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A series of CuO/CeO2 catalysts were prepared through a two-step process: (1) CeO2 supports were firstly prepared by precipitation (P), hydrothermal (HT) and sol-gel (SG) methods, respectively; and (2) CuO was deposited on the above CeO2 supports by deposition-precipitation method. The as-synthesized CeO2 supports and CuO/CeO2 catalysts were characterized by N2-physisorption, XRD, XPS, Raman, and H2-TPR. The CuO/CeO2 catalysts were examined with respect to their catalytic activity for the water–gas shift reaction, and their catalytic activities are ranked as: CuO/CeO2-P > CuO/CeO2-HT > CuO/CeO2-SG. The results suggest that the CeO2 prepared by precipitation (i.e., CeO2-P-300) has the best thermal stability and the most amounts of surface oxygen vacancies, which make the corresponding CuO/CeO2-P catalyst present the largest pore volume, the smallest crystal size of CuO, the highest microstrain (i.e., the highest surface energy) and the most amounts of active sites (i.e., the moderate copper oxide (crystalline) interacted with surface oxygen vacancies of ceria). Therefore, the catalytic activity of CuO/CeO2 catalysts, in nature, depends on the thermal stability and the number of surface oxygen vacancies of the CeO2 supports previously prepared by different methods. [ABSTRACT FROM AUTHOR]

A series of aluminum promoted Cu/CeO2 nanocatalysts with aluminum content in the range of 0–5wt.% were prepared by co-precipitation method and examined with respect to their catalytic performance for the water–gas shift (WGS) reaction. The catalysts were characterized by XRD, BET, H2-TPR and cyclic voltammetry (CV) techniques. The results indicate that catalytic activity increases with the aluminum content at first, but then decreases with the further increase of aluminum content. Hereinto, Cu/CeO2 catalyst doped with 1 wt.% of aluminum shows the highest catalytic activity (CO conversion reaches 84.4% at 200 °C) and thermal stability for WGS reaction. Correlation to the results from above characterization, it is found that the variation of catalytic activity is in very agreement with that of the surface area, the area of peak γ (i.e., the reduction of surface copper oxide (crystalline forms) interacted with surface oxygen vacancies on ceria), and the area of peak C2 and $$\hbox{A}_{1} (\hbox{Cu}^{0}\,\leftrightarrow\,\hbox{Cu}^{2+}$$ in cyclic voltammetry process), respectively. Enough evidence was found for the fact that the metallic copper (Cu0) interacted with surface oxygen vacancies on ceria is the active site for WGS reaction over Cu/CeO2 catalysts. [ABSTRACT FROM AUTHOR]

For Au-ceria catalysts prepared by deposition-precipitation method, catalytic performance of water gas shift reaction was studied in different La loadings. In the complete doping range, ceria retains with its cubic fluorite structures. BET, XRD, H2-TPR, HRTEM studies showed that La doping can improve the activity of Au-ceria catalyst by stabilizing ceria and modifying its morphology. In addition, the test of catalyst stability evaluation also proved a better stability performance of Au-ceria catalyst can be realized by appropriate La doping. [ABSTRACT FROM AUTHOR]

The activity and stability of Au/Fe2O3–MO x catalysts (M = Zr, Mg, Ca, Ni, La, Cu, Zn, Al, Ba, Cr, Co, Ce, Mo, Bi, Ti, Mn) in water-gas shift reaction were investigated extensively. The WGS activity and stability of Au/Fe2O3 is improved significantly upon addition of ZrO2 and to a lesser extend MgO, CaO, NiO, La2O3, Cr2O3, CuO. In contrast, Bi, Ti and Mn oxides seriously decrease the catalytic activity while additions of Zn, Al, Ba, Co, Ce and Mo oxides do not influence evidently the catalytic activity and its stability. Based on the characterization using the methods of BET-surface area and pore structure XRF, XRD, and H2–TPR for some of as-prepared and spent samples, it could be concluded that the catalytic activity of gold catalysts supported on composite oxide of Fe2O3–MO x depends not only on the dispersion of the gold particles but also on the reduction property of composite oxide supports, regardless of the fluctuation of gold loading and some change of specific surface area and pore structure due to introduction of the modifying metal oxides. The improvement of catalytic stability may be attributed to the comparative stabilization of high dispersion of gold particles and uneasily sintering of Fe3O4 crystallites during the catalytic operation. However, the chemical (electronic) effects exerted by the modifying addition of metal oxides on the catalytic performance of gold catalyst may not be ruled out. [ABSTRACT FROM AUTHOR]