Larisa G. Pinaeva

The kinetics of the formation of methane condensation products in the absence of oxygen at 600°C was studied on 1% Pt/γ-Al₂O₃ and 1% Pt/MgAlO_x samples with similar platinum cluster sizes. In contrast to the reference sample 1% Pt/γ-Al₂O₃, removal of strongly adsorbed carbon-containing compounds accumulated during the reaction by oxidation at the same temperature completely restored the catalytic characteristics of 1% Pt/MgAlO_x systems. The possibility of increasing the operation time of such catalysts in a cyclic mode with maximum productivity in terms of C₂–C₃-hydrocarbons and minimal formation of CO and CO₂ at the regeneration stage was demonstrated.

MeO_x/CeO₂ (Me = Fe, Co, Ni) samples were tested in an ¹⁸O₂ temperature-programmed isotope exchange and N₂O decomposition (deN₂O). A decrease in the rate of deN₂O in the presence of oxygen evidences the competitive adsorption of N₂O and O₂ on the same sites. A study of isotope oxygen exchange revealed dissociative oxygen adsorption with the subsequent formation of surface oxygen species. The same species, more probably, result from N₂O adsorption and the following N₂ evolution to the gas phase. We supposed the same mechanism of O₂ formation from surface oxygen species in both reactions, including the stages responsible for its mobility. A detailed analysis of the kinetics of isotope exchange has been performed, and the rates of one-atom (R^I) and two-atom (R^II) types of exchange were evaluated. The rate of the stage characterizing the mobility of surface oxygen was calculated, supposing the same two-step mechanism was relevant for both types of exchange. The effect of oxygen mobility on the kinetics of deN₂O was estimated. An analysis of the possible pathways of isotope transfer from MeO_x to CeO_x showed that direct oxygen exchange on the Me–Ce interface makes a valuable contribution to the rate of this reaction. The principal role of the Me–Ce interface in deN₂O was confirmed with independent experiments on FeO_x/CeO₂ samples with a different iron content.

CeO₂-Al₂O₃ oxides prepared by co-precipitation (Ce+Al) or CeOx precipitation onto Al₂O₃ (Ce/Al) to obtain dispersed CeO₂ and samples with further supported FeOx (2.5–9.9 weight% in terms of Fe) were characterized by XRD, XPS, DDPA and Raman. Fe/Ce/Al samples with lower surface concentrations of Fe³⁺ were substantially more active in N₂O decomposition at 700–900 °C. It was related to higher oxygen mobility, as estimated from ¹⁶O/¹⁸O exchange experiments and provided by preferential exposing of (Fe-)Ce oxides. Stabilization of some Ce as isolated Ce³⁺ in Fe-Ce-Al mixed oxides dominating in the bulk and surface layers of Fe/(Ce + Al) samples retards the steps responsible for fast additional oxygen transfer to the sites of O₂ desorption.

The level of the main catalysts and industrial technologies for the conversion of natural gas into syngas further convrted into ammonia, methanol, and H₂ was analyzed. The main trends in their development, aimed at reducing the energy and resources consumption, were described including process flowsheets, catalysts, and sorbents at different stages of methane reforming and CO steam reforming.

In the last decade, there was observed a growing demand for both n-butanol as a potential fuel or fuel additive, and propylene as the only raw material for production of alcohol and other more bulky propylene chemical derivatives with faster growing outputs (polymers, propylene oxide, and acrylic acid). The predictable oilfield depletion and the European Green Deal adoption stimulated interest in alternative processes for n-butanol production, especially those involving bio-based materials. Their commercialization will promote additional market penetration of n-butanol for its application as a basic chemical. We analyze briefly the current status of two most advanced bio-based processes, i.e. ethanol–to-n-butanol and acetone–butanol–ethanol (ABE) fermentation. In the second part of the review, studies of n-butanol and ABE conversion to valuable products are considered with an emphasis on the most perspective catalytic systems and variants of the future processes realization.

The main stages of the development of industrial Ag–Al₂O₃catalysts for the gas-phase epoxidation of ethylene are considered. The greatest attention is paid to the methods of preparation aimed at increasing the productivity of the last-generation catalyst systems. The results of the studies of alternative heterogeneous systems based on silicates modified by Ti, Nb, and W for liquid-phase epoxidation of ethylene with H₂O₂ are also summarized. The reasons and methods for solving the problem of their low activity/productivity and stability are analyzed, the directions of increasing the H₂O₂ utilization efficiency are evaluated.

An analysis is performed for the literature data on catalysts used in industrial processes of the conversion of propylene to the most widely used oxygen-containing products: propylene oxide, acrylonitrile, acrolein, and n- and iso-butyraldehydes. The main trends and the prospects for their development are identified. Catalytic systems for promising processes of synthesizing the above products using less expensive propane or alternative oxidants are also considered, and the similarity between their characteristics and values suitable for embarking on their commercialization is determined.

The literature data on the direct catalytic conversion of methane into useful chemical products (Н2, С2+ hydrocarbons, methanol, formaldehyde, and higher oxygenates) were analyzed. Processes based on