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.