generated by N2O decomposition over Fe-ZSM-5 and Fe-Beta zeolites was investigated using oxygen isotopic exchange as test reaction. The generated species are very stable up to 300°C in the absence of the organic traces or residual N2O in the gas phase. The reactivity of the oxygen species towards organics depends on the size of the organic molecules and their ability to penetrate into the zeolite pores. For example, in case of Fe-ZSM-5 zeolite, the oxygen species react readily with toluene, but stay intact with more bulky 1,3,5-trimethylbenzene.
MoVNbTe MIXED OXIDES AS EFFICIENT CATALYST FOR SELECTIVE OXIDATION OF ETHANOL TO ACETIC ACID
V.I. Sobolev, K.Yu. Koltunov
ChemCatChem, 3(7) (2011) pp. 1143-1145.
Results from a comparative study of the catalytic activity of MoVNb, MoVTe, and MoVNbTe mixed oxides in the gas phase oxidation of ethanol are reported. Multi-component MoVNbTe mixed oxides, analogous to those, which are used in the propane (amm)oxidation), in contrast to three-component MoVNb and MoVTe oxides show exclusive efficiency in selective oxidation of ethanol by molecular oxygen to obtain acetic acid.
GENERATION OF REACTIVE OXYGEN SPECIES ON Au/TiO2 AFTER TREATMENT WITH HYDROGEN: TESTING THE LINK TO ETHANOL LOW-TEMPERATURE OXIDATION
V.I. Sobolev, O.A. Simakova, K.Yu. Koltunov
ChemCatChem, 3(9) (2011) pp. 1422-1425.
In the present work, the efforts were focused on the role of hydrogen in the catalytic activity of gold supported on TiO2, Al2O3, and SiO2 matrixes to provide insights into the different profiles of ethanol oxidation.
JOINT AROMATIZATION OF BUTANE AND HEXANE ON ALUMINA–PLATINUM CATALYSTS
V.V. Pashkov*, D.V. Golinsky*, I.E. Udras*, E.A. Paukshtis, A.S. Belyi* (*Institute of Hydrocarbons Processing, Omsk, Russia)
Pet. Chem., 51(4) (2011) pp. 286-292.
It has been found that the joint aromatization of C4 and C6 alkanes proceeds during the conversion of a butane and hexane mixture on alumina–platinum catalysts. It has been shown that a necessary condition for realization of the joint aromatization is the presence of highly dispersed platinum as ionic species (Ptσ) and “hard” Lewis acid sites (Lz) of a catalyst. It has been determined that an optimum Lz/Ptσ ratio for joint conversion reaction of light alkanes is from 1 to 2.
ROLE OF DIFFERENT ACTIVE SITES IN HETEROGENEOUS ALKENE HYDROGENATION ON PLATINUM CATALYSTS REVEALED BY MEANS OF PARAHYDROGEN-INDUCED POLARIZATION
V.V. Zhivonitko*, K.V. Kovtunov*, I.E. Beck, A.B. Ayupov, V.I. Bukhtiyarov, I.V. Koptyug* (*International Tomography Center, Novosibirsk, Russia)
J. Phys. Chem. C, 115(27) (2011) pp. 13386-13391.
Substantial NMR signal enhancements provided by parahydrogen-induced polarization (PHIP) are associated with the ability of a catalyst to incorporate both H atoms of a dihydrogen molecule into the same product molecule. Therefore, PHIP can provide valuable information about the mechanisms and kinetics of catalytic hydrogenation reactions as well as produce hyperpolarized molecules for sensitivity enhancement in NMR. In this work, the PHIP technique was applied to study the structure sensitivity and the support effects on the degree of pairwise H2 addition in propene hydrogenation over supported platinum catalysts. Four series of Pt catalysts supported on Al2O3, SiO2, ZrO2, and TiO2 were examined. A nontrivial dependence of the selectivity toward pairwise H2 addition on the Pt particle size was found. Its analysis indicates that at least three types of different active sites coexist on the catalysts surface. Among them, the major one is responsible for the nonpairwise H2 addition to the double bond, whereas pairwise addition can proceed on the other two minor active sites. An explanation of the nature of these active sites is proposed. A substantial increase in the pairwise addition selectivity was found for Pt/TiO2 catalysts as compared to other catalyst series, possibly due to a strong metal―support interaction taking place even after low temperature catalyst reduction.
CHARACTERIZATION OF ACTIVE SITES OF Pd/Al2O3 MODEL CATALYSTS WITH LOW Pd CONTENT BY LUMINESCENCE, EPR AND ETHANE HYDROGENOLYSIS
A.A. Vedyagin, A.M. Volodin, V.O. Stoyanovskii, D.A. Medvedev, A.S. Noskov
Appl. Catal., B, 103(3-4) (2011) pp. 397-403.
Spectroscopic (laser-induced luminescence (LIL) and EPR) and catalytic (ethane hydrogenolysis) techniques were used for characterization of the active sites of Pd/Al2O3 catalysts. These techniques have high sensitivity and make it possible to study the catalysts with Pd concentrations as low as 0.02–0.03 wt%. It was found by EPR using spin probes that the electron donor sites of the support are modified by the deposited palladium. It was found by LIL that the Pd deposition has a substantial effect on the state of hydroxyls on the Al2O3 surface. The obtained results indicate that at Pd concentrations 0.5 wt% or lower supported Pd does not form PdO phase. Instead, it is stabilized in the form of atomically dispersed ion clusters. The possible role of the Al2O3 donor sites in stabilization of such clusters is discussed.
STRUCTURAL AND CHEMICAL STATES OF PALLADIUM IN Pd/Al2O3 CATALYSTS UNDER SELF-SUSTAINED OSCILLATIONS IN REACTION OF CO OXIDATION
E.M. Slavinskaya, O.A. Stonkus, R.V. Gulyaev, A.S. Ivanova, V.I. Zaikovsky, P.A. Kuznetsov, A.I. Boronin
Appl. Catal., A, 401(1-2) (2011) pp. 83-97.
Pd/Al2O3 supported catalysts, differed in the initial structural and chemical states of palladium, were examined for the possible existence of self-sustained oscillations in the reaction of CO oxidation under temperature-programmed and isothermal modes using plug flow reactor at ambient pressure and CO and O2 concentration of 0.2 and 1.0 vol.%, respectively. The supported samples after the action of reaction mixture were characterized using the HRTEM and XPS methods. The catalysts, calcined at relatively low temperatures 450°C, cannot induce the self-sustained oscillation phenomena in the reaction of CO oxidation. The calcination at 800°C yields highly dispersed particles of Pd0 and PdO in the catalysts with sizes varying between 2–3 and 10–20 nm, respectively. In this case self-sustained oscillations (SO) of the CO oxidation appeared in the region of middle CO conversions. In the catalyst calcined at 1000°C, PdO is formed as large particles with sizes 20–100 nm. During prolonged self-sustained oscillations under isothermal conditions with varying CO concentrations in the reaction mixture, particles with “core–shell” structures are formed, where the cores are PdO and the shells are a Pd0 clusters ordered along a specific direction due to an epitaxy on PdO. Calcination at 1200°C results in the formation of large Pd0 particles with sizes ≥200 nm. During prolonged self-sustained oscillations with varying CO concentrations under isothermal conditions, the reaction mixture causes destruction of the above particles to yield palladium particles with core–shell structures; in this case the cores are Pd0, and the shells are PdO layers.
LOW-TEMPERATURE OXIDATION OF CARBON MONOXIDE ON Pd(Pt)/CeO2 CATALYSTS PREPARED FROM COMPLEX SALTS
E.M. Slavinskaya, R.V. Gulyaev, O.A. Stonkus, A.V. Zadesenets*, P.E. Plyusnin*, Yu.V. Shubin*, S.V. Korenev*, A.S. Ivanova, V.I. Zaikovsky, I.G. Danilova, A.I. Boronin (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
Kinet. Catal., 52(2) (2011) pp. 282-295.
Catalysts containing cerium oxide as a support and platinum and palladium as active components for the low-temperature oxidation of carbon monoxide were studied. The catalysts were synthesized in accordance with original procedures with the use of palladium and platinum complex salts. Regardless of preparation procedure, the samples prepared with the use of only platinum precursors did not exhibit activity at a low temperature because only metal and oxide (PtO, PtO2) nanoparticles were formed on the surface of CeO2. Unlike platinum, palladium can be dispersed on the surface of CeO2 to a maximum extent up to an almost an ionic (atomic) state, and it forms mixed surface phases with cerium oxide. In a mixed palladium-platinum catalyst, the ability of platinum to undergo dispersion under the action of palladium also increased; as a result, a combined surface phase with the formula PdxPtyCeO2-δ, which exhibits catalytic activity at low temperatures, was formed.
SYNERGETIC EFFECT IN PdAu/CeO2 CATALYSTS FOR THE LOW-TEMPERATURE OXIDATION OF CO
R.V. Gulyaev, L.S. Kibis, O.A. Stonkus, A.V. Zadesenets*, P.E. Plyusnin*, Yu.V. Shubin*, S.V. Korenev*, A.S. Ivanova, E.M. Slavinskaya, V.I. Zaikovsky, I.G. Danilova, A.I. Boronin (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
J. Struct. Chem., 52(suppl.) (2011) pp. 123-136.
Gold-palladium catalysts supported on cerium oxide were synthesized with the double complex salts. X-ray photoelectron spectroscopy (XPS) and other physicochemical methods (TEM, TPR) were used to demonstrate that synthesis of highly active palladium catalysts requires the oxidative treatment stimulating the formation of a catalytically active surface solid solution PdxCe1-xO2, which is responsible for the low-temperature activity (LTA) in the reaction CO + O2. In the case of gold catalysts, active sites for the low-temperature oxidation of CO are represented by gold nanoparticles and its cationic interface species. Simultaneous deposition of two metals increases the catalyst LTA due to interaction of both gold and palladium with the support surface to form a Pd1-xCexO2 solid solution and cationic interface species of palladium and gold on the boundary of Pd-Au alloy particles anchored on the solid solution surface.
DYNAMIC Cu/Zn INTERACTION IN SiO2 SUPPORTED METHANOL SYNTHESIS CATALYSTS UNRAVELED BY in situ XAFS
D. Grandjean*,**, V.V. Pelipenko, E.D. Batyrev***, J.C. van den Heuvel***,
A.A. Khassin, T.M. Yurieva, B.M. Weckhuysen** (*Laboratory of Solid State Physics and Magnetism & INPAC, Leuven, Belgium; **Utrecht University, Utrecht, The Netherlands; ***University of Amsterdam, Amsterdam, The Netherlands)
J. Phys. Chem. C, 115(41) (2011) pp. 20175-20191.
In situ X-ray absorption spectroscopy XAFS at the Cu and Zn K-edge has been used to unravel the Cu/Zn interaction and identify the possible active site of Cu-based methanol synthesis catalysts in the Cu/ZnO/SiO2 ternary system. These highly dispersed silica supported catalysts, whose activity increases sharply as a function of the reduction temperature, were studied calcined, reduced at 200, 300, and 400°C, and for each reduction temperature under passivation/rereduction and methanol synthesis conditions. Results showed that the calcined form consists mainly of a mixed Cu/Zn hydrosilicate that is progressively transformed as the reduction temperature increases into (i) Cu metal particles, (ii) increasingly dispersed ZnO species on SiO2, and (iii) finally a Zn metallic phase forming segregated bimetallic Cu–Zn α-brass alloy particles. These different structures and Cu/Zn interfaces may correspond to different active phases and activities in methanol synthesis. After reduction at 200 and 300°C, Cu0 is likely composing most of the active phase, whereas above 300°C, the sharp increase in the number Zn0-based sites formed as a function of the reduction temperature could explain the major role played by this parameter in controlling the activity of these catalysts. The dynamic Cu/Zn interaction as a function of the temperature and gas environment
pointed out in this ternary system may be at the origin of the existence of different and sometimes contradictory models to account for the mechanisms of the methanol synthesis.
CHARACTERIZATION OF THE ACTIVE SITES ON THE SURFACE OF Al2O3 ETHANOL DEHYDRATION CATALYSTS BY EPR USING SPIN PROBES
R.A. Zotov, V.V. Molchanov, A.M. Volodin, A.F. Bedilo
J. Catal., 278(1) (2011) pp. 71-77.
Several pure and doped alumina samples were characterized by EPR using spin probes and tested in ethanol dehydration. It was found that the concentrations of the electron acceptor sites and the catalytic activity increased when alumina was modified with chlorides and sulfates. Meanwhile, the number of the electron donor sites decreased. A very good correlation between the concentration of the weak acceptor sites and the catalytic activity of the acid-modified catalysts almost passing through the origin of the coordinates was obtained for all the studied samples. Alumina poisoning with sodium resulted in the decrease in the catalytic activity and the concentration of the weak acceptor sites. Therefore, it appears that the weak acceptor sites tested using anthracene are related to the sites active in the ethanol dehydration reaction.
INVESTIGATION OF OXYGEN STATES AND REACTIVITIES ON A NANOSTRUCTURED CUPRIC OXIDE SURFACE
D.A. Svintsitskiy, A.I. Stadnichenko, D.V. Demidov, S.V. Koshcheev, A.I. Boronin
Appl. Surf. Sci., 257(20) (2011) pp. 8542-8549.
Nanostructured copper (II) oxide was formed on clean copper foil at room temperature using activated oxygen produced by RF discharge. CuO particles of approximately 10-20 nm were observed on the surface by Scanning Tunneling Microscopy (STM). The copper states and oxygen species of the model cupric oxide were studied by means of X-ray Photoelectron Spectroscopy (XPS). These oxide particles demonstrated abnormally high reactivity with carbon monoxide (CO) at temperatures below 100°C. The XPS data showed that the interaction of CO with the nanostructured cupric oxide resulted in reduction of the CuO particles to Cu2O species. The reactivity of the nanostructured cupric oxide to CO was studied at 80°C using XPS in step-by-step mode. The initial reactivity was estimated to be 5 x 10-5 and was steadily reduced down to 5 x 10-9 as the exposure was increased. O1s spectral analysis allowed to propose that the high initial reactivity was caused by the presence of non-lattice oxygen states on the surface of the nanostructured CuO. It was established that reoxidation of the partially reduced nanostructured cupric oxide by molecular oxygen O2 restored the highly reactive oxygen form on the surface. These results allowed to propose that the nanostructured cupric oxide could be used for low temperature catalytic CO oxidation. Some hypotheses concerning the nature of the non-lattice oxygen species with high reactivity are also discussed.
Fe-CONTAINING NICKEL PHOSPHATE MOLECULAR SIEVES AS HETEROGENEOUS CATALYSTS FOR PHENOL OXIDATION AND HYDROXYLATION WITH H2O2
M.N. Timofeeva, Z. Hasan*, A.Yu. Orlov, V.N. Panchenko, Yu.A. Chesalov, I.E. Soshnikov, Sung H. Jhung* (*Kyungpook National University, Taegu, South Korea)
Appl. Catal., B, 107(1-2) (2011) pp. 197-204.
Fe-containing nickel phosphate molecular sieves (Fe-VSB-5) were hydrothermally synthesized in weak basic conditions under microwave irradiation and characterized by SEM, XRD,
N2-adsorption/desorption, DRS-UV–vis, and FT-IR spectroscopy using PhCN and CDCl3 as probe molecules. The catalytic activity of Fe-VSB-5 was tested for the phenol hydroxylation and wet phenol oxidation with H2O2. The increase in iron content in Fe-VSB-5 leds to an increase in the reaction rates. The increases in activity can be explained by the role of the Fe species, which increases the generation of radicals. The Fe-VSB-5 samples were stable against the leaching out of Fe ions. The catalytic activity of Fe-VSB-5 was compared to the catalytic activity of traditional Fe-containing materials.
CATALYTIC ROLE OF O•– RADICALS IN THE LOW-TEMPERATURE ISOTOPIC EXCHANGE IN DIOXYGEN
E.V. Starokon, M.V. Parfenov, S.E. Malykhin, G.I. Panov
J. Phys. Chem. C, 115(25) (2011) pp. 12554-12559.
In spite of a long investigation history, the low-temperature isotopic exchange in dioxygen taking place without involvement of the catalyst oxygen (R0 exchange) is still an exotic and poorly understood phenomenon in heterogeneous catalysis. Although very strong bonds are to be cleft in O2 molecules (118 kcal/mol), over some metal oxides R0 can be observed even at the temperature of liquid nitrogen. In this work, the authors studied the R0 exchange over a FeZSM-5 zeolite at 233 K and discovered for the first time a linear dependence of the R0 rate on the concentration of O•– radicals (a-oxygen), which identifies a catalytic role of these species. Upon transition to cryogenic temperatures, O•– species lose the ability to exchange themselves with dioxygen, but start functioning as a principal part of unique active sites capable of catalyzing a very smooth redistribution of the oxygen-oxygen bonds in adsorbed O2 molecules. Running by a highly concerted mechanism, this remarkable process leads to the R0 exchange with almost zero activation energy (0.2 kcal/mol). The catalytic role of O•– radicals well explains all previous results obtained for the R0 exchange in the literature. Possible models of active sites comprising O•– species are discussed.
ROOM-TEMPERATURE OXIDATION OF METHANE BY a-OXYGEN AND EXTRACTION OF PRODUCTS FROM THE FeZSM-5 SURFACE
E.V. Starokon, M.V. Parfenov, L.V. Piryutko, S.I. Abornev, G.I. Panov
J. Phys. Chem. C, 115(5) (2011) pp. 2155-2161.
Room-temperature oxidation of methane to methanol by a-oxygen is of great mechanistic interest for both conventional and biomimetic oxidation catalysis. This work was carried out using new-generation FeZSM-5 samples that have the Oa concentration of 100 umol/g. This value exceeds 3-15 times the Oa concentration on the earlier studied samples, thus providing more precise quantitative measurements related to the reaction mechanism. Fourier transform infrared spectroscopy data confirmed an earlier conclusion that CH4 + Oα surface reaction proceeds by the hydrogen abstraction mechanism. This mechanism leads to hydroxy and methoxy groups residing on α-sites. The methanol formation takes place by hydrolysis of (Fe-OCH3)α groups at the step of extraction. For the first time dimethyl ether (DME) was identified in the reaction products, its amount comprising 6-7% of the methane reacted. In distinction to methanol, DME is readily extracted both by dry solvents (acetonitrile, tetrahydrofuran, ethanol) and their mixtures with water. A reliable extraction procedure was developed, which provides a 75% recovery of the methane oxidation products (methanol + DME). The missing products are shown to remain on the catalyst surface and can be quantitatively recovered in the form of COx at heating the sample. A mechanism involving CH3• radicals formed in the H-abstraction step is suggested to explain the reaction stoichiometry CH4:Oα = 1:1.75 and a deficit of the carbon balance at extraction.
KINETICS AND MECHANISM OF THE HOMOGENEOUS OXIDATION OF n-BUTENES TO METHYL ETHYL KETONE IN A SOLUTION OF Mo-V-PHOSPHORIC HETEROPOLY ACID IN THE PRESENCE OF PALLADIUM
V.F. Odyakov, E.G. Zhizhina
Kinet. Catal., 52(6) (2011) pp. 828-834.
In catalytic two-step n-butene oxidation with dioxygen to methyl ethyl ketone, the first step is the oxidation of n-C4H8 with an aqueous solution of Mo–V–P heteropoly acid in the presence of Pd(II) complexes. The kinetics of n-butene oxidation with solutions of H7PV4Mo8O40 (HPA-4) in the presence of the Pd(II) dipicolinate complex (H2O)PdII(dipic) (I), where dipic2– is the tridentate ligand 2,6-NC5H3(COO–)2, is studied. Calculation shows that, at the ratio dipic2– : Pd(II) = 1 : 1, the ligand decreases the redox potential of the Pd(II)/Pdmet system from 0.92 to 0.73–0.77, due to which Pd(II) is stabilized in reduced solutions of HPA-4. The reaction is first-order with respect to n-C4H8. Its order with respect to Pd(II) is slightly below unity, and its order with respect to HPA-4 is relatively low (~0.63). The activation energy of but-1-ene oxidation in the temperature range from 40 to 80°C is 49.0 kJ/mol, and that of the oxidation of but-2-ene is 55.6 kJ/mol. The mechanism of the reaction involving the cis-diaqua complex [(H2O)2PdII(Hdipic)]+, which forms reversibly from complex I, is proposed. The reaction rate is shown to increase with an increase in the HPA-4 concentration due to an increase in the acidity of the solution.
PARTIAL OXIDATION OF METHANE ON Pt-SUPPORTED LANTHANIDE DOPED CERIA–ZIRCONIA OXIDES: EFFECT OF THE SURFACE/LATTICE OXYGEN MOBILITY ON CATALYTIC PERFORMANCE
V.A. Sadykov, N.N. Sazonova, A.S. Bobin, V.S. Muzykantov, E.L. Gubanova*, G.M. Alikina, A.I. Lukashevich, V.A. Rogov, E.N. Ermakova, E.M. Sadovskaya, N.V. Mezentseva, E.G. Zevak, S.A. Veniaminov, M. Muhler*, C. Mirodatos**, Y. Schuurman**, A.C. van Veen*,** (*Ruhr-Universität Bochum, Bochum, Germany; **Institut de Recherches sur la Catalyse et L’environnement de Lyon, Villeurbanne Cedex, France)
Catal. Today, 169(1) (2011) pp. 125-137.
Partial oxidation of methane into syngas at short contact times (5–15 ms) was studied in both steady-state and transient modes at temperatures up to 850°C in realistic feeds (CH4 content up to 20%, CH4/O2 = 2) with a minimum impact of mass and heat transfer for structured catalysts carrying Pt/Ln0.3Ce0.35Zr0.35O2-y (Ln = La, Pr, Gd) as thin layers on walls of corundum channel substrates. Oxygen mobility and reactivity of the active phase were characterized by oxygen isotope heteroexchange, temperature-programmed O2 desorption and CH4 reduction, isothermal pulse reduction by methane with wide variation of CH4 concentrations and TAP pulse studies. Experimental data point towards a selective oxidation of methane into syngas via a direct route with oxygen-assisted methane activation. This mechanistic feature is related to the strong Pt-support interaction stabilizing highly dispersed oxidic Pt species less active in CH4 and syngas combustion than metallic Pt clusters. Support activates O2 molecules and supplies active oxygen species to Pt sites. A high rate of oxygen diffusion on the surface and in the bulk of the support and Pt-support oxygen spillover stabilizes Pt in a well dispersed partially oxidized state while preventing coking at high concentrations of CH4 in the feed.
DRY REFORMING OF METHANE OVER Pt/PrCeZrO CATALYST: KINETIC AND MECHANISTIC FEATURES BY TRANSIENT STUDIES AND THEIR MODELING
V.A. Sadykov, E.L. Gubanova, N.N. Sazonova, S.A. Pokrovskaya, N.A. Chumakova, N.V. Mezentseva, A.S. Bobin, R.V. Gulyaev, A.V. Ishchenko, T.A. Krieger, C. Mirodatos*
(*Institut de Recherches sur la Catalyse et L’environnement de Lyon, Villeurbanne Cedex, France)
Catal. Today, 171(1) (2011) pp. 140-149.
The effect of pretreatment and Pt content on the catalytic properties as well as mechanistic features of DR were investigated for structured catalysts comprised of Pt supported on CeO2-ZrO2 oxide doped by Pr. Progressive reduction of cationic Pt species by the reaction feed lowers the activity in CH4 dry reforming while accelerating the reverse water gas shift reaction catalyzed only by Pt(0), which then decreases progressively the H2/CO ratio in the effluent. This process is counteracted by the mobility of surface oxygen supplying oxygen atoms to reduced Pt centers thus ensuring their reoxidation and generating in parallel surface oxygen vacancies for the dissociation of CO2.
A mathematical model and software were developed for numerically studying the transients of the complex catalytic reactions. The processing of experimental data was fulfilled taking into account the importance of cationic forms of Pt, reactivity of carbonate complexes coordinated to these cations and oxygen surface/bulk diffusion. A quantitative evaluation of the density of catalyst's active sites and their coverage by reactive species was accomplished and the rates both of the lattice oxygen diffusion and main stages of the catalytic reaction were estimated.
DRY REFORMING OF METHANE OVER LnFe0.7Ni0.3O3-δ PEROVSKITES: INFLUENCE OF Ln NATURE
L.G. Kapokova, S.N. Pavlova, R.V. Bunina, G.M. Alikina, T.A. Krieger, A.V. Ishchenko, V.A. Rogov, V.A. Sadykov
Catal. Today, 164(1) (2011) pp. 227-233.
LnFe0.7Ni0.3O3-δ (Ln = La, Pr, Sm) perovskites synthesized via Pechini method have been studied as catalysts of methane dry reforming (MDR). Effects of pretreatment and type of Ln cation on the structural and redox properties of perovskites and their catalytic performance have been elucidated. The most active catalysts are obtained by keeping perovskites in the reaction feed at high temperatures due to the formation of Ni–Fe alloy particles released from the perovskite lattice and stabilized on its surface. PrFe0.7Ni0.3O3-δ was found to be the most active and stable catalyst due to the optimal composition of segregated Ni–Fe alloy particles and redox properties of oxide matrix.
FORMATION OF PLATINUM SITES ON LAYERED DOUBLE HYDROXIDES TYPE BASIC SUPPORTS: I. EFFECT OF THE NATURE OF THE INTERLAYER ANION ON THE STRUCTURE CHARACTERISTICS OF THE LAYERED ALUMINUM–MAGNESIUM HYDROXIDE AND THE FORMATION OF AN OXIDE PHASE
O.B. Belskaya*,**, N.N. Leont’eva*, T.I. Gulyaeva*, V.A. Drozdov*,**, V.P. Doronin*,**, V.I. Zaikovsky, V.A. Likholobov* (*Institute of Hydrocarbons
Processing, Omsk, Russia; **Omsk State Technical University, Omsk, Russia)
Kinet. Catal., 52(5) (2011) pp. 761-769.
A layered aluminum–magnesium hydroxide of the hydrotalcite type containing interlayer carbonate counterions (HT-CO3) and activated hydrotalcite containing interlayer OH– ions (HT-OH) were studied for the subsequent use as the precursors of supports for platinum catalysts. It was found that the nature of an interlayer anion in the composition of an aluminum–magnesium layered hydroxide is an important factor affecting both the formation of the oxide support and its texture characteristics. The replacement of the interlayer anion by OH– resulted in changes in the structural parameters of the initial double hydroxide: a decrease in the interlayer distance with the retention of the Mg/Al ratio and an increase in the imperfection of the layered material. X-ray diffraction studies in the temperature range of 30– 900°C showed that HT-OH is characterized by the ability to form low-temperature spinel at 375°C. As a result, two types of aluminum–magnesium oxide supports, which were characterized by different pore space organizations at the same Mg : Al ratio, were obtained from the given layered hydroxides.
HYDROISOMERIZATION OF BENZENE-CONTAINING GASOLINE FRACTIONS ON A Pt/SO42-–ZrO2–Al2O3 CATALYST: II. EFFECT OF CHEMICAL COMPOSITION ON ACIDIC AND HYDROGENATING AND THE OCCURRENCE OF MODEL ISOMERIZATION REACTIONS
M.O. Kazakov*, A.V. Lavrenov*, I.G. Danilova, O.B. Belskaya*, V.K. Duplyakin* (*Institute of Hydrocarbons Processing, Omsk, Russia)
Kinet. Catal., 52(4) (2011) pp. 573-578.
The acidic and hydrogenating of Pt/SO42-–ZrO2–Al2O3 samples containing from 18.8 to 67.8 wt% Al2O3 as a support constituent were studied by the IR spectroscopy of adsorbed CO and pyridine, and the model reactions of n-heptane and cyclohexane isomerization on these catalysts were examined. The total catalyst activity in the conversion of n-heptane decreased with the concentration of Al2O3; this manifested itself in an increase in the temperature of 50% n-heptane conversion from 112 to 266°C and in an increase in the selectivity of isomerization to 94.2%. In this case, the maximum yield of isoheptanes was 47.1 wt%, which was reached on a sample whose support contained 67.8 wt% Al2O3. A maximum yield (69.6 wt%) and selectivity (93.7%) for methylcyclopentane formation from cyclohexane were also reached on the above catalyst sample. This can be explained by lower concentrations of Lewis and Bronsted acid sites in the Pt/SO42-–ZrO2–Al2O3 system, as compared with those in Pt/SO42-–ZrO2. The experimental results allowed to make a preliminary conclusion that the Pt/SO42-–ZrO2–Al2O3 catalyst whose support contains 67.8 wt% Al2O3 is promising for use in the selective hydroisomerization of benzene-containing gasoline fractions in the thermodynamically favorable process temperature range of 250–300°C.
FORMATION OF PLATINUM SITES ON LAYERED DOUBLE HYDROXIDE TYPE BASIC SUPPORTS: II. EFFECT OF THE NATURE OF THE INTERLAYER ANION OF THE LAYERED ALUMINUM-MAGNESIUM HYDROXIDES ON PLATINUM BINDING AND Pt/MgAlOx FORMATION
O.B. Belskaya*, T.I. Gulyaeva*, N.N. Leont’eva*, V.I. Zaikovsky, T.V. Larina, T.V. Kireeva*, V.P. Doronin*, V.A. Likholobov* (*Institute of Hydrocarbons Processing, Omsk, Russia)
Kinet. Catal., 52(6) (2011) pp. 876-885.
The interaction of aqueous H2PtCl6 solutions with hydrotalcite-type aluminum–magnesium
hydroxides differing in the nature of their interlayer anion is reported. In the case of CO32- as the interlayer anion, the introduction of the platinum(IV) chloro complex does exerts no significant effect on the structural properties of the support, on its thermal decomposition dynamics, and on the textural characteristics of the resulting oxide phase. The binding of the platinum complexes to “activated hydrotalcite” with interlayer OH– anions increases the interplanar spacing and enhances the thermal stability of the layered structure. This is accompanied by marked changes in textural characteristics of the material, leading to the formation of a nearly monodisperse mixed oxide phase. In the Pt/MgAlOx samples obtained by reductive treatment, a considerable proportion of platinum is in the form of planar particles, and this corroborates the hypothesis that the metal complex at the sorption stage is mainly localized in the interlayer space of this support. Platinum binds to the support as chloro complexes via rapid anion exchange, and these bound platinum species are characterized by a higher reduction temperature.
COBALT OXIDE CATALYST FOR HYDROLYSIS OF SODIUM BOROHYDRIDE AND AMMONIA BORANE
V.I. Simagina, O.V. Komova, A.M. Ozerova, O.V. Netskina, G.V. Odegova, D.G. Kellerman*, O.A. Bulavchenko, A.V. Ishchenko (*Institute of Solid State Chemistry, Yekaterinburg, Russia)
Appl. Catal., A, 394(1-2) (2011) pp. 86-92.
The catalytic properties of Co3O4 in NaBH4 and NH3BH3 hydrolysis have been studied. Experiments were carried out at 20–40°C using 0.12 M hydride solution. According to magnetic susceptibility measurements, FTIR, XRD, and TEM studies, Co3O4 is reduced to the ferromagnetic catalytically active Co2B phase under the action of the NaBH4 hydrolysis reaction medium. A correlation was found between the content of the cobalt boride phase formed in situ and catalyst activity. The reduction of Co3O4 in NH3BH3 proceeds at slower rate than in NaBH4. The addition to a solution of NH3BH3 of even a small amount of NaBH4 increases considerably the reduction rate of Co3O4. Using a Co3O4-based precursor instead of the widely used CoCl2 leads to the formation of a stable catalytically active phase of cobalt boride.
LOW-TEMPERATURE DECOMPOSITION OF AMMONIA BORANE IN THE PRESENCE OF TITANIA
O.V. Komova, V.I. Simagina, G.V. Odegova, Yu.A. Chesalov, O.V. Netskina, A.M. Ozerova
Inorg. Mater., 47(10) (2011) pp. 1101-1107.
In the presence of anatase, the thermal decomposition of ammonia borane (AB) begins at a lower temperature, which enables AB dehydrogenation at a temperature as low as 80°C. The reduction in the AB decomposition temperature depends on the AB content of the mixture. In situ IR spectroscopy data demonstrate that, in the presence of TiO2, the structural destabilization of AB occurs during heating and is accompanied by the formation of an oxygen-containing boron phase and partial reduction of the titania, which is supported by diffuse reflectance spectroscopy data.
EFFECT OF THE REACTION MEDIUM ON THE STRUCTURE OF THE La1-xCaxMnO3 (x = 0–1) SOLID SOLUTIONS PREPARED BY THE PECHINI METHOD
L.A. Isupova, E.Yu. Gerasimov, V.I. Zaikovsky, S.V. Tsybulya
Kinet. Catal., 52(1) (2011) pp. 104-110.
The phase composition and microstructure of La1-xCaxMnO3 (x = 0–1) materials prepared by the Pechini method from polymer-salt stocks were studied after testing these materials in methane oxidation. According to X-ray diffraction data, the reaction medium causes no significant changes in the samples, while high-resolution transmission electron microscopy indicates that the x > 0.3 samples are
unstable. Under the action of the reaction medium, the perovskite structure of these samples undergoes partial decomposition accompanied by the formation of planar defects having a lower manganese content. The number and degree of segregation of these defects increase with increasing calcium content. The calcium oxide and manganese oxide phases as segregated nanoparticles are observed on the particle surface. These changes are caused by the decrease in the oxygen content of the manganites under the action of the reaction medium (T, PO2), by the formation of vacancies, and by the variation of the charge of the manganese cations, as well as by the charge ordering tendency of the manganese cations. Therefore, the observed changes in catalytic activity under the action of the reaction medium for x > 0.3 can be due to perovskite decomposition accompanied by the formation of planar defects, the release of the manganese oxide and calcium oxide phases, and their subsequent sintering.
INTERACTION OF HYDROGEN AND WATER WITH OXYGEN ADSORBED ON SILVER
E.V. Dokuchits, A.V. Khasin, A.A. Khassin
React. Kinet. Mech. Catal., 103(2) (2011) pp. 261-266.
The identity of surface silver hydroxides produced by hydrogenation or hydration of surface silver oxide was demonstrated. A two-route mechanism of hydrogen interaction with oxygen adsorbed on silver was suggested. The first route includes two consecutive-parallel steps: formation of adsorbed hydroxyl groups and their interaction with hydrogen; the second route consists of two consecutive steps: formation of adsorbed hydroxyl groups and their disproportionation yielding water and adsorbed oxygen.
COMPOSITION AND PROPERTIES OF FUNCTIONAL GROUPS ON SURFACE OF CARBON SORBENTS MODIFIED BY AMINOCAPROIC ACID
V.A. Likholobov*, L.G. P’yanova*, A.I. Boronin, S.V. Koshcheev, A.N. Salanov, O.N. Baklanova*, O.A. Knyazheva*, A.V. Veselovskaya* (*Institute of Hydrocarbons Processing, Omsk, Russia)
Prot. Met. Phys. Chem. Surf., 47(2) (2011) pp. 181-190.
The composition and properties of functional groups on the surface of carbon sorbents modified with aqueous solutions of aminocaproic acid of different concentrations were studied using physicochemical analysis methods including: acid-base titration, the Kjeldahl method, scanning electron microscopy, X-ray microanalysis, and X-ray photoelectron spectroscopy. The initial carbon sorbent was shown to have almost no functional groups on its surface. It was ascertained that the surface functionalization of carbon sorbent results in a change in microstructure and an increase in the amount of oxygen- and nitrogen-containing groups with increasing concentration of the modifying agent followed by its further polycondensation on the surface. According to the XPS data, the formation of the bond between aminocaproic acid and the carbon surface of sorbents occurs via a carboxylic group.
IDENTIFICATION OF NITROGEN-CONTAINING SPECIES OBTAINED BY NITRIC OXIDE ADSORPTION ON THE SURFACE OF MODEL GOLD CATALYSTS
A.V. Bukhtiyarov, A.V. Nartova, R.I. Kvon
Kinet. Catal., 52(5) (2011) pp. 756-760.
Nitric oxide adsorption at 300–500 K on gold particles supported on an alumina film has been investigated for the first time by in situ X-ray photoelectron spectroscopy. Two nitrogen-containing adsorption species can form on the surface of gold particles. By test experiments on NO adsorption on the stepped face (533) of a gold single crystal, these species have been identified as adsorbed nitrogen atoms (which are detected throughout the temperature range examined) and a surface complex with N2O stoichiometry (which is stable in a narrow temperature range of 325–425 K).
AN XPS AND STM STUDY OF THE SIZE EFFECT IN NO ADSORPTION ON GOLD NANOPARTICLES
A.V. Bukhtiyarov, A.V. Nartova, R.I. Kvon, V.I. Bukhtiyarov
Russ. Chem. Bull., 60(10) (2011) pp. 1977-1984.
The effect of the gold particle size, temperature of the model gold catalyst, and NO pressure on the composition of the adsorption layer was studied by in situ XPS and STM methods. Adsorption of nitric oxide was carried out on gold nanoparticles with a mean size of 2–7 nm prepared on the thin film surface of alumina. In high-vacuum conditions (P NO ≈ 10-5 Pa), only atomically adsorbed nitrogen is formed on the surface of gold nanoparticles. At about 1 Pa pressure of NO and in the temperature range from 325 to 475 K, atomically adsorbed nitrogen coexists with the N2O adsorption complex. The surface concentration of the adsorbed species changes with a change in both the mean gold particle size and adsorption temperature. The saturation coverage of the surface with the nitrogen-containing complexes is observed for the sample with a mean size of gold particles of 4 nm. The surface of these samples is mainly covered with atomically adsorbed nitrogen, the saturation coverage of adsorbed nitrogen of about ∼0.6 monolayer is attained at T = 473 K. The change in the composition of the adsorption layer with temperature of the catalysts agrees with the literature data on the corresponding temperature dependence of the selectivity of N2 formation observed in the catalytic reduction of NO with carbon monoxide on the Au/Al2O3 catalyst. The dependences of the composition of the adsorption layer on the mean size of Au nanoparticles (size effect) and temperature of the catalyst are explained by the sensitivity of NO adsorption to specific features of the gold surface.
MECHANISM OF H2-PROMOTED OXIDATION OF NITROGEN MONOXIDE OVER Ag/Al2O3
N.A. Sadokhina*, A.V. Bukhtiyarov, A.I. Mytareva*, R.I. Kvon, V.I. Bukhtiyarov, A.Yu. Stakheev* (*Zelinsky Institute of Organic Chemistry, Moscow, Russia)
Mendeleev Commun., 21(5) 2011 pp. 274-276.
H2-promoted oxidation of NO to NO2 over Ag/Al2O3 proceeds via two-step echanism:
(1) formation of surface nitrate species, and
(2) reduction of this species with NO. Hydrogen plays a crucial role at the first step.
H2-INDUCED NOx ADSORPTION/ DESORPTION OVER Ag/Al2O3: TRANSIENT EXPERIMENTS AND TPD STUDY
N.A. Sadokhina*, D.E. Doronkin*, P.V. Pributkov*, V.I. Bukhtiyarov, R.I. Kvon, A.Yu. Stakheev* (*Zelinsky Institute of Organic Chemistry, Moscow, Russia)
Top. Catal., 54(16-18) (2011) pp. 1190-1196.
NO adsorption/desorption over 1 wt% Ag/Al2O3 was studied by a combination of isothermal transient adsorption/desorption and NOx temperature-programmed desorption (NOx-TPD) methods. NOx-TPD profiles obtained for Ag/Al2O3 were identified by comparison with decomposition profiles of “model” AgNO3/Al2O3 and Al(NO3)3/Al2O3 prepared by impregnation of Al2O3 with individual AgNO3 and Al(NO3)3 compounds. The data obtained indicate that H2-induced NO adsorption leads to the formation of surface Ag and Al-nitrates. Their accumulation on the catalyst surface is accompanied by an intensive NO2 evolution, which proceeds primarily via reaction of surface nitrates with NO. Thus, NO2 formation appears to result from an intrinsic stage of the H2-induced NOx adsorption process, rather than from the direct oxidation of NO by gaseous oxygen catalyzed by Ag.
CONCENTRATION HYSTERESIS IN METHANE OXIDATION ON NANOSIZED PLATINUM PARTICLES
I.Yu. Pakharukov, I.E. Beck, M.M. Matrosova, V.I. Bukhtiyarov, V.N. Parmon
Doklady Phys. Chem., 439(1) (2011) pp. 131–134.
Study of hysteresis is an efficient tool for investigating the catalytic process mechanism. In the work it was for the first time detected the concentration hysteresis in low-temperature methane oxidation on a dispersed Pt/γ-Al2O3 catalyst with an average platinum particle size of 2 nm.
GAS PHASE NITRIDATION OF SILICATE FIBER GLASS MATERIALS WITH AMMONIA: THREE CASE STUDIES
Yu.K. Gulyaeva, A.P. Suknev, E.A. Paukshtis, B.S. Bal’zhinimaev,
J. Non-Cryst. Solids, 357(18) (2011) pp. 3338-3344.
Three types of the leached fiber glass materials of silicate origin modified with Zr, Al and rare earth metals (REM) were nitridated with ammonia at temperatures ranging from 673 to 973 K. DRIFTS (Diffuse Reflectance Infrared Fourier-Transform Spectroscopy) and H/D exchange using ND3 were applied for characterization of the formed NH species. Along with nitridation of silanol groups their dehydroxylation as well as hydrolysis of NHx species take place. In situ DRIFTS study showed that the limiting steps are slow chemical reactions, but not a diffusion of NH3 or H2O molecules in the bulk of glasses. The concept on strained siloxane bridges formed due to dehydroxylation of two adjacent silanol groups was used for explanation of the reaction kinetics features.
CARBONYLATION OF DIMETHYL ETHER ON SOLID Rh-PROMOTED Cs-SALT OF KEGGIN 12-H3PW12O40: A SOLID-STATE NMR STUDY OF THE REACTION MECHANISM
M.V. Luzgin, M.S. Kazantsev, G.G. Volkova, W. Wang*, A.G. Stepanov (*Lanzhou University, Gansu, PR China)
J. Catal., 277(1) (2011) pp. 72-79.
The carbonylation of dimethyl ether (DME) with carbon monoxide on Rh-promoted cesium salt of 12-tungstophosphoric acid, Rh/Cs2HPW12O40 (HPA), has been studied with 13C solid-state NMR. The bi-functional character of Rh/Cs2HPW12O40 catalyst in halide-free carbonylation of DME has been directly demonstrated. The activation of the C–O bond of DME proceeds on Brønsted acid sites of HPA with the formation of the methyl group attached to the surface of HPA (methoxy species), whereas the role of rhodium consists in trapping carbon monoxide from gaseous phase and a transfer of CO to the center of DME activation, acidic OH-group of the catalyst, in the form of rhodium carbonyls. The lattice of Cs2HPW12O40 makes it possible to locate these two different active centers in close proximity to each other, e.g., on two adjacent oxygen atoms, terminal and bridging, of one Keggin anion, thus facilitating the insertion of carbon monoxide from rhodium carbonyl into the C–O bond of methoxy-group to produce the acetate group bound to the Keggin anion. The latter offers finally methyl acetate under the interaction with DME, the intermediate surface methoxy-groups being restored.
HYDROGEN H/D EXCHANGE AND ACTIVATION OF C1-n-C4 ALKANES ON Ga-MODIFIED ZEOLITE BEA STUDIED WITH 1H MAGIC ANGLE SPINNING NUCLEAR MAGNETIC RESONANCE in situ
A.A. Gabrienko, S.S. Arzumanov, A.V. Toktarev, D. Freude*, J. Haase*, A.G. Stepanov (*University of Leipzig, Leipzig, Germany)
J. Phys. Chem., 115(28) (2011) pp. 13877-13886.
Kinetics of H/D hydrogen exchange between C1-n-C4 alkanes and Bronsted acid sites (BAS) of both the pure acid-form zeolite BRA (H-BRA) and Ga-modified zeolite BRA (Ga/H-BEA) was monitored by 1H MAS NMR spectroscopy in situ at 423-563 K. Comparative analysis of the rates of the exchange for H-BRA and Ga/H-BRA zeolites reveals a remarkable increase of the rate by 1-2 orders of magnitude, decrease of activation energy, and an appearance of regioselectivity of the exchange into the methyl groups of C3-n-C4 alkanes upon modification of H-BEA zeolite with gallium. These data identify an evident promoting effect of Ga on activation of alkane C-H bonds by BAS. The effect has been rationalized by preliminary dissociative adsorption of alkanes on gallium(III) oxide species inside zeolite pores to form gallium-alkyl species, which are further involved in the exchange with neighbor BAS. Involvement of both BAS and Ga species in alkane activation accounts for earlier suggested synergistic effect (Buckles, G., et al. Catal. Lett. 1991, 11, 89) of both BAS and gallium species in alkane activation and aromatization on Ga-modified high silica zeolites.
CATALYTIC ENANTIOSELECTIVE OXIDATION OF BULKY ALKYL ARYL THIOETHERS WITH H2O2 OVER TITANIUM-SALAN CATALYSTS
K.P. Brylyakov, E.P. Talsi
Eur. J. Org. Chem., 24 (2011) pp. 4693-4698.
A simple and efficient catalytic procedure for the oxidation of bulky (preferably aryl benzyl substituted) thioethers with hydrogen peroxide in good to high yields and enantioselectivities (up to 98.5 % ee) is reported. The high optical yields are achieved in a tandem stereoconvergent enantioselective oxidation and kinetic resolution process. A reasonable balance between the sulfoxide yield and enantioselectivity could be found by varying the concentration and temperature. An improved synthesis of the titanium-salan catalysts for the preparation of a more stereoselective catalyst is reported.
NON-HEME MANGANESE COMPLEXES CATALYZED ASYMMETRIC EPOXIDATION OF OLEFINS BY PERACETIC ACID AND HYDROGEN PEROXIDE
R.V. Ottenbacher, K.P. Brylyakov, E.P. Talsi
Adv. Synth. Catal., 353(6) (2011) pp. 885-889.
Chiral non-heme aminopyridine manganese complexes catalyze the enantioselective epoxidation of olefins with peracetic acid or hydrogen peroxide with moderate to high yields and ee values up to 89% (peracetic acid, AcOOH) and 84% (hydrogen peroxide, H2O2), performing as many as 1000 turnovers.
EPR, 1H AND 2H NMR, AND REACTIVITY STUDIES OF THE IRON–OXYGEN INTERMEDIATES IN BIOINSPIRED CATALYST SYSTEMS
O.Yu. Lyakin, K.P. Brylyakov, E.P. Talsi
Inorg. Chem., 50(12) (2011) pp. 5526–5538.
Complexes [(BPMEN)FeII(CH3CN)2](ClO4)2 (1, BPMEN = N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)-1,2-diaminoethane) and [(TPA)FeII(CH3CN)2](ClO4)2(2, TPA = tris(2-pyridylmethyl)amine) are among the best nonheme iron-based catalysts for bioinspired oxidation of hydrocarbons. Using EPR and 1H and 2H NMR spectroscopy, the iron–oxygen intermediates formed in the catalyst systems 1,2/H2O2; 1,2/H2O2/CH3COOH; 1,2/CH3CO3H; 1,2/m-CPBA; 1,2/PhIO; 1,2/tBuOOH; and 1,2/tBuOOH/CH3COOH have been studied (m-CPBA is m-chloroperbenzoic acid). The following intermediates have been observed: [(L)FeIII(OOR)(S)]2+, [(L)FeIV═O(S)]2+ (L = BPMEN or TPA, R = H or tBu, S = CH3CN or H2O), and the iron–oxygen species 1c (L = BPMEN) and 2c (L = TPA). It has been shown that 1c and 2c directly react with cyclohexene to yield cyclohexene oxide, whereas [(L)FeIV═O(S)]2+ react with cyclohexene to yield mainly products of allylic oxidation. [(L)FeIII(OOR)(S)]2+ are inert in this reaction. The analysis of EPR and reactivity data shows that only those catalyst systems which display EPR spectra of 1c and 2c are able to selectively epoxidize cyclohexene, thus bearing strong evidence in favor of the key role of 1c and 2c in selective epoxidation. 1c and 2c were tentatively assigned to the oxoiron(V) intermediates.
HOMOCHIRAL POROUS METAL-ORGANIC FRAMEWORKS: A STEP TO THE FUTURE OF STEREOSELECTIVE RECOGNITION AND CATALYSIS
K.P. Brylyakov, E.P. Talsi
In “Chemical Physics Research and Developments”, Nova Science Publishers, NY, 2011, pp. 47-59.
In this commentary, the authors present an overview of known homochiral metal-organic materials capable of stereoselective recognition, sorption and separation of guest molecules and those promoting asymmetric catalytic processes inside the chiral pores.
ELECTRICAL CONDUCTIVITY OF MAGNESIUM OXIDE AS A CATALYST FOR RADICAL CHAIN HYDROCARBON PYROLYSIS REACTIONS
N.A. Vasilieva, N.F. Uvarov* (*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia)
Kinet. Catal., 52(1) (2011) pp. 98-103.
The electrical conductivity of polycrystalline MgO between 350 and 750°C is determined by the transport of surface electronic and hole defects and depends on the applied voltage. Near 620°C at low applied voltages, the conductivity decreases by 1–2 orders of magnitude in a narrow temperature range (ΔT = 75°C), and this is accompanied by a change of the sign of the surface charge carriers. The “ignition” of the catalytic activity of magnesium oxide in free radical generation in radical chain hydrocarbon pyrolysis is observed in the same temperature range. It is assumed that the change of the sign of the charge carriers is due to the existence of an isoelectric temperature Ti and that, at T > Ti, OO· defects come out to the magnesium oxide surface.
AMMONIA SYNTHESIS FROM DINITROGEN AND DIHYDROGEN OVER THE CATALYSTS BASED ON SUPPORTED MONONUCLEAR POTASSIUM CARBONYL RUTHENATE. PROMOTING EFFECT OF ALKYLLITHIUM COMPOUNDS
S.M. Yunusov*, E.S. Kalyuzhnaya*, B.L. Moroz, A.S. Ivanova, V.B. Shur* (*Nesmeyanov Institute of Organoelement Compounds, Moscow, Russia)
Russ. Chem. Bull., 60(9) (2011) pp. 1842-1847.
New catalysts for the ammonia synthesis from dinitrogen and dihydrogen based on supported mononuclear potassium carbonyl ruthenate K2Ru[(CO)4] as a precursor of catalytically active particles have been developed. Magnesium oxide and graphite-like active carbon Sibunit were used as supports, while aliphatic organolithium compounds (BunLi and ButLi) were employed as electron promoters in these catalysts. The systems with MgO as a support are the most efficient. The introduction of RLi into these systems allows one to considerably increase the ammonia synthesis rate. When using carbon Sibunit, the promoting effect of organolithium compounds is much weaker but the activity of such catalysts can be essentially increased by the introduction of an additional electron promoter, viz., metallic potassium, into the system. All the catalysts tested are active in the ammonia synthesis at atmospheric pressure and temperatures ≥250°C.
X-RAY DIFFRACTION STRUCTURE DIAGNOSTICS OF NANOMATERIALS
Russ. Chem. Rev., 80(4) (2011) pp. 293-312.
The review concerns the development and applications of the X-ray diffraction method of the radial electron density distribution based on the integral analysis of X-ray diffraction in studies of nanomaterials, in particular, oxide supports for catalysts. The method provides information on the interatomic distances and coordination numbers in the structure and allows one to detect and estimate the size of nanostructures (phases) less than 3 nm in size, which cannot be detected by conventional powder X-ray diffraction analysis. The method is sensitive to the changes in the local structure measuring 1-3 unit cells; therefore, it is successfully used to identify various defects in nanoobjects of any chemical composition. The bibliography includes 124 references.
STUDY OF PHASE COMPOSITION OF NANOMATERIALS
Nanoeng., 5 (2011) pp. 26-32.
The possibilities of X-ray techniques to determine the phase composition of typical nanomaterials and nanostructures - catalysts and carriers for them – are considered. For supported catalysts it is shown that besides phases characteristic for support and active component, there are always present the phase formed as a result of interaction between support and active component. Metastable phases are identified for oxide systems. Examples of investigation of defective nanostructures are considered.
POSSIBILITIES OF X-RAY DIFFRACTION STRUCTURE DIAGNOSTICS OF NANOMATERIALS
Nanoeng., 4 (2011) pp. 3-21.
In this work the data on the development and use of radial electron distribution function or pair distribution function method based on integral analysis of X-ray scattering curve are presented. The method gives information about interatomic distances and coordination numbers and it is used for detection of nanospecies (phases) with sizes lower than 3 nm and estimation of their sizes. Such highly dispersed species are not detected by conventional X-ray phase analysis based on consideration of interplanar spacings. The method is sensitive to changes in local structure (short range arrangement of atoms in the range of 1...3 elementary cells), so it is used successfully for determination of defects in the nanomaterials.
A STUDY OF THE LOCAL STRUCTURE OF ALUMINAS OBTAINED BY DIFFERENT METHODS
E.M. Moroz, K.I. Shefer, D.A. Zyuzin, A.N. Shmakov
J. Struct. Chem., 52(2) (2011) pp. 326-329.
The local structure of aluminas obtained from hydroxides (pseudo-boehmites) synthesized by different methods is studied using the radial density distribution function. The occupancy of the cation sites of different types (tetrahedral and octahedral, spinel and non-spinel) in the structure of the studied oxides is analyzed.
Pt-IMPLANTED INTERMETALLIDES AS THE CATALYSTS FOR CH4-CO2 REFORMING
L.A. Arkatova*, O.V. Pakhnutov*, A.N. Shmakov, Yu.S. Naiborodenko**, N.G. Kasatsky*** (*Tomsk V.V. Kuibyshev State University, Tomsk, Russia; **Tomsk Scientific Center, Tomsk, Russia)
Catal. Today, 171(1) (2011) pp. 156-167.
A new type of catalytic system on the base of Ni3Al intermetallic compound was proposed for CO2 reforming of methane. Several catalysts were prepared by self-propagating high temperature synthesis and characterized by XRD (in situ and ex situ), DTA-TG, SEM + EDS, HRTEM + EDS and XPS. Ion implantation was used as a method of catalyst surface modification. Activity testing has been performed in the fixed bed reactor at the temperatures of 600–900°C under atmospheric pressure and the reactant molar ratio of 1. The structure and morphology of different types of carbon deposits obtained on the surface of unmodified Ni3Al were investigated. The results indicated that the addition of a low amount (less than 0.1 wt%) of Pt to the Ni3Al intermetallide leads to a decrease in carbon deposition and Pt-implanted catalysts were stable for a long period of time. The evidence suggests that the differences in the stabilities may be due to the following reasons: (1) Pt prevents Ni phase sintering by avoiding particle coalescence, which is the main sintering process under severe CH4–CO2 reforming conditions, (2) Pt hinders deactivating carbon formation by limiting bulk nickel carbide and therefore carbon filament formation, which may lead to reactor plugging and/or particle fragmentation, and by suppressing encapsulating carbon formation which limits access of reactant to the active nickel phase.
ACTIVITY OF COPPER–CERIUM–ZIRCONIUM CATALYSTS IN OXIDATION OF HYDROGEN
A.V. Gural’skii*, G.R. Kosmambetova*, E.M. Moroz, V.I. Gritsenko*, P.E. Strizhak*
(*Pisarzhevskii Institute of Physical Chemistry, Kiev, Ukraine)
Theor. Exp. Chem., 47(4) (2011) pp. 251-256.
The authors have studied the catalytic properties in oxidation of hydrogen for copper–cerium oxide systems deposited on supports obtained by calcination of yttrium-stabilized zirconium dioxide at 300–100°C. The authors have shown that the catalytic activity of the samples obtained depends on the specific surface area of the original supports and the amount of reduced copper within the composition of the catalyst. In samples whose support has high specific surface area, the content of reduced metallic copper is greater and the catalytic activity is higher.
LOW TEMPERATURE HYDROGEN PURIFICATION FROM CO FOR FUEL CELL APPLICATION OVER COPPER-CERIA CATALYSTS SUPPORTED ON DIFFERENT OXIDES
G.R. Kosmambetova*, E.M. Moroz, A.V. Guralsky*, V.P. Pakharukova, A.I. Boronin, T.S. Ivashchenko*, V.I. Gritsenko*, P.E. Strizhak* (*Pisarzhevskii Institute of Physical
Chemistry, Kiev, Ukraine)
Int. J. Hydrogen Energy, 36(1) (2011) pp. 1271-1275.
The CuO–CeO2–MeOx (Me = Zr, Ti, Mn, Al; x = 1.5–2) solids were tested in the preferential CO oxidation reaction in hydrogen-rich gas mixtures (PROX). The authors study an effect of a support (MeOx) on the CO conversion and selectivity in the PROX reaction showing that monoclinic zirconia (m-zirconia) with low surface area is the most effective support. The optimal catalyst composition was determined by varying copper and ceria loadings over m-zirconia. XRD and XPS studies indicate that a good catalytic performance of m-zirconia supported copper–ceria catalysts may be attributed to the presence of dispersed Cu-containing species that interact with CeO2 and ZrO2.
EFFECTS OF SPATIAL ORDERING OF QUANTUM DOT ARRAYS FROM SMALL-ANGLE X-RAY DIFFRACTION DATA UNDER VARIATION OF GROWTH PARAMETERS
L.M. Plyasova, LYu. Molina, N.P. Stepina*, A.F. Zinov’eva*, A.V. Dvurechenskii* (*Institute of Semiconductor Physics, Novosibirsk, Russia)
J. Surf. Invest. - X-Ray Synchrotron Neutron Techn., 5(1) (2011) pp. 120-125.
The small angle X-ray diffraction method is applied to the system of germanium quantum dots in the silicon matrix prepared by molecular-beam epitaxy in self-organization mode using the Stranski-Krastanov technique. Depending on the growth mode, the specific distances between Ge quantum dots and deviations from their correlated distribution are determined. The results are in agreement with the scanning tunneling microscopy data.
ELECTRODEPOSITED OXOTUNGSTATE FILMS: TOWARDS THE MOLECULAR NATURE OF RECHARGING PROCESSES
V.K. Laurinavichute*, S.Yu. Vassiliev*, A.A. Khokhlov*, L.M. Plyasova, LYu. Molina, G.A. Tsirlina* (*Moscow Lomonosov State University, Moscow, Russia)
Electrochim. Acta, 56(10) (2011) pp. 3530-3536.
In situ Raman spectroscopy is applied to supplement voltammetric, spectroelectrochemical, and XRD data on redox transformations of electrodeposited oxotungstate films. These films undergo electrochromic transition at rather positive potentials, as compared to usual sputtered tungsten oxides. The depth of electroreduction for the films conditioned in acidic solutions under open circuit is about 0.11 e" per W atom. Coloration of the films correlates with the decrease of Raman band, corresponding to the terminal W(VI)=O vibration in the hydrated phase of highly defective tungstic acid (hydrated tungsten oxide). The data allow to state the absence of oxotungstate octahedra rearrangement in the course of reduction at positive RHE potentials, and to assume that slightly deeper reduction up to 0.15 W(V)/[W(V) + W(VI)] ratio is possible at more negative potentials. The authors also demonstrate that the gas phase reduction is less reversible as compared to electrochemical reduction in solution. The most possible nature of films degradation in the gas phase is their partial dehydration in the course of reduction.
HIGH-TEMPERATURE XRD INVESTIGATION OF SPINEL Mn1.5Al1.5O4 DECOMPOSITION
O.A. Bulavchenko, S.V. Tsybulya, E.Yu. Gerasimov, S.V. Cherepanova, T.N. Afonasenko*, P.G. Tsyrulnikov* (*Institute of Hydrocarbons Processing, Omsk, Russia)
Z. Kristallogr. Proc., 1 (2011) pp. 325-330.
This article describes a study of behaviour of cubic Mn1.5Al1.5O4 spinel during heating and cooling under air. High-temperature XRD and TEM were used to investigate structure transformations and sample microstructure. XRD data show spinel decomposition during cooling and heating under air at 500-700°C. The products of decomposition consist of nanocrystalline tetragonal phase (with particle size of 20 nm) and cubic spinel (50 nm). Cubic spinel composition changes by various ways on the initial step during the heating and cooling. Thus, the structure mechanisms of decomposition are different. But the final decomposition products are the same.
PRODUCING OF Cu/ZrO2 COMPOSITES BY COMBINING MECHANICAL ACTIVATION AND SELF-PROPAGATING HIGH-TEMPERATURE SYNTHESIS
T.F. Grigor’eva*, A.I. Letsko**, T.L. Talako**, S.V. Tsybulya, I.A. Vorsina*, A.P. Barinova*, A.F. Il’yushchenko**, N.Z. Lyakhov* (*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia; **Institute of Powder Metallurgy NAS Belarus)
Combust. Explosion Shock Waves, 47(2) (2011) pp. 174-178.
The possibility of producing Cu/ZrO2 composites by combining mechanical activation and self-propagating high-temperature synthesis (SHS) is studied using X-ray diffraction and electron microscopy. It is shown that Cu/ZrO2 composites are formed in SHS using CuO/Cu/Zr mechanocomposite as a precursor.
INFLUENCE OF Al IONS ON THE REDUCTION OF Co3xAlx04: in situ XRD INVESTIGATION
S.V. Cherepanova, O.A. Bulavchenko, I.I. Simentsova, E.Yu. Gerasimov, A.A. Khassin
Z. Kristallogr. Proc, 1 (2011) pp. 331-336.
The addition of small amounts of Al ions to nanocrystalline Co3O4 leads to considerable changes in its reduction. In situ XRD and TPR show that Al ions affect the extent of cobalt reduction achieved in a hydrogen flow. Co3O4 is fully reduced to metallic cobalt at a temperature of ca. 200°C. As for Al-modified samples Co3-xAlxO4 (x = 0.05, 0.1, 0.2), they contain CoO even after reduction at 350°C. The higher is the Al content; the lower is the Co/CoO ratio. At 350°C, metallic particles in all cases consist of platelet domains having the hcp and fcc structure. In the case of metallic cobalt reduced from Co3O4, the fcc domains are twice thinner as compared to hcp ones, their average thicknesses being ca. 0.9 nm and 1.8 nm, respectively. In metallic cobalt reduced from Co3-xAl x O4 (x = 0.05, 0.1, 0.2), the fcc and hcp domains have almost equal average thicknesses of ca. 1.4 nm.
ANIONIC COMPOSITION OF PRECURSORS OF THE Co/Al203 CATALYSTS FOR THE FISCHER-TROPSCH SYNTHESIS
LI. Simentsova, A.A. Khassin, G.A. Filonenko, G.K. Chermashentseva, O.A. Bulavchenko, S.V. Cherepanova, T.M. Yurieva
Russ. Chem. Bull., 60(9) (2011) pp. 1827-1834.
Cobalt and aluminum hydroxo compounds with the hydrotalcite-type structure containing nitrate, carbonate, and hydroxyl groups are formed due to the deposition by precipitation of cobalt cations from a nitrate solution on 5- and y-Al2O3 under the conditions of urea hydrolysis. The influence of the method of preparation on the anionic composition of the hydroxo compounds (precursors of the Co-Al catalyst) was studied. A correlation between the anionic composition of the precursor compound and the catalytic properties of the catalysts in the Fischer-Tropsch synthesis was established.
SYNTHESIS, CRYSTAL STRUCTURE AND THERMAL PROPERTIES OF [Co(NH3)5Cl]MoO4(M = Mo, W)
E.A. Shusharina*, S.P. Khranenko*, P.E. Plusnin*, T.Yu. Kardash, S.A. Gromilov*
(*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
J. Struct. Chem., 52(5) (2011) pp. 918-923.
Crystal structures of [Co(NH3)5Cl]MoO4 and [Co(NH3)5Cl]WO4 complex salts are determined by single crystal X-ray diffraction. It is demonstrated for both salts that within the temperature range T = -123-20°C there is a negative thermal expansion (about 0.26%) towards the с axis of the orthorhombic unit cell (Pnma space group). Thermal properties of the salts are investigated. The phase composition of the products obtained on heating the salts in different gas atmospheres is studied.
CRYSTAL STRUCTURE AND THERMAL PROPERTIES OF [AuCen^hlCu^O^bSHjO
E.V. Makotchenko*, E.A. Bykova*, E.Yu. Semitut*, Yu.V. Shubin*, P.V. Snytnikov, P.E. Plyusnin* (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
J. Struct. Chem., 52(5) (2011) pp. 924-929.
The crystal structure of a double complex salt of the composition [Au(en)2]2[Cu(C2O4)2]3-8H2O (en = ethylenediamine) at 150 K is determined by single crystal X-ray diffraction. The crystal data for C20H48Au2Cu3N8O32 are: a = 9.1761(3) Å, b = 16.9749(6) Å, c = 13.4475(5) Å, (3 = 104.333(1)°, V = 2029.43(12) Å3, P21/c space group, Z = 2, dx = 2.450 g/cm3. It is demonstrated that the thermal decomposition of the double complex salt in a helium or hydrogen atmosphere affords the solid solution Au0.4Cu0.6.
MICROPOROUS SENSOR: GAS SORPTION, GUEST EXCHANGE AND GUEST-DEPENDANT LUMINESCENCE OF METAL-ORGANIC FRAMEWORK
S.A. Sapchenko*, D.G. Samsonenko*, D.N. Dybtsev*,**, M.S. Melgunov, V.P. Fedin* (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Division of the Advanced Materials Science, POSTECH, Hyojadong, Pohang, Republic of Korea)
Dalton Trans., 40(10) (2011) pp. 2196-2203.
Zn(II)-containing metal–organic framework (MOF) [Zn4(dmf)(ur)2(ndc)4] (ndc2- = 2,6-naphtalenedicarboxylate, ur = urotropin, dmf = N,N′-dimethylformamide) was synthesized and characterized by X-ray crystallography and gas sorption analysis. Host MOF retains its crystallinity after guest removal and exchange. Single-crystal to single-crystal formation of different host–guest systems with benzene and ferrocene was investigated. Interesting guest-depended luminescence properties of the porous host framework were observed.
XPS FOR in situ STUDY OF THE MECHANISMS OF HETEROGENEOUS CATALYTIC REACTIONS
V.V. Kaichev, I.P. Prosvirin, V.I. Bukhtiyarov
J. Struct. Chem., 52(suppl.) (2011) pp. 90-101.
The possibility to use X-ray photoelectron spectroscopy (XPS) for in situ studies of the mechanisms of heterogeneous catalytic reactions over the pressure range from ultrahigh vacuum to 100 mbar is considered. The application of this method to investigation of CO adsorption and hydrogenation as well as kinetics and mechanism of methanol transformation on the palladium surface at pressures of 10-6 mbar to 0.1 mbar is reported.
A STUDY OF THE STRUCTURE OF (HfO2)x(Al2O3)1-x/Si FILMS BY X-RAY PHOTOELECTRON SPECTROSCOPY
V.V. Kaichev, Yu.V. Dubinin, T.P. Smirnova*, M.S. Lebedev* (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
J. Struct. Chem., 52(3) (2011) pp. 480-487.
By X-ray photoelectron spectroscopy (XPS), using the technique of layer-by-layer analysis, the films of (HfO2)x(Al2O3)1-x solid solutions synthesized by chemical vapor deposition are studied. The possibility to determine the structure of solid binary solutions based on the analysis of the XPS spectra is demonstrated.
X-RAY PHOTOELECTRON SPECTROSCOPY DEPTH PROFILING OF La2O3/Si THIN FILMS DEPOSITED BY REACTIVE MAGNETRON SPUTTERING
C.V. Ramana*, R.S. Vemuri*, V.V. Kaichev, V.A. Kochubey**, A.A. Saraev, V.V. Atuchin**
(*University of Texas at El Paso, El Paso, Texas, USA; **Institute of Semiconductor Physics, Novosibirsk, Russia)
ACS Appl. Mater. Interfaces, 3(11) (2011) pp. 4370-4373.
The La2O3/Si thin films have been deposited by reactive DC magnetron sputtering. Amorphous state of La2O3 layer has been shown by RHEED observation. Top surface chemistry of the a-La2O3 has been evaluated with layer-by-layer depth profiling by ion bombardment and XPS measurements. It was found by core level spectroscopy that the top surface of the a-La2O3 film consists of hydrocarbon admixture, lanthanum carbonate, and hydroxides that formed as a result of contact with air atmosphere. Thickness of this top surface modified layer is below 1 nm for a contact time of ~ 1.5 h with air at normal conditions.
ELECTRONIC STRUCTURE OF δ-Ta2O5 WITH OXYGEN VACANCY:I>ab initio CALCULATIONS AND COMPARISON WITH EXPERIMENT
M.V. Ivanov*, T.V. Perevalov*, V.S. Aliev*, V.A. Gritsenko*, V.V. Kaichev (*Rzhanov Institute of Semiconductor Physics, Novosibirsk, Russia)
J. Appl. Phys., 110(2) (2011) pp. 024115 (5 pp).
Electronic structure of oxygen vacancies in Ta2O5 have been studied theoretically by first-principles calculations and experimentally by X-ray photoelectron spectroscopy. Calculations of δ-Ta2O5 were performed using density functional theory within gradient-corrected approximation with the +U approach. Results indicate that the oxygen vacancy causes a defect level in the energy gap at 1.2 eV above the top of the valence band. To produce oxygen vacancies, amorphous films of Ta2O5 were bombarded with Ar+ ions. XPS results indicate that the Ar-ion bombardment leads to the generation of the oxygen vacancies in Ta2O5 that characterize the peak at 2 eV above the valence band. The calculated spectrum of crystalline δ-Ta2O5 demonstrates qualitative correspondence with the XPS spectrum of the amorphous Ta2O5 film after Ar-ion bombardment.
Ab initio SIMULATION OF THE ELECTRONIC STRUCTURE OF δ-Ta2O5 WITH OXYGEN VACANCY AND COMPARISON WITH EXPERIMENT
M.V. Ivanov*, T.V. Perevalov*, V.Sh. Aliev*, V.A. Gritsenko*, V.V. Kaichev (*Rzhanov Institute of Semiconductor Physics, Novosibirsk, Russia)
J. Exp. Theor. Phys., 112(6) (2011) pp. 1035-1041.
The electronic structure of a Ta2O5 insulator with oxygen vacancies is studied theoretically and experimentally. The ab initio calculations of δ-Ta2O5 are performed in terms of density functional theory using the generalized gradient (GGA) and GGA + U approximations. The electronic structure of Ta2O5 is experimentally studied by X-ray photoelectron spectroscopy (XPS). To study oxygen vacancies, an amorphous Ta2O5 film is irradiated by argon ions. The calculated XPS spectra of the valence band of δ-Ta2O5 agree satisfactorily with the corresponding experimental spectra of the amorphous films. The oxygen vacancy in δ-Ta2O5 is found to be a trap for holes and electrons. The minimum and maximum effective masses of electrons and holes in δ-Ta2O5 are calculated.
NEW TECHNIQUE FOR HETEROGENEOUS VAPOR-PHASE SYNTHESIS OF NANOSTRUCTURED METAL LAYERS FROM LOW-DIMENSIONAL VOLATILE METAL COMPLEXES
A.M. Badalyan*, L.F. Bakhturova*, V.V. Kaichev, O.V. Polyakov*, O.P. Pchelyakov**, G.I. Smirnov** (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Institute of Semiconductor Physics, Novosibirsk, Russia)
Tech. Phys., 56(9) (2011) pp. 1333-1338.
A new technique for depositing thin nanostructured layers on semiconductor and insulating substrates that is based on heterogeneous gas-phase synthesis from low-dimensional volatile metal complexes is suggested and tried out. Thin nanostructured copper layers are deposited on silicon and quartz substrates from low-dimensional formate complexes using a combined synthesis-mass transport process. It is found that copper in layers thus deposited is largely in a metal state (Cu0) and has the form of closely packed nanograins with a characteristic structure.
FROM ‘CORE–SHELL’ TO COMPOSITE MIXED CATHODE MATERIALS FOR RECHARGEABLE LITHIUM BATTERIES BY MECHANOCHEMICAL PROCESS
N.V. Kosova*, E.T. Devyatkina*, V.V. Kaichev, A.B. Slobodyuk** (*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia; **Institute of Chemistry, Vladivostok, Russia)
Solid State Ionics, 192(1) (2011) pp. 284-288.
Solid state mechanical activation method was applied for surface modification of LiMn2O4 by Li–M–O (M = Co, Co+Ni) and for preparation of composite mixed LiMn2O4/LiCoO2 cathode materials. Pristine LiMn2O4 was ground with correspondent precursors (for coating) or with LiCoO2 (for composites) in high-energy planetary mills and then heat treated at different temperatures. As prepared materials were studied by XRD, 7Li MAS NMR spectroscopy, XPS, SEM and electrochemical cycling. It has been shown that both ‘core–shell’ and composite materials prepared by mechanochemical process are characterized by superior electrochemical performance due to smaller particles and chemical modification of LiMn2O4.
XPS STUDY OF PHARMACOLOGICAL SUBSTANCES MECHANOCHEMICALLY IMMOBILIZED ON THE SURFACE OF ALUMINA
A.I. Nizovskii, A.V. Kalinkin, T.P. Shakhtshneider*, M.A. Dyakonova*, S.A. Myz*, E.V. Boldyreva*, R. Kumar** (*Institute of Solid-State Chemistry and Mechanochemistry, Novosibirsk, Russia; **National Metallurgical Laboratory, Jamshedpur, Bihar, India)
J. Struct. Chem., 52(suppl.) (2011) pp. 137-144.
Piroxicam and meloxicam nanocomposites with alumina were synthesized by mechanochemical treatment of medicinal substances mixed with the oxide. X-ray photoelectron spectroscopy demonstrated that interaction of the components during mechanicalactivation proceeds via binding the amide and sulfate groups in the molecules of medicinal substances with the active sites of alumina surface. XPS studies confirmed the formation of “core-shell” composites with the shell represented by medicinal substances distributed over the support surface.
MECHANOCHEMICAL PREPARATION OF ORGANIC-INORGANIC HYBRID MATERIALS OF DRUGS WITH INORGANIC OXIDES
T.P. Shakhtshneider*, S.A. Myz*, M.A. Dyakonova*, V.V. Boldyrev*, E.V. Boldyreva*, A.I. Nizovskii, A.V. Kalinkin, R. Kumar** (*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia; **National
Metallurgical Laboratory, Jamshedpur, Bihar, India)
Acta Phys. Pol., A, 120(2) (2011) pp. 272-278.
The nanocomposites of piroxicam and meloxicam with alumina were obtained by ball-milling as a result of distribution of the drugs at the surface of oxide with formation of the stable composites. The observed changes in the IR spectra of the ball-milled mixtures suggested the interaction of the drugs with the alumina active surface sites. The functional groups in molecules of piroxicam and meloxicam involved into formation of bonds between the drugs and the surface of the oxide were determined, they are amide, sulfate, enol groups, and pyridyl/thiazolyl nitrogen atoms. It appears that the formation of the new bonds at the contacts of particles in the composite leads to the stabilization of the drugs in metastable state inhibiting their transformation into initial crystalline form.
USE OF THE DIFFERENTIAL CHARGING EFFECT IN XPS TO DETERMINE THE NATURE OF SURFACE COMPOUNDS RESULTING FROM THE INTERACTION OF A Pt/(BaCO3 + CeO2) MODEL CATALYST WITH SOx
M.Yu. Smirnov, A.V. Kalinkin, A.A. Dubkov*, E.I. Vovk, A.M. Sorokin, A.I. Nizovskii, B. Carberry*, V.I. Bukhtiyarov (*Ford Forschungszentrum, Aachen, Germany)
Kinet. Catal., 52(4) (2011) pp. 595-604.
Changes in the chemical composition of the surface of a Pt/(BaCO3 + CeO2) model NOx storage-reduction catalyst upon its interaction with SOx (SO2 (260 Pa) + O2 (2600 Pa) + H2O (525 Pa)) followed by regeneration in a mixture of CO (2100 Pa) with H2O (525 Pa) were studied by X-ray photoelectron spectroscopy (XPS). Model catalyst samples were prepared as a thin film (about several hundreds of angstrom units in thickness) on the surface of tantalum foil coated with a layer of aluminum oxide (∼100 Å). It was found that the Pt/BaCO3 and Pt/CeO2 catalyst constituents acquired different surface charges (differential charging) in the course of photoelectron emission; because of this, it was possible to determine the nature of surface compounds formed as a result of the interaction of the catalyst with a reaction atmosphere. It was found that barium carbonate was converted into barium sulfate as a result of reaction with SOx on the surface of BaCO3 at 150°C. As the treatment temperature in SOx was increased to 300°C, the formation of sulfate on the surface of CeO2 was observed. The sulfatization of CeO2 was accompanied by the reduction of Ce(IV) to Ce(III). The regeneration reaction of the catalyst treated in SOx at 300°C resulted in the consecutive decomposition of cerium(III) sulfate at ≤500°C and then barium sulfate at 600–700°C. Upon the decomposition of BaSO4, a portion of sulfur was converted into a sulfide state, probably, because of the formation of BaS.
SPECTROSCOPIC ELLIPSOMETRY AND X-RAY PHOTOELECTRON SPECTROSCOPY OF La2O3 THIN FILMS DEPOSITED BY REACTIVE MAGNETRON SPUTTERING
V.V. Atuchin*, A.V. Kalinkin, V.A. Kochubey*, V.N. Kruchinin*, R.S. Vemuri**, C.V. Ramana** (*Institute of Semiconductor Physics, Novosibirsk, Russia; **University of Texas at El Paso, El Paso, Texas, USA)
J. Vac. Sci. Technol., A, 29(2) (2011) 021004 (5 pp.).
Lanthanum oxide (La2O3) films were grown by the reactive dc magnetron sputtering and studied their structural, chemical and optical parameters. La2O3 films were deposited onto Si substrates by sputtering La-metal in a reactive gas (Ar+O2) mixture at a substrate temperature of 200°C. Reflection high-energy electron diffraction measurements confirm the amorphous state of La2O3 films. Chemical analysis of the top-surface layers evaluated with X-ray photoelectron spectroscopy indicates the presence of a layer modified by hydroxylation due to interaction with atmosphere. Optical parameters of α-La2O3 were determined with spectroscopic ellipsometry (SE). There is no optical absorption over spectral range λ = 250–1100 nm. Dispersion of refractive index of α-La2O3 was defined by fitting of SE parameters over λ = 250–1100 nm.
A DIRECT EVIDENCE FOR THE INSTABILITY AND DEACTIVATION OF MIXED-OXIDE SYSTEMS: INFLUENCE OF SURFACE SEGREGATION AND SUBSURFACE DIFFUSION
E. Emmez*, E.I. Vovk, V.I. Bukhtiyarov, E. Ozensoy* (*Bilkent University, Bilkent, Ankara,Turkey)
J. Phys. Chem. C, 115(45) (2011) pp. 22438-22443.
In the current contribution, a direct demonstration is provided of the thermally induced surface structural transformations of an alkaline-earth oxide/transition metal oxide interface that is detrimental to the essential catalytic functionality of such mixed-oxide systems toward particular reactants. The BaOx/TiO2/Pt(111) surface was chosen as a model interfacial system where the enrichment of the surface elemental composition with Ti atoms and the facile diffusion of Ba atoms into the underlying TiO2 matrix within 523–873 K leads to the formation of perovskite type surface species (BaTiO3/Ba2TiO4/BaxTiyOz). At elevated temperatures (T > 973 K), excessive surface segregation of Ti atoms results in an exclusively TiO2/TiOx-terminated surface which is almost free of Ba species. Although the freshly prepared BaOx/TiO2/Pt(111) surface can strongly adsorb ubiquitous catalytic adsorbates such as NO2 and CO2, a thermally deactivated surface at T > 973 K practically loses all of its NO2/CO2 adsorption capacity due to the deficiency of surface BaOx domains.
ROLE OF THE EXPOSED Pt ACTIVE SITES AND BaO2 FORMATION IN NOx STORAGE REDUCTION SYSTEMS: A MODEL CATALYST STUDY ON BaOx/Pt(111)
E.I. Vovk, E. Emmez*, M. Erbudak**, V.I. Bukhtiyarov, E. Ozensoy* (*Bilkent University, Bilkent, Ankara, Turkey; **Laboratorium für Festkörperphysik, ETH Zurich, Zurich, Switzerland)
J. Phys. Chem. C, 115(49) (2011) pp. 24256-24266.
BaOx (0.5 MLE - 10 MLE)/Pt(111) (MLE: monolayer equivalent) surfaces were synthesized as model NOx storage reduction (NSR) catalysts. Chemical structure, surface morphology, and the nature of the adsorbed species on BaOx/Pt(111) surfaces were studied via X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD), and low-energy electron diffraction (LEED). For θBaOx < 1 MLE, (2 × 2) or (1 × 2) ordered overlayer structures were observed on Pt(111), whereas BaO(110) surface termination was detected for θBaOx = 1.5 MLE. Thicker films (θBaOx ≥ 2.5 MLE) were found to be amorphous. Extensive NO2 adsorption on BaOx(10 MLE)/Pt(111) yields predominantly nitrate species that decompose at higher temperatures through the formation of nitrites. Nitrate decomposition occurs on BaOx(10 MLE)/Pt(111) in two successive steps: NO(g) evolution and BaO2 formation at 650 K and NO(g) + O2(g) evolution at 700 K. O2(g) treatment of the BaOx(10 MLE)/Pt(111) surface at 873 K facilitates the BaO2 formation and results in the agglomeration of BaOx domains leading to the generation of exposed Pt(111) surface sites. BaO2 formed on BaOx(10 MLE)/Pt(111) is stable even after annealing at 1073 K, whereas on thinner films (θBaOx = 2.5 MLE), BaO2 partially decomposes into BaO, indicating that small BaO2 clusters in close proximity of the exposed Pt(111) sites are prone to decomposition. Nitrate decomposition temperature decreases monotonically from 550 to 375 K with decreasing BaOx coverage within θBaOx = 0.5 to 1.0 MLE. Nitrate decomposition occurs at a rather constant temperature range of 650-700 K for thicker BaOx overlayers (2.5 MLE < θBaOx < 10 MLE). These two distinctly characteristic BaOx-coverage-dependent nitrate decomposition regimes are in very good agreement with the observation of the so-called “surface” and “bulk” barium nitrates previously reported for realistic NSR catalysts, clearly demonstrating the strong dependence of the nitrate thermal stability on the NOx storage domain size.
X-RAY PHOTOELECTRON INVESTIGATION OF CHARGE DISTRIBUTION IN COPPER(II) PHTHALOCYANINE COMPLEXES
R.V. Gulyaev, N.A. Kryuchkova*, L.N. Mazalov*, A.I. Boronin, T.V. Basova*, V.A. Plyashkevich*
(*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
J. Surf. Invest. -
X-Ray Synchrotron Neutron Techn.,
5(1) (2011) pp. 48-56.
The charged states of atoms in unsubstituted copper(II) phthalocyanine (CuPcH16) and hexade-cafluorinated copper(II) phthalocyanine (CuPcF16) complexes and in thin films of them deposited on silicon substrates by vacuum thermal evaporation are investigated by X-ray photoelectron spectroscopy (XPS). The C(1s), N(1s), Cu(2p) core level energies and the charged states of atoms in the studied complexes are calculated using the DFT method. The performed experimental study and theoretical
calculations show that the introduction of electron acceptor substituents into benzene rings mostly affects the atoms of benzene rings and insignificantly affects the charge state of nitrogen atoms in the pyrrole ring.
MICELLAR SYNTHESIS AND CHARACTERIZATION OF ULTRAFINE SILVER POWDERS
M.G. Demidova*, A.I. Bulavchenko*, T.Yu. Podlipskaya*, A.I. Boronin, L.S. Kibis, V.I. Zaikovsky (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
Russ. J. Inorg. Chem., 56(8) (2011) pp. 1199-1207.
Methods for the synthesis and coagulation of ultrafine silver powders in the water-Triton N-42-decane inverted-micellar system were developed. Varying AgNO3 concentration (1–5 mol/L), the type of reducing agent (hydrazine or potassium borohydride), and the coagulation method (spontaneous or induced by acetone or water addition) allowed to select the parameters that provide powders containing about 98% silver and having particle sizes of 15–80 nm. The authors propose methodology for characterizing ultrafine silver powders comprising the determination of the total and surface composition and the charge state of impurities using atomic absorption spectroscopy (AAS), atomic emission spectroscopy (AES), microanalysis, FTIR spectroscopy, and X-ray photoelectron spectroscopy. The impurity composition of the nanomaterial is found to depend on the type of reducing agent, the synthesis parameters, and coagulation conditions.
XES AND QUANTUM CHEMICAL INVESTIGATION OF THE ELECTRONIC STRUCTURE OF PHTHALOCYANINE COMPLEXES MPCH16 AND MPCF16 WITH M = Cu, Co
G.I. Semushkina*, L.N. Mazalov*, N.A. Kryuchkova*, A.I. Boronin, R.V. Gulyaev, T.V. Basova*, V.A. Plyashkevich* (*Nikolaev Institute of Inorganic Chmestry, Novosibirsk, Russia)
J. Struct. Chem., 52(suppl.) (2011) pp. 21-35.
The X-ray spectroscopy and X-ray electron study of the electronic structure of unsubstituted phthalocyanines MPcH16 and hexadecafluorophthalocyanines MPcF16 with M = Cu, Co is reported. Quantum-chemicalalculation of the electronic structure of these compounds was performed. The calculation was used to analyze the metal-ligand electronic interaction in the complexes. The theoretically calculated energy position and composition of the highest occupied molecular orbitals were compared with experimental data obtained from X-ray fluorescence spectra.
MOBILITY OF SOLID TERT-BUTYL ALCOHOL STUDIED BY DEUTERIUM NMR
A.M. Nishchenko, D.I. Kolokolov, A.G. Stepanov
J. Phys. Chem. A, 115(26) (2011) pp. 7428-7436.
The molecular mobility of solid deuterated tert-butyl alcohol (TBA) has been studied over a broad temperature range (103-283 K) by means of solid-state 2H NMR spectroscopy, including both line shape and anisotropy of spin—lattice relaxation analyses. It has been found that, while the hydroxyl group of the TBA molecule is immobile on the 2H NMR time scale (τC > 10―5 s), its butyl group is highly mobile. The mobility is represented by the rotation of the methyl [CD3] groups about their 3-fold axes (C3 rotational axis) and the rotation of the entire butyl [(CD3)3-C] fragment about its 3-fold axis (C3' rotational axis). Numerical simulations of spectra line shapes reveal that the methyl groups and the butyl fragment exhibit three-site jump rotations about their symmetry axes C3 and C3' in the temperature range of 103-133 K, with the activation energies and preexponential factors E1 = 21 ± 2 kJ/mol, f01 = (2.6 ± 0.5) x 1012 s―1 and E2 = 16 ± 2 kJ/mol, k02 = (1 ± 0.2) x 1012 s―1, respectively. Analysis of the anisotropy of spin―lattice relaxation has demonstrated that the reorientation mechanism of the butyl fragment changes to a free diffusion rotational mechanism above 173 K, while the rotational mechanism of the methyl groups remains the same. The values of the activation barriers for both rotations at T > 173 K have the values, which are similar to those at 103―133 K. This indicates that the interaction potential defining these motions remains unchanged. The obtained data demonstrate that the detailed analysis of both line shape and anisotropy of spin-lattice relaxation represents a powerful tool to follow the evolution of the molecular reorientation mechanisms in organic solids.
QUADRUPOLAR METAL NMR OF OXIDE MATERIALS INCLUDING CATALYSTS
O.B. Lapina, V.V. Terskikh
Encyclopedia of Magnetic Resonance, Eds. R.K Harris, R.E Wasylishen, John Wiley & Sons, Ltd, 2011.
In this work, the authors review the basic methodology and recent applications of quadrupolar metal solid-state NMR spectroscopy in oxide systems with emphasis on materials science and catalysis. Three typical quadrupolar metal nuclei, 51V, 93Nb, and 95Mo, are discussed in detail to illustrate the complex interplay between the quadrupolar and chemical shielding interactions in oxides. In the first part, a systematic overview is given of the metal coordination environments in oxides and their corresponding NMR parameters. The importance of quantum chemical calculations in correlating experimental NMR results with a molecular level oxide structure is highlighted. In the second part, examples of quadrupolar metal NMR in materials science are presented, including paramagnetic oxide systems, layered materials, ferroelectrics, silicates, and glasses. The final section is dedicated to the latest applications of NMR in heterogeneous oxide catalysis.
MULTINUCLEAR NMR STUDY OF SILICA FIBERGLASS MODIFIED WITH ZIRCONIA
O.B. Lapina, D.F. Khabibulin, V.V. Terskikh
Solid State Nucl. Magn. Reson., 39(3-4) (2011) pp. 47-57.
Silica fiberglass textiles are emerging as uniquely suited supports in catalysis which offer unprecedented flexibility in designing advanced catalytic systems for chemical and auto industries. During manufacturing fiberglass materials are often modified with additives of various nature to improve glass properties. Glass network formers, such as zirconia and alumina, are known to provide the glass fibers with higher strength and to slow down undesirable devitrification processes. In this work multinuclear 1H, 23Na, 29Si, and 91Zr NMR spectroscopy was used to characterize the effect of zirconia on the molecular-level fiberglass structure. 29Si NMR results help in understanding why zirconia-modified fiberglass is more stable towards devitrification comparing with pure silica glass. Internal void spaces formed in zirconia-silica glass fibers after acidic leaching correlate with sodium and water distributions in the starting bulk glass as probed by 23Na and 1H NMR. These voids spaces are important for stabilization of catalytically active species in the supported catalysts. Potentials of high-field 91Zr NMR spectroscopy to study zirconia-containing glasses and similarly disordered systems are illustrated.
MECHANOCHEMICAL SYNTHESIS OF γ-LiAlO2 STUDIED BY 6Li AND 27Al NMR AND SYNCHROTRON X-RAY DIFFRACTION
V.P. Isupov*, O.A. Kharlamova*, L.E. Chupakhina*, M.R. Sharafutdinov*, D.F. Khabibulin, O.B. Lapina (*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia)
Inorg. Mater., 47(7) (2011) pp. 763-767.
The structural transformations accompanying the mechanochemical synthesis of fine-particle γ-LiAlO2 have been studied by 6Li and 27Al NMR and in situ X-ray diffraction. Mechanical activation of a mixture of aluminum hydroxide and lithium carbonate in an AGO-2 planetary mill results not only in size reduction, intermixing, and partial amorphization of the starting materials but also in the mechanochemical synthesis of a carbonate form of aluminum lithium hydroxide. Subsequent heat treatment of the mechanically activated mixture leads to the release of water and carbon dioxide molecules and the formation of an X-ray amorphous phase containing aluminum in octahedral and tetrahedral oxygen coordination. The X-ray amorphous material converts to gamma lithium aluminate through an intermediate phase.
BOROTUNGSTATE POLYOXOMETALATES: MULTINUCLEAR NMR STRUCTURAL CHARACTERIZATION AND CONVERSIONS IN SOLUTIONS
R.I. Maksimovskaya, G.M. Maksimov
Inorg. Chem., 50(11) (2011) pp. 4725-4731.
The unique heteropolyanion [H3BW13O46]8– (BW13), previously suggested on the basis of indirect evidence, and protonated lacunary heteropolyanion [HBW11O39]8– (BW11) have been identified in aqueous solutions at pH 5–7.5 from NMR spectra. The pattern of tungsten–tungsten connectivities based on the analysis of the 2JW–O–W coupling satellites in the 183W NMR spectrum of BW11, containing six peaks of relative intensities ~2:2:2:1:2:2, indicates that the latter is the α isomer. The 17O NMR spectrum confirms the protonated state of the polyanion with the proton delocalized on two out of four terminal O atoms surrounding the tungsten vacancy. The 183W NMR spectrum of BW13 contains seven peaks of relative intensities ~2:1:2:2:2:2:2 with additional large couplings due to the connectivity between BW11 and [W2O7]2– fragments. According to the 17O NMR spectrum, two protons of [BW13O46H3]8– are delocalized on the two terminal trans O atoms of the dimeric fragment while the third one is linked to its bridging O atom. The conversions of BW11 and BW13 in solution were followed by using 183W NMR spectra at a “fingerprint” level. In the pH range from ~7.5 to 6, BW11 transforms to BW13, transforming further to [BW12O40]5– (BW12) and [B3W39O132Hn]n-21 (B3W39) in different ratios. Conversion of BW13 to BW12 proceeds through an intermediate complex of suggested composition [BW11O39·WO2]7–. At high acidity (pH ~0), B3W39 gradually decomposes into tungstic acid, BW12 and H3BO3. Polyanion BW12 persists in the pH range ~0–7.5.
A STUDY OF THE HYDROLYSIS OF ZrF62-AND THE STRUCTURE OF INTERMEDIATE HYDROLYSIS PRODUCTS BY 19F AND 91Zr NMR IN THE 9.4 T FIELD
M.A. Fedotov, A.V. Belyaev* (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
J. Struct. Chem., 52(1) (2011) pp. 69-74.
The high-field 19F and 91Zr NMR method is used to study the hydrolysis and polycondensation of hexafluorozirconate ZrF62- in aqueous and water-peroxide solutions. During hydrolysis in aqueous solutions only ZrF62- and F- ions were observed by NMR, however, in the water-peroxide medium, an intermediate product of hydrolysis ([F5Zr-OO-ZrF5]4-dimer) was detected. The dimer structure is confirmed by 19F and 91Zr NMR. In high fields (19F NMR frequency > 200 MHz), the fluorine exchange between ZrF62- and F- is slow in the 19F NMR scale and has a multisite character.
SOLID-PHASE CONDENSATION OF RHODIUM(III) AQUA SULFATES
S.N. Vorob’eva*, A.V. Belyaev*, M.A. Fedotov, I.V. Yushina*, T.I. Nedoseikina* (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
Russ. J. Inorg. Chem., 56(10) (2011) pp. 1609-616.
Solid-phase condensation of rhodium(III) aqua sulfates yielding oligomeric rhodium(III) aqua sulfate complexes was revealed. The isothermal dehydration of rhodium(III) aqua sulfates under thermal diffusion conditions in the temperature range 100–130°C was studied, and effective rate constants and activation energies were determined. The solid phases of dehydration products were studied by X-ray powder diffraction and IR spectroscopy, and solutions of polymeric phases were studied by 103Rh and 17O NMR, electronic absorption spectroscopy, chromatography, and electrophoresis.
PLATINUM(IV) COMPLEXATION WITH THE NITRATE ION IN AQUEOUS SOLUTIONS ACCORDING TO 195Pt, 15N, 14N, AND 17O NMR DATA
A.V. Belyaev*, M.A. Fedotov, S.N. Vorobieva* (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
Russ. J. Coord. Chem., 37(4) (2011) pp. 281-287.
Solutions of platinum(IV) nitrate were studied by 195Pt, 15N, 14N, and 17O NMR and IR and Raman spectroscopy. It was found that in nitric acid, two interrelated systems of nitrate complexes, mono- and polynuclear ones, coexist. The complexes predominating in concentrated solutions are [Pt2(μ-OH)(μ-NO3)(NO3)2(H2O)6-x(OH)x](4-x)+, [Pt4(μ-OH)3(μ-NO3)3(NO3)3(H2O)9-x(OH)x](7-x)+, [Pt4(μ-OH)4(μ-NO3)2(NO3)4(H2O)8-x(OH)x](6-x)+, and [Pt4(μ-OH)6(NO3)3(H2O)16-x(OH)x ](7-x)+.
THE INFLUENCE OF AN EXOTHERMIC REACTION ON THE SPATIAL DISTRIBUTION OF THE LIQUID PHASE IN A TRICKLE BED REACTOR: DIRECT EVIDENCE PROVIDED BY NMR IMAGING
A.A. Lysova, A. Von Garnier*, E.H. Hardy**, R. Reimert*, I.V. Koptyug*** (*Karlsruhe Institute of Technology, Karlsruhe, Germany; **International Tomography Center, Novosibirsk, Russia)
Chem. Eng. J., 173(2) (2011) pp. 552-563.
In this paper, NMR imaging was applied to study the distribution of the liquid phase in a fixed catalyst bed of an operating multiphase reactor with a cocurrent gas-liquid flow under conditions when the heterogeneous catalytic hydrogenation of 1-octene was taking place in the reactor. The 2D maps of the spatial distribution of the external and internal liquid holdups in the various regimes of the catalyst bed operation have been obtained for the first time in the course of the reaction. It was shown by a direct in situ method that an exothermic reaction taking place in a trickle bed reactor dramatically affected the distribution of the liquid phase in the catalyst bed. In particular, in the presence of the reaction, the catalyst bed was characterized by a non-uniform distribution of the liquid phase, as revealed by evaluating the external and internal liquid holdups. In the absence of the reaction, the bed was largely filled with the liquid phase.
PROBING THE DYNAMICS OF CO2 AND CH4 WITHIN THE POROUS ZIRCONIUM TEREPHTHALATE UiO-66(Zr): A SYNERGIC COMBINATION OF NEUTRON SCATTERING MEASUREMENTS AND MOLECULAR SIMULATIONS
Q. Yang*,****, H. Jobic**, F. Salles*, D.I. Kolokolov, V. Guillerm***, Ch. Serre***, G. Maurin* (*Institut Charles Gerhardt Montpellier, Universit Montpellier II, Montpellier CEDEX, France; **Institut de Recherches sur la Catalyse et l’Environnement de Lyon, Villeurbanne, France; ***Institut Lavoisier, Versailles, France; ****Beijing University of Chemical Technology, Beijing, P.R. China)
Chem. Eur. J., 17(32) (2011) pp. 8882-8889.
Quasi-elastic neutron scattering (QENS) measurements combined with molecular dynamics (MD) simulations were conducted to deeply understand the concentration dependence of the self-and transport diffusivities of CH4 and CO2, respectively, in the humidity-resistant metal–organic framework UiO-66(Zr). The QENS measurements show that the self-diffusivity profile for CH4 exhibits a maximum, while the transport diffusivity for CO2 increases continuously at the loadings explored in this study. MD simulations can reproduce fairly well both the magnitude and the concentration dependence of each measured diffusivity. The flexibility of the framework implemented by deriving a new forcefield for UiO-66(Zr) has a significant impact on the diffusivity of the two species. Methane diffuses faster than CO2 over a broad range of loading, and this is in contrast to zeolites with narrow windows, for which opposite trends were observed. Further analysis of the MD trajectories indicates that the global microscopic diffusion mechanism involves a combination of intracage motions and jump sequences between tetrahedral and octahedral cages.
NMR IMAGING OF HEAVY CRUDE OIL FOR SOFTENING DETECTION UNDER HEAT TREATMENT
E.V. Morozov*, O.N. Martyanov, N.V. Volkov*, O.V. Falaleev* (*Kirensky Institute of Physics, Krasnoyarsk, Russia)
J. Mater. Sci. Eng. A, 1 (2011) pp. 545-551.
NMR imaging results of Mongolian heavy crude oil samples subjected to heat treatment are presented in this work. Abundance of dotted inhomogeneities related with high paraffinicity of heavy oil was obtained during imaging investigation. Behavior of heavy oil subjected to heat treatment, dotted inhomogeneities changes, softening and dynamic of melting front were visualized by means of imaging techniques based on both gradient and spin echo. Softening forestalling over the melting front are demonstrated using artificial mark in the form of water drop deposited on the oil surface. In results the NMR imaging proved to be highly effective for investigation of impurity agglomerates in heavy oil engineering development.
ELECTRON SPIN RESONANCE OF VO2+ RADICAL-ION IN SUB- AND SUPERCRITICAL WATER
S.N. Trukhan, V.F. Yudanov, O.N. Martyanov
J. Supercrit. Fluids, 57(3) (2011) pp. 247-250.
Electron spin resonance (ESR) spectra of VO2+ radical-ions in sub- and supercritical water are observed. Upon increasing the temperature from 20 to 100°C, the fine structure line widths in the ESR spectra of the vanadyl ion are observed to be reduced that is associated with the effective averaging of the g-factor anisotropy and the hyperfine interaction. With further increasing the temperature, the spectrum components of the hyperfine structure are broadened significantly resulting in the unresolved low-intensity line in supercritical water with ΔHpp ∼ 300 G. The data obtained allow behavior peculiarities of the paramagnetic VO2+ ions in sub- and supercritical water including rotational dynamics and spin exchange between the radicals to be elucidated. The registration of the unresolved low-intensity line in supercritical conditions points to an increase in the local ion concentration in the system that can be an initial stage for the formation of vanadium-based particles in supercritical conditions. The study demonstrates that ESR is the powerful tool to investigate properties of sub- and supercritical water in situ.
THE CHARACTERISTICS OF NEW PERMANENT SORBENT–MODIFIERS FOR THE HYDRIDE ATOMIC ABSORPTION SPECTROMETRIC DETERMINATION OF ARSENIC WITH TRAPPING OF THE ARSINE IN A GRAPHITE FURNACE
M.Yu. Burylin*, V.I. Zaikovsky, K.A. Romanovsky*, P.R. Arushanian* (*Kuban
State University, Krasnodar, Russia)
Anal. & Control, 15(1) (2011) pp. 23-36.
The characteristics of new Zr–Ir and W–Ir permanent sorbent–modifiers on the carbonized basis for the determination of arsenic by electrothermal atomic absorption spectrometry (ETAAS) with trapping within a graphite (GF) furnace were studied. The results of the electron microscopic investigation, local X-ray elemental analysis and electron microdiffraction corroborated zirconium and tungsten carbide’s formation. The particle sizes of these
compounds are from 50 to 200 nm. The iridium component presents as nanoparticles (5-10 nm) of condensed systems with the carbide forming metal. There is even distribution of the particles on the basis. Achievement of necessary purity’s level of the permanent systems during their synthesis in a graphite furnace is confirmed. The parameters of the stage of arsine trapping by new sorbent-modifiers and arsenic’s atomization stage are studied: temperature of trapping stage, velocity of reagent’s entering, time of trapping stage, temperature of atomization stage. The optimized conditions were used for the determination of As in natural surface-water. The limits of detection were 7 ng/l and 5 ng/l for the Zr-Ir modifier and W-Ir modifier respectively.
METHANE CONVERSION INTO AROMATIC HYDROCARBONS OVER Ag–Mo/ZSM-5 CATALYSTS
A.V. Vosmerikov*, V.I. Zaikovsky, L.L. Korobitsyna*, V.V. Kozlov*, N.V. Arbuzova*, S.P. Zhuravkov** (*Institute of Petroleum Chemistry, Tomsk, Russia; **Tomsk Polytechnic University, Tomsk, Russia)
Kinet. Catal., 52(3) (2011) pp. 427-433.
Nonoxidative methane conversion into aromatic hydrocarbons over ZSM-5-type high-silica zeolites modified with nanosized powders of molybdenum (4.0 wt%) and silver (0.1–0.5 wt%) is reported. The acidic properties of the catalysts have been investigated by temperature-programmed ammonia desorption. The microstructure and composition of the Ag-Mo/ZSM-5 catalytic systems have been studied by high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy. The doping of the Mo containing zeolite with silver enhances its activity and stability in nonoxidative methane conversion into aromatic hydrocarbons.
SUBMICROMETER INTERMEDIATES IN THE CITRATE SYNTHESIS OF GOLD NANOPARTICLES: NEW INSIGHTS INTO THE NUCLEATION AND CRYSTAL GROWTH MECHANISMS
Yu.L. Mikhlin*, A.A. Karacharov*, M.N. Likhatski*, T.Yu. Podlipskaya**, Ya.V. Zubavichus***, A.A. Veligzhanin***, V.I. Zaikovsky (*Institute of Chemistry and Chemical Technology, Krasnoyarsk, Russia; **Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; ***National Research Centre “Kurchatov Institute”, Moscow, Russia)
J. Colloid Interf. Sci., 362(2) (2011) pp. 330-336.
The reduction of tetrachloroaurate by citrate ions in aqueous solutions yielding gold nanoparticles (GNPs) has been studied using in situ tapping mode atomic force microscopy (AFM), UV-vis absorption and dynamic light scattering (DLS) spectroscopies, small-angle X-ray scattering (SAXS) along with ex situ TEM, EDX and XPS. Special attention is given to mesoscale intermediates responsible for the intense coloring of the transient solutions and their role in nucleation and crystal growth. AFM detects liquid droplet-like domains, globules 30-50 nm in diameter arranged in submicrometer aggregates in the gray and blue solutions, and well separated individual particles in the final red sols. DLS shows abrupt appearance of species about 30 nm and larger but not growing Au nanoparticles, while SAXS reveals gradually increasing nanoparticles and no aggregates. The mesoscale structures observed in TEM become looser as the reaction proceeds; they contain signatures of oxidized Au and other solutes. The results are interpreted in terms of decomposition of supersaturated solutions to afford domains (“dense droplets”) enriched by gold, and then, after nucleation and coalescence of Au nuclei inside them, rather slow growth of gold nanoparticles within the associated globules; the color changes of the transient solutions are due to increasing interparticle distances.
KINETICS AND MECHANISM OF THE GROWTH OF GOLD NANOPARTICLES BY REDUCTION OF TETRACHLOROAURIC ACID BY HYDRAZINE IN Triton N-42 REVERSE MICELLES
V.V. Tatarchuk*, A.P. Sergievskaya*, I.A. Druzhinina*, V.I. Zaikovsky (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia)
J. Nanopart. Res., 13(10) (2011) pp. 4997-5007.
The kinetics of the growth of gold nanoparticles during the reduction of tetrachloroauric acid by hydrazine in dispersed aqueous solution encapsulated by reverse micelles of Triton N-42 surfactant (with decane as dispersion medium) was studied by means of spectrophotometry. According to DLS data, at a set value of solubilization capacity Vs/Vo = 0.005 initial micelles have an aqueous core hydrodynamic diameter dc = 3.6±0.2 nm. The final particles obtained after full reduction of AuIII have a metallic core of defect-free single-crystalline gold with a narrow size distribution and average core diameter dAu = 7.7 ± 1.4 nm as shown by TEM. The rate of the particle growth is limited by the rate of gold reduction. The process kinetics corresponds to the model consisting of two stages of reduction AuIII → AuI → Au0. The stages involve the formation and redox decay of the intermediate complexes Au(N2H4)Cl3 and Au(N2H4)Cl, and each stage proceeds via two routes:
THE AGEING OF SILICA GELS AFFECTED BY HYDROTHERMAL TREATMENT
W. Lutz*, M. Weber**, R. Bertram***, R. Kurzhals****, G.N. Kryukova
(*Brandenburgische Technische Universität Cottbus, Berlin, Germany; **SCW Process Technology Development GmbH, Berlin, Germany; ***Leibniz-Institut für Kristallzüchtung, Berlin, Germany; ****Süd-Chemie Zeolites GmbH, Bitterfeld-Wolfen, Germany)
Z. Anorg. Allg. Chem., 637(3-4) (2011) pp. 421-425.
Commercial silica gels of the pyrogenic and precipitated types were hydrothermally treated for 72 hours at temperatures between 90°C and 210°C in water of autogenous pressure. The samples were characterised by IR spectroscopy, water and nitrogen adsorption. Stability and sorption capacity run similarly. The more Q4 (Si(OSi)4) building units the framework of a silica gel contained, the lower was its sorption capacity. Sorption capacity increased with rising number of structural defects characterised by the presence of Q3 (Si(OSi)3OH) and Q2 (Si(OSi)2(OH)2) groups. Simultaneously, the hydrothermal stability of the silica material dropped off.
REACTIVITY OF EXTRA-FRAMEWORK SPECIES OF USY ZEOLITES IN ALKALINE MEDIUM
W. Lutz*, R. Bertram**, D. Heidemann***, R. Kurzhals****, C. Ruscher*****, G.N. Kryukova (*Lehrstuhl fur Luftchemie und Luftreinhaltung Brandenburgische Technische Universitat Cottbus, Berlin, Germany; **Leibniz-Institut fur Kristallzuchtung, Berlin, Germany; ***Institut fur Chemie Humboldt-Universitat zu Berlin, Berlin, Germany; ****Sud-Chemie Zeolites GmbH, Bitterfeld-Wolfen, Germany; *****Universitat Hannover, Hannover, Germany)
Z. Anorg. Allg. Chem., 637(1) (2011) pp. 75-82.
Zeolites of type USY (ultra-stable Y) were obtained by steaming of NH4NaY modification. Samples were modified by subsequent alkaline treatment in KOH solution. USY and USY-KOH were characterised by chemical element analysis, XRD, IR, 29Al and 29Si MAS NMR spectroscopic measurements. Correct silicon to aluminium ratios (Si/Al) were determined by XRD and IR (double ring vibration wDR) data whereas values calculated according to data of 29Si MAS NMR and IR spectroscopy (asymmetrical TOT valence vibration wTOT) appeared to be too high. In the latter case, the signals of the zeolite framework were strongly superimposed by that of extra-framework silica gel (EFSi) formed during steaming. It was found that alkaline leaching induces desilication of silicon-rich area of the zeolite framework and partial dissolution of EFSi. Silicate ions of both react with likewise dissolved extra-framework aluminium (EFAl) to form X-ray amorphous aluminosilicate. Consequently, the superposition of the 29Si MAS NMR signals of the zeolite framework by silica gel was reduced for Q4(0Al) but increased for Q4 (2Al) and Q4(3Al) structure units. A reinsertion of EFAl into the zeolite framework has not been observed.
LIGHT SCATTERING IN A SURFACE GLASS LAYER PRODUCED BY A SURFACE ION EXCHANGE PROCESS AND COATED WITH THIN GOLD LAYERS
O.N. Sidel’nikova*, G.A. Pozdnyakov**, A.N. Serkova, A.N. Salanov (*Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russia; **Khristianovich Institute of Theoretical and Applied Mechanics, Novosibirsk, Russia)
Glass Technol., 52(1) (2011) pp. 15-22.
The morphology and optical properties of a glass surface treated by a surface ion exchange process and coated with a thin surface gold layer are investigated. It was found by SEM that the modified surface layer consists of a system of microblocks and microcracks. In addition the thin gold layer consists of nanosized hemispherical gold nucleation centers of volume growth (diameters ∼100-500 nm), three-dimensional gold aggregates and pendant “cornice”. The investigated optical properties (light scattering, depolarization, light loss characteristics and effectiveness of light propagation) differ significantly from the analogous optical data previously reported for glass surface modified by the same surface ion exchange process but lacking the thin gold layer. The results are also compared with results obtained from a chemically etched glass surface. The obtained data may be important and useful in glass illumination engineering, light decoration and others fields.
METHOD OF SPECTRAL SUBTRACTION OF GAS-PHASE FOURIER TRANSFORM INFRARED (FT-IR) SPECTRA BY MINIMIZING THE SPECTRUM LENGTH
D.V. Kozlov, A.S. Besov
Appl. Spectrosc., 65(8) (2011) pp. 918-923.
A new method of spectral subtraction for gas-phase Fourier transform infrared (FT-IR) spectra was developed for long-path gas measurements. The method is based on minimization of the length of the spectrum that results from subtracting the spectrum of an individual component of a gas mixture (water, CO2, etc.) from the experimental spectrum of the mixture. For this purpose a subtraction coefficient (kmin) is found for which the length of the resulting spectrum is minimized. A mathematical simulation with two Lorentzian absorption bands was conducted and the limits of application for the proposed method were determined. Two experimental examples demonstrate that a successful result could be achieved in the case when the subtrahend spectrum contains a number of narrow absorption bands (such as the spectrum of water vapor).
In situ FTIR STUDY OF β-PICOLINE TRANSFORMATIONS ON V–Ti–O CATALYSTS
G.B. Chernobay, Yu.A. Chesalov, V.P. Baltakhinov, G.Ya. Popova, T.V. Andrushkevich
Catal. Today, 164(1) (2011) pp. 58-61.
Surface complexes formed during β-picoline transformations on V–Ti–O catalysts in the temperature range of 120–300°C were studied using in situ FTIR spectroscopy. Two vanadia–titania catalysts with several kinds of vanadia species were used in experiments. FTIR spectra have revealed differences in composition of surface complexes under different coverage, which could be related to different ways of transformations of intermediate pyridine-3-carbaldehyde.
O– RADICAL ANIONS ON OXIDE CATALYSTS: FORMATION, PROPERTIES, AND REACTIONS
A.M. Volodin, S.E. Malykhin, G.M. Zhidomirov
Kinet. Catal., 52(4) (2011) pp. 605-619.
A systematic in situ EPR study of processes yielding O– radical anions on the surface of oxide dielectrics (MgO, CaO), semiconductors (ZnO, TiO2), supported systems (V/SiO2), and zeolite FeZSM-5 is reported. Methodological approaches to the study of O– radical anions are considered for the cases in which these species are directly undetectable by EPR. Particular attention is focused on the development of methods of investigation of so-called α-oxygen on the FeZSM-5 surface, which is an O– radical anion stabilized on the paramagnetic ion Fe3+. The reactions involving α-oxygen and the analogous reactions known for O– radical anions stabilized on the oxide surface are demonstrated to occur in similar ways. The photostimulated formation of spatially separated electron and hole centers on the surface of oxide systems is most likely due not to charge separation, but to the spatial separation of the radicals resulting from the homolytic photodissociation of chemisorbed water. A scheme is suggested for this process on the partially hydroxylated MgO surface.
EXPLORING BY PULSED EPR THE ELECTRONIC STRUCTURE OF UBISEMIQUINONE BOUND AT THE QH SITE OF CYTOCHROME bo3 FROM ESCHERICHIA COLI WITH in vivo 13C-LABELED METHYL AND METHOXY SUBSTITUENTS
M.T. Lin*, A.A. Shubin, R.I. Samoilova**, K.V. Narasimhulu*, A. Baldansuren*, R.B. Gennis*, S.A. Dikanov (*University of Illinois at Urbana-Champaign, Urbana, Illinois; **Institute of Chemical Kinetics and Combustion, Novosibirsk, Russia)
J. Biol. Chem., 286(12) (2011) pp. 10105-10114.
The cytochrome bo3 ubiquinol oxidase from Escherichia coli resides in the bacterial cytoplasmic membrane and catalyzes the two-electron oxidation of ubiquinol-8 and four-electron reduction of O2 to water. The one-electron reduced semiquinone forms transiently during the reaction, and the enzyme has been demonstrated to stabilize the semiquinone. The semiquinone is also formed in the D75E mutant,
where the mutation has little influence on the catalytic activity, and in the D75H mutant, which is virtually inactive. In this work, wild-type cytochrome bo3 as well as the D75E and D75H mutant proteins were prepared with ubiquinone-8 13C-labeled selectively at the methyl and two methoxy groups. This was accomplished by expressing the proteins in a methionine auxotroph in the presence of l-methionine with the side chain methyl group 13C-labeled. The 13C-labeled quinone isolated from cytochrome bo3 was also used for the generation of model anion radicals in alcohol. Two-dimensional pulsed EPR and ENDOR were used for the study of the 13C methyl and methoxy hyperfine couplings in the semiquinone generated in the three proteins indicated above and in the model system. The data were used to characterize the transferred unpaired spin densities on the methyl and methoxy substituents and the conformations of the methoxy groups. In the wild type and D75E mutant, the constraints on the configurations of the methoxy side chains are similar, but the D75H mutant appears to have altered methoxy configurations, which could be related to the perturbed electron distribution in the semiquinone and the loss of enzymatic activity.
SIZE-DEPENDENT EFFECTS IN EPR AND LUMINESCENCE SPECTRA OF NH4BPh4 EXCITED STATES: FROM BULK TO NANOPARTICLES
O.V. Antonova*, V.A. Nadolinny*, E.A. Il'inchik*, M.K. Kovalev, A.P. Yelisseyev** (*Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia; **Institute of Geology & Mineralogy, Novosibirsk, Russia)
Appl. Magn. Reson., 40(4) (2011) pp. 459-469.
Photoexcited states of NH4BPh4 (TPhBA) particles embedded in mesoporous frameworks of different pore sizes were studied by combined electron paramagnetic resonance (EPR), optical and photoluminescence techniques. A distribution of triplet states with short and long electron-hole distances was found. While EPR studies on TPhBA bulk sample suggested that the formation of electron-hole pairs upon the excitation was caused by electron capture on electron traps, the samples in mesoporous frameworks exhibit two ways of the pair formation. The first one is attributed to the capture on phenyl rings and another one is to be thought as the capture of electrons on adsorbed oxygen molecules. These results are also consistent with the thermoluminescence spectra and EPR studies of the photoexcited samples during annealing.
EFFECT OF Cs+ PROMOTER IN Ru/MgO CATALYSTS
J. Phys. Chem. C, 115(3) (2011) pp. 631-635.
Ru/MgO and Ru-Cs+/MgO catalysts were prepared from Ru(OH)Cl3 and were studied by XPS, TEM, CO chemisorption, and EXAFS. An explanation for the large differences in sizes of Ru particles measured by TEM and XRD compared to those determined by CO chemisorption is proposed. This explanation is based on the XPS data that the initial catalyst Ru/MgO consists of Ru0 metal particles and RuO2 clusters. The latter are not measured by CO chemisorption and have high stability due to RuO2-MgO interaction. A new feature of Cs+ promoter influence on the Ru/MgO catalyst was found. The addition of Cs+ to the Ru/MgO catalyst, which contains Ru partly in the oxidized form, does not lead to the formation of any cesium ruthenates. Instead, the cesium promoter reduces the RuO2 clusters, which are stabilized by epitaxy interaction with the support, to form the Ru0 particles. This new feature of Cs+ promoter results in the increase of supported Ru useful ratio and Ru-specific surface area in these catalysts.
ELECTRONIC STATE OF RUTHENIUM DEPOSITED ONTO OXIDE SUPPORTS: AN XPS STUDY TAKING INTO ACCOUNT THE FINAL STATE EFFECTS
Yu.V. Larichev, B.L. Moroz, V.I. Bukhtiyarov
Appl. Surf. Sci., 258(4) (2011) pp. 1541-1550.
The electronic state of ruthenium in the supported Ru/EOx (EOx = MgO, Al2O3 or SiO2) catalysts prepared with the use of Ru(OH)Cl3 or Ru(acac)3 (acac = acetylacetonate) and reduced with H2 at 723 K is characterized by X-ray photoelectron spectroscopy (XPS) in the Ru 3d, Cl 2p and O 1s regions. The influence of the final state effects (the differential charging and variation of the relaxation energy) on the binding energy (BE) of Ru 3d5/2 core level measured for supported Ru nanoparticles is estimated by comparison
of the Fermi levels and the modified Auger parameters determined for the Ru/EOx samples with the corresponding characteristics of the bulk Ru metal. It is found that the negative shift of the Ru 3d5/2 peak which is observed in the spectrum of ruthenium deposited onto MgO (BE = 279.5–279.7 eV) with respect to that of Ru black (BE = 280.2 eV) or ruthenium supported on γ-Al2O3 and SiO2 (BE = 280.4 eV) is caused not by the transfer of electron density from basic sites of MgO, as considered earlier, but by the differential charging of the supported Ru particles compared with the support surface. Correction for the differential charging value reveals that the initial state energies of ruthenium in the Ru/EOx systems are almost identical (BE = 280.5 ± 0.1 eV) irrespectively of acid–base properties of the support, the mean size of supported Ru crystallites (within the range of 2–10 nm) and the surface Cl content. The results obtained suggest that the difference in ammonia synthesis activity between the Ru catalysts supported on MgO and on the acidic supports is accounted for by not different electronic state of ruthenium on the surface of these oxides but by some other reasons.
SMALL-ANGLE SCATTERING STUDY OF COLLOIDAL PARTICLES IN HEAVY CRUDE OILS
F.V. Tuzikov, Yu.V. Larichev, L.S. Borisova*, I.V. Kozhevnikov, O.N. Martyanov (*Trofimuk Institute of Petroleum Geology and Geophysics, Novosibirsk, Russia)
Pet. Chem., 51(4) (2011) pp. 281-285.
The structural and dispersion characteristics of samples of heavy crude oils and fractions isolated from them have been studied. A method of in situ analysis of the aggregation of asphaltenes directly in crude oils on the basis of small-angle X-ray scattering is proposed. It has been shown that the maximum size of scattering particles in all crude oil samples is limited to the value on the order of 8.0 nm; the average diameter is ~2.0 nm. It has been found that the fraction with sizes of 0.8–2.5 nm is mostly composed of resins. Asphaltenes in crude oils form larger aggregated particles with a size up to 8 nm. A comparative study of model dilute solutions of asphaltenes in toluene (0.23 wt%) has shown that the major part of asphaltenes in the liquid (~94%) is in the form of individual molecules with a size of 0.4–1.2 nm, and only an insignificant remaining part (~6%) occurs in the form of large aggregates.
INFLUENCE OF ATORVASTATIN ON SERUM LIPIDS ON MICE WITH LIPEMIA
V.M. Loginova*, F.V. Tuzikov, N.A. Tuzikova, M.S. Cherkanova*, E.E. Filyushina*, T.A. Korolenko* (*Institute of Physiology, Novosibirsk, Russia)
Bull. SB RAMS, 31(2) (2011) pp. 133-137.
Atorvastatin (75 mg/kg) was administered twice in ICR mice with acute lipemia induced with a single injection of Triton WR 1339 (500 mg/kg). A novel small-angle X-ray scattering (SAXS) method for the determination of fractional and subfractional composition of C-LP was used. In Triton WR 1339-treated animals, there was a drastic increase of atherogenic low-density C-LP (C-LDL) fraction, intermediate density lipoprotein-cholesterol (C-IDL) subfraction, and very low-density C-LP (C-VLDL) fractions (C-VLDL3-5 subfraction), with an increase of the C-HDL3 subfraction. Atorvastatin treatment of lipemia was followed a decrease in the total C and, especially, a decrease in the TG concentration, by normalization of atherogenic C-LDL fraction, C-IDL subfraction, and a decrease of C-VLDL (C-VLDL3-5 subfraction).
INFLUENCE OF ATORVASTATIN ON FRACTIONAL AND SUBFRACTIONAL COMPOSITION OF SERUM LIPOPROTEINS AND MMP ACTIVITY IN MICE WITH TRITON WR 1339-INDUCED LIPAEMIA
T.A. Korolenko*, M.S. Cherkanova*, F.V. Tuzikov, T.P. Johnston**, N.A. Tuzikova, V.M. Loginova*, V.I. Kaledin* (*Institute of Physiology, Novosibirsk, Russia; **University of Missouri-Kansas City, Kansas City, Missouri, USA)
J. Pharm. Pharmacol., 63(6) (2011) pp. 833-839.
The effects of atorvastatin on the atherogenic and anti-atherogenic lipoprotein-cholesterol (C-LP) and lipoprotein-triglyceride (TG-LP) fractions and subfractions at the early stage of murine acute hyperlipidaemia, and its pleiotropic anti-inflammatory effects via the activity of matrix metalloproteinases (MMPs) were studied.
Atorvastatin (75 mg/kg) was administered to ICR mice with acute lipaemia induced by a single injection of Triton WR 1339 (500 mg/kg). A novel small-angle X-ray scattering (SAXS) method was used for the determination of the fractional and subfractional composition of C-LP and TG-LP. In Triton WR 1339-treated mice, there was a drastic increase in the atherogenic low-density C-LP (C-LDL) fraction, intermediate density lipoprotein-cholesterol (C-IDL) subfraction, and very low-density C-LP (C-VLDL) fractions (C-VLDL(3-5) subfraction). Additionally, there was an increase in the C-HDL(3) subfraction. Treatment of lipaemia with atorvastatin resulted in the normalization of the atherogenic C-LDL fraction and the C-IDL subfraction. A decrease in C-VLDL (C-VLDL(3-5) subfraction), total cholesterol and, especially, triglyceride (TG) concentrations was also demonstrated. Similar results were obtained with the TG-LP fractions and subfractions. Additionally, atorvastatin treatment resulted in an increase in the serum and liver MMP activity.
STUDY OF CdSe/CdS QUANTUM DOTS IN SOLUTIONS AND GELS BY SMALL-ANGLE X-RAY SCATTERING
N.B. Simonova*, F.V. Tuzikov, R.N. Khramov*, N.A. Tuzikova, M.F. Tuzikov*, M.S. Vakshtein**
(*Institute of Theoretical and Experimental Biophysics, Pushchino, Moscow oblast, Russia; **Federal State Unitary Association Research Institute of Applied Acoustics, Dubna, Moscow oblast, Russia)
J. Surf. Invest. - X-Ray Synchrotron Neutron Techn.,
5(1) (2011) pp. 126-133.
The sizes of semiconductor nanocrystals of CdSe/CdS quantum dots (QDs) synthesized by the colloidal method were estimated using small-angle X-ray scattering. The distribution of QD nanocrystals in organic solvents of different polarities and in polymer gels and matrices is studied. Structural invariants of scattering QD particles (heterogeneities of the electron density) — namely, inertia radii and sizes, forms, and dispersive composition of particles — are determined. The contribution of scattering by QDs in solutions and gels is calculated. The effective sizes of particles and their aggregates are determined, and the parameters of the distribution over the QD sizes in organic solvents and polymer matrices are estimated. The typical distance between particles in samples is determined. The position of the maximum at the beginning of the small-angle scattering curves corresponds to the distance dm = 2π/h0 between the planes (here, h0 is the position of the maximum on the
scale h). It is 74–76.9 Å for solutions, 60 Å for gels, and 99 Å for polymer matrices with concentrations of up to 0.15% and 77 Å for those with the concentrations exceeding 0.15%, which is close to the estimation of the sizes of separate CdSe QDs that was obtained from the distribution histograms (60–80 Å). This result shows that CdSe/CdS QDs introduced in the polymer matrices disperse to form either separate particles or small aggregates and located at a distance on the order of 80 Å from each other.
SPECIFIC FEATURES OF ASSOCIATION OF Cu2+ IONS IN CONCENTRATED AQUEOUS AMMONIA SOLUTIONS OF COPPER NITRATE AS PROBED BY ESR
V.F. Anufrienko, G.A. Zenkovets, R.A. Shutilov, V.Yu. Gavrilov, N.T. Vasenin, A.A. Shubin, Z.R. Ismagilov, V.N. Parmon
Doklady Phys. Chem., 440(2) (2011) pp. 194-197.
In this work, self-association of Cu2+ ions in aqueous ammonia solutions of copper nitrate was revealed for the first time.
It was shown that, in aqueous ammonia solutions of copper nitrate containing 10 g/L Cu in a wide range of ammonium ion concentrations, different types of Cu2+ associates with specific orbital ordering were formed. The ammonium concentration in a solution has a decisive effect on the type of orbital ordering of Cu2+ ions in associates. In all cases, copper ion ordering in associates is caused by the presence of bridging OH groups in the axial or equatorial position of [Сu(NH3)n(H2O)6–n]2+ complexes (n < 6).
BIMETALLIC Pd–M (M = Co, Ni, Zn, Ag) NANOPARTICLES CONTAINING TRANSITION METALS: SYNTHESIS, CHARACTERIZATION, AND CATALYTIC PERFORMANCE
B.G. Ershov*, A.V. Anan’ev*, E.V. Abkhalimov*, D.I. Kochubei, V.V. Kriventsov, L.M. Plyasova, I.Yu. Molina, N.Yu. Kozitsyna**, S.E. Nefedov**, M.N. Vargaftik**, I.I. Moiseev** (*Frumkin Institute of Physical Chemistry and Electrochemistry, Moscow, Russia; **Kurnakov Institute of General and Inorganic Chemistry, Moscow, Russia)
Nanotechn. Russia, 6(5-6) (2011) pp. 323-329.
The reductive thermolysis of Pd(OOCMe)4M(OH2) (M = NiII, CoII, ZnII) and Pd(OOCMe)4Ag2(HOOCMe)4 molecular complexes results in the generation of bimetallic Pd-based Pd–M (M = Co, Ni, Zn, Ag) nanoparticles. The composition and morphology of nanoparticles and the electron state of metal atoms were characterized using electron microscopy, elemental ICP analysis, X-ray diffraction, and XAFS (XANES/EXAFS) techniques. The catalytic performance of nanoparticles was studied using the example of reactions of catalytic hydrazine decomposition and U(VI) reduction to U(IV) by hydrazine and formic acid. The catalytic performance of Pd–Ni nanoparticles is superior to that of the standard supported Pd/SiO2 catalyst containing a similar amount of Pd atoms, while Pd–Co, Pd–Zn, and Pd–Ag Nanoparticles do not catalyze the studied reactions.