Metastable Bi2O3 : GeO2 and Bi2O3 : SiO2 Bismuth-Containing Catalysts for Oxidative Dimerization of Methane

We have studied how the initial state of polycrystals of the metastable compounds Bi2GeO5 and Bi2SiO5 with an Aurivillius-type structure and a glass phase with the equimolar composition Bi2O3 : SiO2 influences the performance of in situ forming catalysts for oxidative dimerization of methane (ODM). The results confirm the effect of the gas phase consisting of the starting components of the catalyzed reaction on improvement of the performance of the catalyst obtained upon thermal decomposition of its initial metastable state: in situ catalyst "self-adjustment" effect. The best catalytic properties for ODM reaction are offered by bismuth silicate (Bi2SiO5) decomposition products, and the highest activity is exhibited by the catalyst forming upon crystallization of the glass phase. Bismuth-containing oxide catalysts have been shown to have the best properties if high-purity starting reagents are used to synthesize them.