CuOx/CeO2 catalysts were prepared by adsorption-impregnation method. CO conversion was tested over the catalysts pretreated under different conditions for preferential CO oxidation in H2, and the catalysts were characterized with X-ray photoelectron spectroscopy and temperature programmed reduction. Experimental results show that there are two kinds of copper, which are Cu+ and Cu 2+ in calcined CuOx/CeO2. Among them, the Cu+ is the key active component for CO oxidation. The main reason is as follows: CO is activated by copper for CO oxidation over CuOx/CeO2, while CO can not be activated by Cu 2+ . Only when Cu 2+ is reduced to Cu+ or Cu0, the copper may be active for CO oxidation, moreover, the experimental results show that the reduction of Cu 2+ does not lead to an increase of catalytic activity. So the active species is Cu+ in CuOx/CeO2 catalysts.
La modified Ni/γ-Al2O3 catalysts prepared by co-precipitation method using NaOH-Na2CO3 as a precipitator show high activity and selectivity for the partial oxidation of methane （POM）. Meanwhile, the addition of La is beneficial for the formation of an active component and stability of support. We investigated some factors including calcining temperature, nickel content, and space velocity, which turned out to have a strong influence on catalytic activity and selectivity. By XRD and TPR, it is concluded that Ni0 reduced from amorphous NiAl2O4 is the major active component for POM.
The Ni-CeO2 catalysts with different Ni contents were prepared by a co-precipitation method and used for Reverse Water Gas Shift (RWGS) reaction. 2wt.%Ni-CeO2 showed excellent catalytic performance in terms of activity, selectivity, and stability for RWGS reac- tion. Characterizations of the catalyst samples were conducted by XRD and TPR. The results indicated that, in Ni-CeO2 catalysts, there were three kinds of nickel, nickel ions in ceria lattice, highly dispersed NiO and bulk NiO. Oxygen vacancies were formed in CeO2 lattice due to the incorporation of Ni2+ ions into ceria lattice. Oxygen vacancies formed in ceria lattice and highly dispersed Ni were key active components for RWGS, and bulk Ni was key active component for methanation of CO2.
A very active catalyst of CuO/CeO2 was made by adsorption-impregnation method for preferential oxidation of CO in H2. The CO conversion is close to 100% and selectivity to CO oxidation is 96% over this catalyst at a low reaction temperature of 95 ℃ and a space velocity of 40000 cm3·g-1·h-1 in the reaction mixture of 1%CO, 1%O2, and 50%H2 balanced with N2. The effect of preparation conditions on catalytic performances was investigated. The catalytic performance of the CuO/CeO2 catalysts was compared with that of other CO preferential oxidation catalysts reported in literature.
