A comparative study of catalysts for the preferential CO oxidation in excess hydrogen

Selective CO oxidation in the presence of excess hydrogen was studied over metal oxides (CoO and CuO–CeO2), supported gold catalysts (Au/γ-Al2O3, Au/CuO, Au/CeO2/γ-Al2O3, Au/CuO–CeO2 and Au/CeO2), and supported Pt catalysts (Pt/γ-Al2O3, Pt–Ni/γ-Al2O3, and Pt–Co/γ-Al2O3). The methanation was dominant over CoO in the presence of excess H2. CuO–CeO2 was quite selective for CO oxidation at low temperatures. However, the presence of CO2 and H2O retarded its catalytic activity. No beneficial effect to CO2 selectivity was observed when Pt, Ru, Ni, and Co was added to CuO–CeO2 as a modifier. Supported gold catalysts showed the high CO conversion at low temperatures. However, the CO2 selectivity decreased noticeably with increasing H2 concentration in a reactant. Pt–Ni/γ-Al2O3 showed the highest CO conversion with a high CO2 selectivity over a wide reaction temperature among above catalysts examined at the same reaction condition. This catalyst also showed the best performance in the presence of 2 vol.% H2O and 20 vol.% CO2.