Direct Chemical Conversion of Methane into Acetic Acid

Methane, as an abundant and relatively clean resource, has primarily been converted into various chemical products via indirect conversion through synthesis gas, a mixture of CO and H2. Recently, interest in direct methane conversion technologies with lower energy consumption has increased. Compared to research on methanol production via selective oxidation of methane, studies on the direct conversion of methane to acetic acid have been relatively scarce, but significant research progress has been made recently. This review classifies reports on the direct conversion of methane into acetic acid according to catalyst type (homogeneous vs. heterogeneous catalysts) and reaction conditions, and discusses the advantages and disadvantages of each approach. A relatively high yield of acetic acid can be achieved using CO as a carbonylating agent. However, the direct conversion of methane and CO2 into acetic acid is more attractive from an environmental perspective. Recent advances in the field of electrocatalysis for this purpose are noteworthy. Other non-thermal catalytic methods, including photocatalysis, photoelectrocatalysis, and plasma processes, are also included. Based on the current state-of-the-art research trends in this field, future research directions are proposed.