Selective oxidation of CO in excess hydrogen over catalysts

Alumina was incorporated with the solid solutions of Ce x Zr 1 - x O 2 to form Ce x Zr 1 - x O 2 – Al 2 O 3 mixed oxides, by the suspension/co-precipitation method, to be used as supports of CuO / Ce x Zr 1 - x O 2 – Al 2 O 3 catalysts. They were characterized, and the effects of Al 2 O 3 on the selective oxidation of CO in excess hydrogen were examined. Incorporating Al 2 O 3 increased the dispersion of Ce x Zr 1 - x O 2 , but did not change their main structures and did not weaken their redox properties. Doping zirconium into CeO 2 increased the mobility of lattice oxygen and enhanced the activity of the 7 % CuO / Ce 0.9 Zr 0.1 O 2 – Al 2 O 3 catalyst in the selective oxidation of CO in the H 2 -rich feed. The promotion of CO oxidation became weaker as the fraction of Zr 4 + dopant increased above 0.1. A small amount of Zr 4 + dopant and an appropriate amount of incorporated Al 2 O 3 could obtain a good candidate such as 7 % CuO / Ce 0.9 Zr 0.1 O 2 – Al 2 O 3 ( 20 % ) for a preferential oxidation (PROX) unit in a polymer electrolyte membrane fuel cell system for removing CO. Its activity was comparable with, and its selectivity was much larger than, that of the noble catalyst 5 % Pt / Al 2 O 3 .