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

Abstract

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.