Different Carriers-Supported Rh-Based Catalysts for Oxidative Bromination of Methane

Oxidative bromination of methane over Rh-based catalysts supported on different carriers was studied using a conventional fixed-bed reactor at atmosphere pressure. It was found that inert supports such as SiC and SiO(2) were in favor of the selectivity for bromomethanes, whereas deep oxidation occurred over ZrO(2) and TiO(2) oxides. H(2)-temperature-programmed reduction experiments confirmed that inert carrier-supported Rh catalysts were more difficult to be reduced than the metal oxide-supported Rh catalysts. Thermodynamic analysis revealed that the steam reforming of bromomethanes was promoted at higher reaction temperatures. It was concluded that the superior performance of the inert carrier-supported catalysts could be ascribed to the medium redox ability, which suppressed the steam reforming reaction. Among the catalysts studied, Rh/SiC showed the highest methane conversion and selectivity for bromomethanes, and therefore the key parameters of catalyst preparation and reaction conditions were optimized on this catalyst. About 20% methane conversion and 90% total selectivity for bromomethanes were achieved on a single pass at 620 degrees C with the gas hourly space velocity and liquid hourly space Velocity of 900 and 3.0 ml/(g.h), respectively. No deactivation happened during 100 h time-on-stream.