Direct oxidative carbonylation of waste methane to acetic acid over Rh/zeolite catalysts

Document Type

Article

Publication Date

2-5-2026

Abstract

Direct oxidation of methane to oxygenates remains challenging in heterogeneous catalysis. In this work, direct oxidative carbonylation of low-concentration methane to acetic acid has been investigated over Rh/zeolite catalysts. Formation of acetic acid over Rh/ZSM-5 is shown to be far superior compared to a range of other Rh/zeolite catalysts, including Rh/Z-beta, Rh/Z-Y, Rh/Mor, Rh/Fer, and Rh/SSZ-13. The importance of the 3D channel structure of ZSM-5 is emphasised by a comparison with unidirectional Rh/ZSM-23 which showed much lower production of acetic acid. Acetic acid production is found to be maximum at a SiO2/Al2O3 ratio corresponding to ZSM5–50. Isolated Rh is identified as the active site for liquid oxygenate production with 0.09 wt% Rh/ZSM5 giving the highest acetic acid production. Higher Rh loading leads to a drop in production due to the gradual formation of Rh nanoparticles. Acetic acid production is shown to be strongly pressure dependent consistent with 2nd or higher order apparent kinetics compared to apparent 1st order for C1 products. Competing direct CO oxidation to CO2 was responsible for above 85 % of the total CO2 production. These findings highlight the critical role of zeolite topology in enhancing selective methane valorisation over Rh catalysts, and provide insights into developing practical catalytic processes for low-carbon chemical manufacturing.

Publication Source (Journal or Book title)

Applied Catalysis A General

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