Effect of syngas conversion and catalyst reduction temperature in the synthesis of ethanol: concentration of water vapor in mesoporous Rh/MCM-41 catalyst

• We evaluate the performance of a Rh/MCM-41 catalyst at different reaction conditions.
• High selectivity to CO2 is observed at a large syngas conversion level.
• High selectivity to CO2 is observed at different catalyst reduction temperatures.
• High selectivity to CO2 is observed over the non-reduced catalyst.
• Water vapor may be concentrated in the pores of Rh/MCM-41 which may promote the WGSR.

Rh-based catalysts typically show low selectivity to CO2 in the synthesis of ethanol from syngas. However, a novel mesoporous Rh/MCM-41 catalyst shows high selectivity to CO2 in a large range of syngas conversions; 1% to 68%, regulated by adjusting the operation conditions (270–430 °C, 30–90 bar and 6000–40,000 ml(syngas)/gcat h). The same effect is obtained at different catalyst reduction temperatures (200 °C and 500 °C) as well as on the non-reduced catalyst. A high concentration of water vapor seems to occur in the pores of Rh/MCM-41 which may promote the water-gas-shift-reaction, producing extra CO2 and H2.

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