L. N. Raevskaya

Influence of conjugate reoxidation of the surface on the oxidation kinetics of alkylaromatic compounds over V2O5 and V2O5−TiO2 catalysts

Kinetics of low-temperature oxidation of toluene and its derivatives over V2O5 and V2O−TiO2 has been studied in a differential flow reactor. According to the response method, complete oxidation follows the mechanism of conjugate reoxidation of the surface. A kinetic model for this process is suggested.AbstractВ проточном дифференциальном реакторе изучена кинетика инзкотемпера-турного окисления толуола и его производных на V2O5 и V2O5−TiO2. Методом отклика показано, что глубокое окисление идет по механизму сопряженного реокисяения поверхности. Дана кинетическая модель процесса.

Effect of the Vanadium Content in V2O5/SiO2 Catalysts on Their Activity and Selectivity in the Partial Oxidation of Methane

The effect of the vanadium content on the catalytic characteristics of samples of V2O5/SiO2, prepared by molecular layering, was investigated. It was shown that in the region of relatively small vanadium contents in the catalyst its surface concentration does not affect the selectivity of the process. The obtained relation between the initial selectivity and the relative reactivity of formaldehyde and the surface density of oxide-vanadium groups in the deposited catalyst is discussed.

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.

Kinetics of nonstationary condensation of methane on a perovskite catalyst

The interaction of methane with the oxidized surface of the KNaSrCoO3−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.

A kinetic model of the oxidation of aromatic compounds on oxide catalysts

We obtained experimental data on the oxidation of toluene in a differential flow-through reactor (the degree of conversion of toluene did not exceed 7.5%) at atmospheric pressure, temperatures of 523-583~ and rate of flow of the reaction mixture 2.5 �9 10 -3 liter/sec. The weight of the catalyst sample was 1.5 g, grain size 0.5-1 mm, specific surface 5.5 m2/g. An analysis of the reaction mixture was performed chromatographica lly; samples for analysis of the organic components were introduced with the aid of a thermostatically controlled six-way metallic stopcock. The experimental data obtained are cited in Figs. 1 and 2. The mechanism of the ox_idation of toluene at low degrees of conversion can be represented by the scheme

Effect of CH4/Air Ratio on Selectivity of Partial Oxidation of Methane on V2O5/SiO2 Catalyst

We have studied partial oxidation of methane on V2O5/SiO2 (0.8 mass % V) in a flow-through catalytic fixed-bed reactor. We found that the methane/air ratio in the starting reaction mixture has practically no effect on the selectivity of the process. The dependence of the selectivity on the methane conversion can be described by a model with such reaction parameters as the initial selectivity and the relative reactivity (with respect to methane) of the reaction products.

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.