V. Yu. Bychkov

Oxidative coupling of methane with participation of oxide catalyst lattice oxygen

Abstract Redox properties of the supported Li 2 O/MgO, K 2 O/Al 2 O 3 and PbO/Al 2 O 3 catalysts are studied. New mechanism of the catalyst re-oxidation is suggested. Re-oxidation of the catalyst in the course of steady-state reaction can proceed as an oxidative dehydrogenation of surface OH groups.

The nature of the active phase in supported neodymium catalysts for oxidative coupling of methane

Abstract Catalytic properties of supported neodymium oxide in oxidalive coupling of methane were studied. The most efficient catalysts contain NdzO3 as separated phase. The efficiency increases with the rise of oxidative sites concentration in catalyst

The Study of Self-Oscillations During CH 4 Oxidation Over Ni by the Pulse Method: Is it Possible?

For the first time, the pulse method has been applied to the study of the self-oscillatory behaviour. For methane oxidation over Ni foil the response to a sequence of equal pulses has been strictly periodic. The pulse method allowed to obtain some new information about the origin of oscillations in this reaction.Graphical Abstract

Synchronization of Local Oscillators in Oxidation Reactions of C 1 -C 4 Hydrocarbons over Metal Catalysts

The synchronization of reaction rate oscillations in the oxidation of C1–C4 hydrocarbons over polycrystalline nickel, cobalt, and palladium foils has been investigated. The synchronization of foil temperature oscillations during the reaction takes place via the diffusion of the reactants in the gas phase. For the nickel catalysts, the synchronization of the oscillators occurs in the same phase, while for the palladium catalysts, both in-phase and antiphase oscillations are observed. This distinction between the dynamic behaviors of the systems of two coupled oscillators is due to the fact that the mechanism of reaction rate oscillations varies from one metal to another.

Ethylene oxidation under conditions of the oxidative coupling of methane

Ethylene conversion under conditions of the oxidative coupling of methane has been investigated. In an empty reactor above 740°C, ethylene oxidation occurs at a higher rate and its main product is carbon monoxide. Filling the reactor with an inert material (quartz) or a NaWMn/SiO2 catalyst leads to a marked decrease in the ethylene conversion rate. Addition of methane to the reaction mixture dramatically slows down ethylene conversion rate and increases the C3 hydrocarbon content of the reaction products. The kinetics of ethylene oxidation in the presence of methane over the NaWMn/SiO2 catalyst is reported.

Self-Sustained Oscillations as a Method to Increase an Active Surface and Catalytic Activity of Ni and Pd

The effect of Ni and Pd surface development during catalytic self-oscillatory oxidation of C1–C4 alkanes on the activity of these two metals in other catalytic reactions was studied. Scanning electron microscopy investigations revealed that the surface of bulk Ni and Pd (foil or powder) developed significantly faster during alkane oxidation in a self-oscillatory regime than under stationary conditions. Thanks to increase in available metal surface achieved during such self-oscillatory pretreatment, catalytic activity of Ni in methane dry reforming and in ethylene hydrogenation and that of Pd in total methane oxidation increased by an order of magnitude compared to the untreated metals. With time on stream, the activity dropped to some stationary level that was still significantly higher than the activity of the fresh metals. Morphological changes of Ni during the pretreatment were caused by periodic oxidation–reduction of the surface atomic layers whereas in case of Pd redox cycles were accompanied by carbon dissolution-removal. The amount of carbon dissolved in Pd during self-oscillatory oxidation of C1–C4 alkanes decreased with increasing chain length, likewise the metal surface development. Supported Pd/Al2O3 catalyst did not exhibit significant activity changes after the self-oscillatory pretreatment suggesting that the morphology of Pd particles remained unaltered.Graphical Abstract