Comparative study on stability and coke deposition over supported Rh and FePO4 catalysts for oxy-bromination of methane

Rhodium- and iron phosphate-based catalysts are by far the most promising catalysts for oxy-bromination of methane (OBM) reaction. However, most literature reported either Rh- or FePO₄-based catalysts, and the results were rarely studied in a uniform environmental condition. In this report, comparative study was conducted on silica- and silicon carbide-supported rhodium and iron phosphate catalysts with the main focuses on stability performance and coke deposition. The catalytic results demonstrated that the stability of both Rh- and FePO₄-based catalysts was greatly influenced by the supports used, and silicon carbide-supported catalysts showed much better anti-coking ability as compared with silica-supported ones. Temperature-programmed oxidation over the used catalysts further indicated that the coke formation mechanisms were completely different between silica-supported rhodium and iron phosphate catalysts. While cokes might be caused by condensation of CH₂Br₂ over supported iron phosphate, methane decomposition might be the reason for coke formation over silica-supported rhodium catalyst. These findings might pave the way for designing highly efficient and stable catalysts of the OBM reaction.