Misconceptions and challenges in methane-to-methanol over transition-metal-exchanged zeolites

Abstract

Direct methane functionalization and, in particular, the selective partial oxidation to methanol, remains an eminent challenge and a field of competitive research. The conversion of methane to methanol over transition-metal-containing zeolites using molecular oxygen is a promising and extensively studied process. Herein, we scrutinize some oft-cited assumptions in this topic—which include the labelling of the process as biomimetic, the debate regarding the industrial viability of direct methane-oxidation systems and the claim that methane is difficult to activate—and delineate the extent to which these are scientifically robust. We highlight both the merits and pitfalls of such statements and point out the hazards associated with their improper use. By examining these misconceptions, we build an outlook for future research, highlighting the need to optimize materials and process conditions for the stepwise approach and to further explore catalytic processes that explicitly employ strategies for the preservation of methanol. While converting methane to methanol is an attractive process, making a catalytic—and commercially viable—route has presented severe difficulties. Here van Bokhoven and co-workers discuss the successes, problems and misconceptions in the field, focusing on the reaction with molecular oxygen over zeolites.