Peculiarities of the formation of catalysts, based on γ-Al2O3 modified with Ca2+ and Ni2+ ions, highly active and resistant to carbonization in dry reforming of methane into syngas reaction: relationship between physical-chemical and catalytic proper

Ni x Ca 1-x Al 2 O 4 samples, where x = 0.1-0.5, were obtained by co-precipitation followed by drying on air at room temperature. After calcination in air at 700 °C, an oxide compound with a defective structure g-Al 2 O 3 , in which Ni 2+ and Ca 2+ ions are stabilized, as well as highly dispersed fragments of NiAl 2 O 4 and NiO was formed. After pretreatment stage (reducing in H 2 -containing mixture) and work in the reaction medium, nickel is partially reduced to the metallic state and leaves the structure of the compound, forming on the surface highly dispersed Ni 0 particles with a size of 3–15 nm. Calcium is stabilized in the structure of g-Al 2 O 3 and on its surface. The introduction by Ca 2+ leads to a significant increase in the concentration of not very stable surface and bulk carbonates and bicarbonates, which promotes the oxidation of C-containing intermediate compounds formed on Ni 0 centers. In addition, the modification of Ca 2+ leads to decrease the concentration of strong acid sites on the surface, the formation of a weaker CO 2 bond under reaction conditions, and the fool disappearance of signals from CO complexes with strong LAC, which significantly reduces the amount of carbon, which is formed at the stage of deposition on the surface. The resulting catalysts are characterized by high activity and stable work for a long time in the dry reforming methane reaction.