Catalytic partial oxidation of ethanol over noble metal catalysts

The catalytic partial oxidation of ethanol and ethanol-water was investigated over noble metal and metal plus ceria-coated alumina foams at catalyst contact times <10 ms. The effects of catalyst, flow rate, and water addition on selectivity and conversion were examined. Rh-Ce catalysts were the most active and stable. Without water addition, ethanol was converted directly to H2 with >80% selectivity and >95% conversion with Rh-Ce catalysts. Rh, Pt, Pd, and Rh-Ru produced less H2, with Pt and Pd producing <50% H2. Pt, Pd, and Rh also produced more CH4 and C2H4 than Rh-Ce. There was a smaller dependence on flow rate for Rh-Ce catalysts than other catalysts. Variation of a factor of 2 produced small changes in H2, and lower flow rates produced less CH4 and C2H4. Autothermal operation was achieved at as low as 10 mol% ethanol in water. Adding water to the Rh-Ce catalyzed reactor increased H2 selectivity and reduced selectivity to CO to <50% due to increased water-gas shift and steam reforming activity. With added water, the selectivity to H2 exceeds 100%, because both ethanol and water contribute H2. Also, the total selectivity of all unwanted products, mostly CH4, is <3% at the H2 production maximum with water addition.