Influence of the composition of Co-containing perovskites on their catalytic properties in the conversion of methane into higher hydrocarbons in non-stationary conditions

The oxidative coupling of methane in a periodic regime was studied using Co-containing perovskites as solid oxidants. Partial substitution of strontium with alkali metals in the perovskite SrCoO₃ increased the activity and selectivity of the catalyst with respect to higher hydrocarbons. The substituted catalysts continued to work after many oxidation-reduction cycles. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 1, pp. 47–52, January–February, 2000.     

Modeling of the kinetics of the heterogeneous-homogeneous conversion of methane into ethane and ethylene in the absence of oxygen in the gas phase

Computer calculations were carried out on the kinetics of the gas phase chain process for the conversion of methyl radicals into higher hydrocarbons in an oxygen-free atmosphere based on a scheme of reactions consisting of 23 homogeneous elementary steps and the heterogeneous stage of methyl radical formation. The results of the calculations are in good agreement with experimental kinetic results obtained for the interaction of methane with the oxidized surface of the perovskite catalyst KNaSrCoO₃. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 03039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 4, pp. 222–225, July–August, 2000.     

The effect of sulfur dioxide on the activity of modified mordenites in the selective reduction of Nox

The results of a comparative investigation into the activity of modified natural and synthetic mordenites in the selective reduction of NO_x by C₁ and C₃−C₄ hydrocarbons (methane and a propane-butane mixture), the effect of sulfur dioxide on the process, and the acidic characteristics of the mordenites by temperature programmed desorption of ammonia and IR spectroscopy are presented. Sulfur dioxide has practically no effect on the selective reduction of NO_x by C₃−C₄ hydrocarbons at the H forms of synthetic and previously recationized natural mordenites but substantially retards the process at the Cu-, Co-, and Cr-substituted forms and palladium-containing mordenites. The decrease in the concentration of the strong B centers in the transition from the hydrogen to the copper-containing form of the mordenites reduces their activity in selective reduction. Prior recationization of natural mordenites increases their activity, stability, and resistance to the action of sulfur dioxide. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 2, pp. 119–124, March–April, 1999.     

Kinetics of the growth of the oxide layer during anodic oxidation of aluminum

Experimental plots of anode current density against time obtained for various electrolytes over a temperature range from 5 to 60°C have been compared with a theoretical model which describes the kinetics of the growth of the oxide film during anodic oxidation of aluminum. It is concluded from differences in the kinetic parameters for ammonium benzoate and ammonium adipate that the oxidative destruction of the corresponding carboxylate anion is involved in a rate determining step of the process. V. I. Vernadskii Institute of General and Inorganic Chemistry, Ukraine Academy of Sciences, 32/34 Academician Palladin Prosp., 252680 Kiev-142, Ukraine. Translated from Teoreticheskiya i éksperimental’naya Khimii, Vol. 33, No. 1, pp. 58–61, January–February, 1997.     

Principal relationships of the heterogeneous catalytic oxidation of benzene and its derivatives

The results of investigations into the processes involved in the heterogeneous catalytic oxidation of benzene and its derivatives at the L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, are summarized. The mechanisms of the full and partial oxidation of benzene, toluene, and their halogen derivatives are discussed. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, Kiev. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 3, pp. 133–147, May–June, 1998.     

Mechanisms of the coupling of one-and two-electron reactions in chemical and biochemical processes

The mechanisms of chemical and biochemical reactions in which one-electron stages ae coupled with two-electron stages are examined. The mechanisms of the coupling of the one- and two-electron stages in the electron-transport systems of the living cell are discussed on the basis of an analysis of chemical models. Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine, 1 Murmanskaya ul., Kiev 253094, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 3, pp. 133–144, May–June, 1999.     

Quantity of sorbed ions and forms of their binding to carbon surface as factors influencing catalytic activity in esterification and hydrolysis reactions

Results are summarized and correlated from studies of how the quantity and nature of sorbed ions and the forms of their binding with the surface of carbon materials (CM) differing in structure and origin will influence the catalytic activity in acid-type reactions. It has been shown that of all of the methods of incorporating metals into the CM surface, the most effective is the ion-exchange modification. It is suggested that the mechanisms of catalysis of protolytic reactions by various ion-exchanged forms of CM are all quite similar. “Sonar” Scientific and Engineering-Technological Center of Biotechnical Systems, National Academy of Sciences of Ukraine, 52/2 Victory Prospect, Kiev 252057, Ukraine. Affiliation of second author: Institute of Sorption and Problems in Endoecology, National Academy of Sciences of Ukraine, 32/34 Academician Palladin Prospect, Kiev-142 252680, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 3, pp. 175–179, May–June, 1997.     

Effect of the nature of the metal oxide on selective transformation of methane under unsteady conditions in the absence of oxidant in the gaseous phase

The catalytic transformation of methane into higher hydrocarbons was studied under unsteady conditions on oxides of various metals (Pb, Fe, Nb, Ti, Cd, Mo, Mg, Zn, Zr, Bi, Mn), and also on Sr-, La-, Y-, and Mn-containing oxides of perovskite structure. It is shown that the effectiveness of the catalysts not only depends on their chemical composition, but also is determined to a considerable degree by the specific surface of the oxides. L. V. Pisarzhevskii Institute of Physical Chemistry, Academy of Sciences of Ukraine, 252039 Kiev, Prosp. Nauki, 31, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 2, pp. 91–95, March–April, 1997.     

Methane esterification in oleum

The reactions taking place during methane esterification in oleum were investigated. It was found that the primary products were methyl bisulphate and formaldehyde, which was subsequently oxidized to carbon dioxide. The catalyst, Pd or PtCl₄, was needed to activate methane and for its oxidation to the primary products. The formation of CO₂ was not a catalytic process. It was found that the addition of either carbon dioxide or ester into the reaction mixture did not slow down the reactions. Methane oxidation in oleum is an irreversible process, during which water is produced and subsequently consumed to give sulphuric acid by the reaction with sulphur trioxide. Presented at the 33rd International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 22–26 May 2006.     

CO_2选择氧化低碳烷烃的研究进展

本文以低碳烷烃的选择催化氧化反应为对象 ,对几种 CO2 选择氧化低碳烷烃的反应工艺进行了归纳总结 ,重点分析讨论了催化氧化反应中 CO2 作为氧化剂的作用机制 ,并提出了研究展望。     

Kinetics of nonstationary condensation of methane on a perovskite catalyst

The interaction of methane with the oxidized surface of the KNaSrCoO_3−x is first order in methane with respect to formation of higher hydrocarbons and zero order with respect to formation of CO₂. At the initial stage the rate of formation of the reaction products is independent of the amount of oxygen from the catalyst consumed (up to 5–7 monolayers of oxygen), after which the rate of the reaction falls linearly. The overall amount of oxygen consumed in the reaction reaches 30 monolayers. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 03039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 3, pp. 182–187, May–June, 2000.     

Design of supramolecular metal complex catalytic systems for petrochemical and organic synthesis

Specific features of the behavior of the supramolecular metal complex catalysts based on calixarenes, cyclodextrins, and dendrimers in the reactions of hydroformylation, Wacker oxidation, hydroxylation of aromatics, 2-naphthol coupling, and oxidative coupling of styrenes and benzene were studied. The factors affecting the catalytic activity and selectivity are discussed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 766–778, April, 2008.     

CO2选择氧化低碳烷烃的研究进展

本文以低碳烷烃的选择催化氧化反应为对象，对几种CO₂选择氧化低碳烷烃的反应工艺进行了归纳总结，重点分析讨论了催化氧化反应中CO₂作为氧化剂的作用机制，并提出了研究展望。     

Activation and oxidation of carbon-based materials impregnated with potassium carbonate

Details are considered on the porous structure and oxidation of activated carbon-fiber tissue and anthracite in the presence of potassium carbonate. Specimens impregnated with K₂CO₃ show those processes of structuring and oxidation substantially accelerated. The time and temperature parameters required to produce highly porous sorbents and cation exchangers based on these carbon materials are much lower than those for the usual activation-oxidation process involving atmospheric oxygen. Institute for Sorption and Endoecology, National Academy of Sciences of Ukraine, 13 ul. Generala Naumova, Kiev 252164, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 5, pp. 306–310, September–October, 1999.     

Reactivity of La1 ? xSrxFeO3 ? y (x = 0–1) Perovskites in Oxidation Reactions

Oxygen species and their reactivity in La_{1 − x} Sr _x FeO_{3 − y} perovskites prepared using mechanochemical activation were studied by temperature-programmed reduction (TPR) with hydrogen and methane. The experimental data were compared with data on the catalytic activity in oxidation reactions. It was found that the rates of CO and methane oxidation on the perovskites in the presence of gas-phase oxygen correlated (k = 0.8) with the amount of reactive surface oxygen species that were removed by TPR with hydrogen up to 250°C. Maximum amounts of this oxygen species were released from two-phase samples (x = 0.3, 0.4, and 0.8), which exhibited an enhanced activity in the reaction of CO oxidation. In the absence of oxygen in the gas phase, methane is oxidized by lattice oxygen. In this case, the process activity and selectivity depend on the mobility of lattice oxygen, which is determined by the temperature, the degree of substitution, the degree of reduction, and the microstructure of the oxide. Thus, the high mobility of oxygen, which is reached at high concentrations of point defects or interphase/domain boundaries, is of importance for the process of deep oxidation. However, the process of partial oxidation occurs in single-phase samples at low degrees of substitution (x = 0.1–0.2). __________ Translated from Kinetika i Kataliz, Vol. 46, No. 5, 2005, pp. 773–779. Original Russian Text Copyright ? 2005 by Isupova, Yakovleva, Alikina, Rogov, Sadykov.     

Kinetics of the oxidative coupling of methane in the presence of model catalysts

The kinetics of the oxidative coupling of methane (OCM) in the presence of La/MgO and NaWMn/SiO₂ catalysts in a flow reactor at low reactant conversions was studied. It was found that, in spite of different compositions and properties of the test catalysts, the formation of ethane from methane and ethylene from ethane can be described within the framework of the Mars-van Krevelen redox model in both cases. The rate laws of side reactions, which lead to the formation of carbon oxides, are different from the rate laws of the target reactions of the conversion of methane into ethane and ethane into ethylene. The kinetic parameters required for the numerical simulation of the OCM process were determined for either of the catalysts.     

Energetics of electron processes in semiconductor photocatalytic systems

The energetics of electron processes in photocatalytic systems based on dispersed semiconductors, their nanocomposites and heterostructures are examined. Methods for the approximate estimation and quantitative determination of their energetic characteristics are evaluated and energy diagrams of photocatalytic systems based on semiconductor nanocomposites and their heterostructures are plotted. Analysis of the diagrams permits the elucidation of the nature of their photocatalytic effects in redox reactions. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 03039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 2, pp. 69–89, March–April, 2000.     

Mechanism of reactions of photocatalytic synthesis of chlorohydrins

A mechanism of photocatalytic synthesis of chlorohydrins from olefins and peroxo complexes of titanium (IV) is proposed. It consists of formation of radical-containing complexes, their reactions with olefins, and decomposition of the α-oxides obtained by hydrogen chlorides. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prosp. Nauki, 252039 Kiev, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 1, pp. 17–21, January–February, 1997.     

Quantum-chemical investigation of the mechanism of nucleophilic addition of Cl− to the triple bond of methyl acetylenedicarboxylate

A quantum-chemical investigation of the mechanism of the nucleophilic oxidative addition of Cl⁻ to methyl acetylenedicarboxylate was undertaken by the MNDO-PM3 method. Each stage of the two-stage mechanism involves the addition of Cl⁻ to the carbon-carbon multiple bond of the substrate with subsequent one-electron oxidation of the intermediates. Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Kiev. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 3, pp. 133–135, May–June, 1997.