N. V. Pavlenko

Investigation of the mechanism of methane formation in the fischer-tropsch synthesis on a Co/SiO2·ZrIV catalyst

Methane is formed in the Fischer-Tropsch synthesis under real conditions both through intermediates leading to chain propagation and by hydrogenation of surface carbon.

Kinetic and mechanistic features of carbon monoxide hydrogenation over supported transition metals

Data on the kinetics and mechanism of carbon monoxide hydrogenation to form alkanes, alkenes, and alcohols over supported transition metals are summarized and correlated. The observed kinetics of the overall carbon monoxide conversion can be interpreted on the basis of a mechanism that includes equilibrium adsorption of CO in the molecular form and equilibrium dissociative adsorption of hydrogen. Detailed mechanistic schemes and the corresponding kinetic models are presented for the reactions of formation of alkanes, alkanes, and alcohols. Catalytic activity and selectivity are examined in relation to the adsorptive and physicochemical properties of the catalysts.

Influence of electronic state of rhodium in supported bimetallic catalysts on catalytic activity and selectivity in carbon monoxide hydrogenation reactions

Data on the mechanism and kinetics of the hydrogenation of carbon monoxide to saturated hydrocarbons and alcohols over supported bimetallic rhodium-containing catalysts are summarized and correlated. Rankings of specific catalytic activity and selectivity of Rh-M′/Al2O3 catalysts in relation to the chemical nature of M′, and hence in relation to the electronic state of the rhodium, are interpreted from a common point of view. On the basis of the interrelations that were found between the physicochemical and catalytic properties of these bimetallic systems, ground rules were formulated for selecting monotypical catalysts for the selective hydrogenation of carbon monoxide.

Mechanism and kinetics of carbon monoxide hydrogenation over supported bimetallic rhodium catalysts to form saturated hydrocarbons

Experimental kinetic and adsorption data have been used to elucidate the mechanism of formation of methane, ethane, and propane from carbon monoxide over supported Rh-M′/Al2O3 bimetallic catalysts. A kinetic model based on the proposed mechanism gives a quantitative description of the experimental data.

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.

Catalytic properties of the carbides of transition metals in oxidation reactions

It was shown that the carbides of transition metals are effective catalysts of oxidation reactions on account of their metal-like nature, combined with their high chemical and thermal stability. The results from systematic investigations into the catalytic characteristics of the carbides in the oxidation of hydrogen, carbon monoxide, and ammonia and in the oxidative coupling of methane (OCM) are examined. The first two reactions are total oxidation processes, and the oxidation of ammonia is a selective oxidation process. The oxidative coupling of methane is a heterogeneous-homogeneous process and represents a prospective method for the direct transformation of methane into higher hydrocarbons.

Effect of Alkali Metals on the Strength of Oxygen–Catalyst Bond in Co-Containing Perovskites

Modification of the perovskite SrCoO3 with alkali metal atoms has a considerable influence on the strength of the oxygen–catalyst bond and causes an increase in the weakly bonded oxygen in the modified samples. An approximate correlation has been established between the reactivity of the oxygen in the perovskite and its catalytic activity in the non-stationary condensation of methane to higher hydrocarbons.

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.

Mechanism and kinetics of the hydrogenation of CO with the formation of paraffins and olefins on an iron catalyst

A kinetic model is proposed for the hydrogenation of CO on a Fe/Al2O3 catalyst, based on a mechanism of parallel formation of paraffins and olefins. The model satisfactorily describes the experimental data on the dependence of the total rate of conversion of CO to hydrocarbons and the selectivity with respect to paraffins on the composition of the reaction mixture. It was shown that in the case of olefins the successive steps of their hydrogenation, which make a substantial contribution to the distribution of reaction products, must be taken into consideration.

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.