Selective oxidation of methane to methanol is challenging due to the propensity to easily form overoxidation products like carbon monoxide (CO) or carbon dioxide (CO2). Recent experimental and theoretical work indicate that over-oxidation is prevented in copper-exchanged zeolites by stabilization of the methoxy groups at the Bronsted acid sites. We here use density functional theory (DFT) calculations to investigate the interactions of the separated methyl group (from methane C-H activation) with framework aluminate tetrahedra in Cu-exchanged zeolite mordenite. We discuss the possibilities of tuning this interaction as a means to optimizing the scavenging of the separated methyl by the Bronsted acid sites. Trends in the binding energies are compared to the impact of the aluminate tetrahedra on the C-H activation energies by [Cu2O]2+ active sites. We provide prescriptions on approaches to further lower the overoxidation products during methane-to-methanol conversion in Cu-exchanged zeolite mordenite.

Methane C-H activation: Computational investigation of methyl interactions with zeolite framework aluminate tetrahedra

ACS Fall 2021

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