Melt-assisted phase transformations of A/W/Mn/SiO2 (A = Li, Na, K, Rb, Cs) composite catalysts

Abstract

This paper analyzes results obtained in studies of A/W/Mn/SiO₂ (A = Li, Na, K, Rb, Cs) composite catalysts for the oxidative coupling of methane (OCM). Particular attention is paid to phase transformations. It is pointed out that the SiO₂ matrix is an active catalytic component of the composites, rather than an inert carrier of additives, and that the heterogeneous OCM process involves melts based on alkali metal tungstates, along with polycrystalline manganese oxides. The effects of the cation ratio and synthesis method on the phase composition of the A/W/Mn/SiO₂ (A = Li, Na, K, Rb, Cs) materials is examined.