Selective methanol formation via CO-assisted direct partial oxidation of methane over copper-containing CHA-type zeolites prepared by one-pot synthesis

Abstract

Direct conversion of methane into methanol at low temperature is a promising process for the efficient utilization of abundant methane as energy and chemical resources, and metal-loaded zeolites have been recently focused as a new candidate catalyst for this reaction. Here, catalytic CO-assisted direct conversion of methane into methanol was demonstrated over Cu-CHA zeolites. Methanol was selectively produced as a solo oxygenate, without the production of C2 oxygenates caused by CO insertion. For the preparation of the Cu-CHA zeolite catalyst, besides the conventional ion-exchange method, a one-pot synthesis approach using a Cu complex as a structure-directing agent was also applied. As both catalysts showed similar activation energies of 29–34 kJ mol⁻¹, the latter one was found to be more feasible resulting in a 1.5 times higher methanol production rate per gram of catalyst. The methanol production rate per Cu atom decreased with the increase of the Cu loading amount, indicating the necessity of low copper loadings for well-dispersed isolated single copper active sites, which would explain the improved result of the one-pot synthesis approach.