Manganese-promoted Rh supported on a modified SBA-15 molecular sieve for ethanol synthesis from syngas. Effect of manganese loading

A modified mesoporous molecular sieve SBA-15 possessing larger pore diameter, pore volume, and high hydrothermal stability was developed. Loaded with RhCl3 and Mn(NO3)2, the as-prepared SBA-15 performed excellently in catalyzing direct conversion of syngas to ethanol. The highest perimeter of Rh-MnO interface and ethanol yield were reached at the Mn/Rh weight ratio of about 1. High CO conversion, more than 90% in the first three hours, was obtained over the catalyst 7 wt% Rh-7 wt% Mn/SBA-15. Improved catalytic performance is attributed to the increase in the amount of reducible oxide, which resulted in an enhancement of the perimeter of the Rh-MnO interface when the Mn/Rh weight ratio is about 1, and the enhanced ability of rhodium to dissociate and to hydrogenate the carbon monoxide molecule by the addition of manganese.