Carbon dioxide reforming of methane with supported rhodium

Rhodium supported on γ-Al2O3 was an effective catalyst for reforming methane with carbon dioxide at low ratios of CO2/CH4. Unlike other metals tested, no carbon deposited on the catalyst in the temperature range 600–800°C. Kinetic experiments on a 0.5 wt.-% Rh/Al2O3 catalyst gave rate equations for the reforming and shift reactions. A model was constructed for conversion in a pellet by incorporating both the reverse reaction and the effect of external and internal diffusion. This model, when tested with the data from a pellet string reactor, gave very good agreement with conversions and product distributions. External diffusion was negligible but internal effectiveness factors were about 0.3 or more. The model was expanded to a large-scale packed bed with appropriate heat transfer parameters. Adjustable factors were determined by matching measured temperature profiles from pilot unit experiments. The catalyst later performed successfully in a solar receiver/reactor and shows potential for conventional processing.