Abstract: A novel active catalyst of Na-Rh/γ-Al2O3 was prepared by impregnation and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and N2 adsorption-desorption. The catalytic performance of Rh/γ-Al2O3 and Na-Rh/γ-Al2O3 catalysts for the selective oxidation of CO in the presence of excess hydrogen was compared, and the effect of pretreatment on the catalytic activity was investigated. The 5%Na-0~5%Rh/γ-Al2O3 catalyst maintains its activity for CO oxidation for more than 100 h in the presence of hydrogen and moisture. The conversion of CO and CO2 selectivity up to 100% and 70%, respectively, were obtained at 100 ℃, GHSV=2~25×104 h-1, 1~4%O2, 2%CO, and 70%H2. XPS results indicated that the electronic interaction between Na and Rh causes a transfer of electron density from Na to Rh, which increases the back-donation of electrons from the filled d orbitals of Rh to the CO 2π* antibonding molecular orbitals and results in a weakening of the C[KG-45x]=[KG-20x]O bond. Highly dispersed Rh was found on the surface of the promoted catalysts. N2 adsorption-desorption results revealed that the specific surface area decreases after the addition of Na, but the average pore size becomes larger, which provides more spaces for CO oxidation.

Key words: carbon monoxide, selective oxidation, promoter, sodium, rhodium catalyst, alumina, fuel cell