Light-driven flow synthesis of acetic acid from methane with chemical looping

A light-driven, chemical looping approach to CH3COOH synthesis from methane using a Pd/PdO-WO3 nanocomposite is reported. Methane is converted to methyl and carbonyl intermediates at the Pd and PdO sites, respectively, to produce CH3COOH. Oxidative carbonylation of methane is an appealing approach to the synthesis of acetic acid but is limited by the demand for additional reagents. Here, we report a direct synthesis of CH3COOH solely from CH4 via photochemical conversion without additional reagents. This is made possible through the construction of the PdO/Pd-WO3 heterointerface nanocomposite containing active sites for CH4 activation and C-C coupling. In situ characterizations reveal that CH4 is dissociated into methyl groups on Pd sites while oxygen from PdO is the responsible for carbonyl formation. The cascade reaction between the methyl and carbonyl groups generates an acetyl precursor which is subsequently converted to CH3COOH. Remarkably, a production rate of 1.5 mmol g(Pd)(-1) h(-1) and selectivity of 91.6% toward CH3COOH is achieved in a photochemical flow reactor. This work provides insights into intermediate control via material design, and opens an avenue to conversion of CH4 to oxygenates.

Automated summary

A light-driven, chemical looping approach using a Pd/PdO-WO3 nanocomposite has been developed for the synthesis of CH3COOH from methane. By utilizing the active sites on the PdO/Pd-WO3 heterointerface nanocomposite, methane is converted directly to acetic acid without the need for additional reagents. This work provides new insights into intermediate control and offers a promising route for the conversion of methane to oxygenates.