Studies on activation factors for oxidative coupling of methane over lithium-based silicate/germanate catalysts

Abstract

Several oxides containing group 14 elements were characterized to investigate catalytic activity factors and the reaction mechanism for oxidative coupling of methane (OCM). Lithium-based silicate Li2SiO3 and germanate Li2GeO3 showed much higher selectivities for C2 hydrocarbons than their Sn-based counterpart Li2SnO3. Our XPS study suggested that strong metal–oxygen bonds in silicates and germanates could be of importance to effectively suppress the deep oxidation of methane at the catalyst surface, resulting in enhanced C2 selectivities. In contrast, weakly bound surface oxygen of Sn-based oxides is subject to direct oxygenation of methane to form COx as by-products, emphasizing the importance of metal–oxygen bonding strength. To achieve high OCM catalytic activity, effective methane activation by strong basicity is also required, and the local environment around oxygen sites could be a key factor to enhance CH4 conversion. Based on the chemical/structural viewpoints, we found that silicate and germanate with higher Li contents, Li4SiO4 and Li4GeO4, are significantly OCM active, comparable to the previously reported catalyst Li2CaSiO4.

Graphical abstract: Studies on activation factors for oxidative coupling of methane over lithium-based silicate/germanate catalysts

Supplementary files

Article information

Article type
Paper
Submitted
09 Sep 2021
Accepted
22 Oct 2021
First published
22 Oct 2021

Catal. Sci. Technol., 2021, Advance Article

Studies on activation factors for oxidative coupling of methane over lithium-based silicate/germanate catalysts

T. Matsumoto, S. Ishikawa, M. Saito, W. Ueda and T. Motohashi, Catal. Sci. Technol., 2021, Advance Article , DOI: 10.1039/D1CY01641E

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