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The partial oxidation of isobutylene to methacrolein on a multicomponent multiphase Co-Mo-Bi-Fe-Sb-K-O catalyst and on catalysts from which some components were absent was studied. Activity and selectivity changes in the case of isobutylene oxidation were the same as in the oxidation of propylene; however, the rate of propylene oxidation was higher than that of isobutylene oxidation. The X-ray diffraction analysis of the catalysts before and after the reaction indicated the occurrence of a number of phases in the samples: α-CoMoO4, β-CoMoO4, Fe2(MoO4)3, reduced bismuth molybdate species, MoO3, and reduced MoO x species. Under catalytic reaction conditions, redox phase transformations occurred. Iron molybdate and molybdenum oxide phases underwent the largest transformations. Of two molybdenum oxide phases, a β-Mo4O11 phase with a structure of a crystallographic shift is formed in the course of catalysis, whereas the second phase (MoO3) almost does not participate in catalysis and occurs in an excess.

The role of various components of a multiphase oxide catalytic system in the partial oxidation of propylene to acrolein is investigated. Catalytic activity is studied for the Co6–8Mo12Fe2–3Bi0.5–0.75Sb0.1K0.1Ox catalyst, which is taken to be the reference, and for catalysts in which the amount of some component is progressively reduced down to zero. The results obtained provide insights into the role of the components of the catalyst.CoMoO4 forms the structural framework of the catalyst. Iron molybdate can be stabilized on CoMoO4 as β-phase. As its content is increased, the catalyst gains activity but its selectivity declines. Bismuth molybdate is responsible for the selectivity of the process. When present in small amounts, MoO3 raises the selectivity, binds free oxides, and converts reduced molybdates into their oxidized forms. Excess molybdenum trioxide causes a dramatic fall in the catalytic activity. Potassium and antimony decrease the catalytic activity, but even small amounts of these elements raise the selectivity of the catalyst. Chromium can substitute for iron atoms in the multicomponent catalyst. Ni, Mn, and Mg substitute for Fe in iron molybdate to decrease the catalytic activity.

The structures of a complex multicomponent Co-Mo-Fe-Bi-K-Sb-O catalyst for the oxidation of propylene to acrolein and simpler catalysts from which some catalyst components were absent were studied by X-ray diffraction analysis. The phases of α-CoMoO4, β-CoMoO4, Fe2(MoO4)3, Bi2O3 ⋅ MoO3, Bi2O3 ⋅ 2MoO3, Bi2O3 ⋅ 3MoO3, oxidized molybdenum oxide, and reduced molybdenum oxide are the main components of the catalyst. Ternary compounds were not detected. Under catalytic reaction conditions, the relative amounts of the phases changed; this change suggests the occurrence of redox transformations with the participation of these phases, probably, at the interface.

Cobalt- and iron-containing catalysts supported on MgO, ZrO2, γ-, θ-, and α-Al2O3 were synthesized and studied in the CO2 reforming of methane. The CoO/α-Al2O3 systems are the most active and stable. The dependence of the catalytic activity and the degree of reduction on the amount of supported CoO was studied. In the active catalysts, CoO is weakly bound to the support and can readily be reduced to metal cobalt. Coke formed in the course of the reaction does not affect the activity of the CoO/α-Al2O3 catalyst.

The interactions of oxidized and reduced Co/α-Al2O3 (4 wt % CoO) with H2, CH4, CO2, and O2 and their mixtures are studied in flow and pulse regimes using a setup involving a DSC-111 differential scanning calorimeter and a system for chromatographic analyses. It is shown that treatment with hydrogen at 700°C results in the partial reduction of cobalt oxide to Co. Methane poorly reacts with the oxidized catalyst but readily reacts with the reduced catalyst to form H2 and surface carbon. The initial surface carbon transforms into other forms, which block the cobalt surface to different extents and differ in the heats of reaction with CO2. Carbon dioxide may react with the surface carbon to form CO (rapidly) and with metallic Co to form CO and CoO (slowly). Thus, the main route of methane reforming with carbon dioxide on Co/α-Al2O3 is the dissociative adsorption of CH4 to form surface carbon and H2 and the reaction of surface carbon with CO2 to form CO via the reverse Boudouard reaction.

The reactions of oxidized and reduced 6 wt % NiO/α-Al2O3 with H2, CH4, CO2, O2, and their mixtures are studied in flow and pulse regimes using a setup equipped with a differential scanning calorimeter DSC-111 and a system for chromatographic analysis. It is shown that treatment with hydrogen at 700°С results in the partial reduction of NiO to Ni. Methane practically does not react with oxidized Ni/α-Al2O3 but it does react actively with the reduced catalyst to form H2 and surface carbon. The latter is capable of reacting with lattice oxygen of Ni/α-Al2O3 (slowly) and with adsorbed oxygen (rapidly). Carbon dioxide also reacts with surface carbon to form CO (rapidly) and with metallic Ni to yield CO and NiO (slowly). Thus, the main route of methane reforming with carbon dioxide on Ni/α-Al2O3 is the dissociative adsorption of CH4 to form surface carbon and H2 and the reaction of this carbon with CO2 resulting in the formation of CO by the reverse Boudouard reaction. Side routes are the interaction of the products of methane chemisorption with catalyst oxygen and the dissociative adsorption of CO2 on metallic nickel. A competitive reaction of surface carbon with adsorbed oxygen results in a decrease in the CO2 conversion in methane reforming with carbon dioxide. Therefore, the presence of gaseous oxygen in the reacting mixture decelerates methane reforming (catalyst poisoning by oxygen).

Published data on the molar absorption coefficients e and integral intensities A 0 of vibrations in physically and chemically adsorbed molecules are reviewed. Analysis of published data shows that bonds characterized by high values of the dipole momentum derivative with respect to the normal coordinate change during adsorption toward decreasing this derivative, whereas bonds characterized by a low value of the derivative change toward increasing the derivative. Thus, adsorption results in a decrease in the difference in values of the dipole momentum derivative with respect to the normal coordinate of different bonds compared with the same bonds in the individual molecules. In addition, the interval of changing the molar absorption coefficients for the surface complexes are at least two orders of magnitude lower than that for the same bonds in the molecules in the gas phase. A series for the degree of easiness in detecting complexes on the catalyst surface (the series of decreasing the molar absorption coefficient) is proposed.

This paper presents an overview of the plenary lectures and some of the oral and poster presentations at the 4th International Congress on Oxidation Catalysis in Potsdam (Germany). The main topics were the partial oxidation of alkanes and the oxidation of olefins by H2O2. Considerable attention is given to the use of modern physical methods in the mechanistic studies of oxidation catalysis and in the studies of catalyst structures.

Advantages and drawbacks of commercial catalysts for gas-phase hydrogenation are considered. The use of modified catalysts, including nickel catalysts modified with heteropoly compounds, is promising. Data on the selective reduction of carbonyl compounds and hydrogenation of aromatic hydrocarbons over these catalysts are presented. Palladium films are shown to be the best catalysts for the selective reduction of acetylene compounds to olefins.

The catalytic activity, adsorption capacity, and pore structure of low-percentage nickel catalysts supported on γ-Al2O3or activated carbon and modified by tungsten heteropoly compounds are studied. The activity, selectivity, and thermal stability of the catalysts in the vapor-phase hydrogenation of olefins and aromatic hydrocarbons are higher than those for conventional nickel catalysts. The concentration of nickel in the catalysts is 10–15 times lower than that in commercial catalysts. However, the modified catalysts have higher specific surface areas of metal, higher dispersion, a uniform distribution of metal particles, and a pore-radius distribution other than in the support. The study of water adsorption and desorption showed that the heteropoly compound modifying the γ-Al2O3support covers the support surface completely, and supported nickel interacts with the active surface of the modifying agent rather than with Al2O3. A hydrogenation mechanism is proposed, which involves H2dissociation on Ni particles and the subsequent diffusion of hydrogen atoms via a spillover mechanism to the adsorbed organic compound with the participation of the OH groups of the modifying agent.

Temperature-programmed reduction by hydrogen, temperature-programmed desorption of O2, local X-ray spectral analysis, and scanning electron microscopy are used to study redox processes occurring on the Ni–Cr2O3/MgO and Ni/MgO catalysts for carbon dioxide reforming of methane. The reduction of Ni/MgO leads to the formation of nickel clusters distributed over the surface of MgO. During the reduction of NiO–Cr2O3/MgO, chromates are transformed into chromites, and then nickel is formed by the reduction of spinel NiCr2O4. Reoxidation leads to the oxidized structures NiO, NiCr2O4, and NiCrO4.

The results of a study of the reactions catalyzed by nontraditional fiberglass woven catalysts activated by metals or oxides, are presented. The catalytic activity of such catalysts, activated by implanting Pt, Pd, Co, or Cr, in NO reduction with carbon monoxide and propane is studied. Fiberglass catalysts containing Pt and Pd are more active than traditional catalysts. The catalysts are studied by temperature-programmed reduction (TPR), IR spectroscopy, and diffuse-reflectance electronic spectroscopy. Active sites of two kinds act on the platinum catalysts. One of them is platinum encapsulated in the glass matrix of the support. Active sites are assumed to be at the metal-support interface