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In order to establish the formation patterns of the Co–Mg oxide system, samples with different Co:Mg ratios and heat treatment temperatures were synthesized and studied. A study of the samples confirmed the phase transition of MgxCo2–xO4 spinels into the corresponding solid solutions at 800–900 °C. The similarity of the formation patterns for different compositions is shown. The rocksalt oxide in low-temperature samples is an anion-modified paracrystalline phase that forms a "true" solid solution only upon spinel decomposition. The TPR profiles of the decomposed Co3O4 spinel show surface Co3O4 peaks and a wide peak corresponding to the well-crystallized CoO, while partial Co3O4 TPR up to 380 °C results in dispersed and amorphous CoO. The high-temperature non-stoichiometric samples are poorly reduced, indicating their low oxygen reactivity. Spinel reoxidation after heat treatment to 1100 °C by calcination at 750 °C showed complete regeneration for MgCo2O4–Co3O4 samples and its absence in case of an excess of MgO relative to stoichiometry. [ABSTRACT FROM AUTHOR]

Co–Mg catalysts for methane combustion were synthesized and studied, revealing the transformation of MgCo2O4 spinel into a CoO–MgO solid solution with oxygen release from the spinel lattice as the calcination temperature increased. Repeated heat treatment of the calcined solid solution at lower temperatures led to spinel regeneration with segregation of the solid solution phase. A TPR of the samples showed the presence of two characteristic peaks, the first of which relates to the transition of Co3+Oh spinel to the Co2+Oh structure of CoO, and the second to the reduction of CoO to Co°. The second peak was observed at 540–620 °C for samples calcined at temperatures below spinel decomposition, and for high-temperature samples at 900–1100 °C. Taking into account the identity of the structure of phases obtained in both cases, the formation of not a true CoO–MgO solid solution, but rather a mixture of ordered oxides ("pseudo-solid solution") in the low-temperature region, was postulated. A study of the activity of the samples showed the high activity of the spinel systems and a linear relationship between the activation energy of methane oxidation and the heat treatment temperature. [ABSTRACT FROM AUTHOR]

The purpose of this work is to study the influence of thermal effect on the surface morphology of the Fe–Cr–Al (Kh15Yu5) alloy foil and the elemental composition of the surface layers. Also, studies have been carried out on the physicochemical characteristics of the primary support with the deposited secondary support in the initial state and within the temperature range from 25 to 900 °C. The research was carried out on a JSM 6610 LV, JEOL scanning electron microscope with an installed INCA Energy 450 energy-dispersive microanalysis system. Before depositing secondary support (aluminum oxide), for a stronger adhesion to the foil metal, the foil surface was pretreated with a phosphating solution. It was found that during heating up the elemental composition of the surface layer of the Kh15Yu5-alloy foil does not remain constant and depends on the mode of thermal effect. This implies the possibility of changing the adhesion and adsorption properties of the foil surface, as well as the need to take this into account when depositing secondary support and an active phase to the foil. Studies have shown that the applied methods for phosphatizing and depositing secondary support to the foil surface make it possible to obtain a quite resistant coating. No peeling of the secondary support from the foil surface is observed during high-temperature treatment in the air. [ABSTRACT FROM AUTHOR]

The catalytically active vanadium-containing system of γ-Al2O3 was studied using a wide range of physical and chemical methods, depending on the synthesis conditions. It is shown that the vanadium-containing system includes several complexes with different thermal stabilities and catalytic activities. Low-active complexes are destroyed with the formation of more active ones based on V2O5 oxide, as the temperature of heat treatment increases. It can be assumed that V2O5 oxide has the decisive role in its catalytic activity. It was concluded that the vanadium-containing catalytic system on aluminium oxide, in the studied temperature range, is thermally stable and shows high activity not only in the reduction of nitrogen oxides but also in the oxidation of hydrocarbons (even of the most difficult ones, such as oxidizable methane). These properties of the system make it quite promising in the field of application for the purification of the exhaust gases of motor transport and industrial enterprises with environmentally harmful components, as well as for understanding the mechanism of the action of the catalysts in these processes, which is very important for solving the problems of decarbonization and achieving carbon neutrality. [ABSTRACT FROM AUTHOR]