Abstract
Selective oxidation of CO in H-2-rich streams was carried out over a series of CuO-CeO2 catalysts doped by different transition metals (Mn, Fe, Ni,Ti, Co and Cr). The effect of the dopants on the structure and catalytic properties of CuO-CeO2 catalysts was investigated by N-2 adsorption/desorption, X-ray diffraction (XRD), H-2 temperature-programmed reduction (H-2-TPR), X-ray photoelectron spectroscopy (XPS), Raman spectra and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) techniques. The results show that the addition of Mn and Fe plays a beneficial role in extending the low-temperature catalytic activity of CuO-CeO2 catalysts, whereas the introduction of Cr and Co leads to a negative effect on the catalytic activity and resistance against CO2 and H2O. The superior catalytic performance of CuO-CeO2 catalysts with Mn and Fe doping originates from the enhanced interaction between copper and ceria, owing to the formation of more Cu+ and oxygen vacancies in the solid solution framework While the poor catalytic activity of the Co doped counterpart is mainly ascribed to the substitution of introduced cobalt ions for copper ions in ceria lattice, resulting in the segregation of copper ions from the ceria lattice and the consequent aggregation of copper species on the ceria surface. The doping of Cr into CuO-CeO2 structure remarkably weakens the interaction between copper and ceria, which decreases the reducibility of copper species and inhibits the formation of Cu+. It accounts for the lowest catalytic activity. (C) 2011 Elsevier B.V. All rights reserved.