MnO and CeO2 powders were mechanically mixed by a spatula and by milling to obtain loose-contact and tight-contact mixed oxides,respectively.The monoxides and their physical mixtures were characterized by X-ray diffraction(XRD),Brunauer-Emmett-Teller(BET),X-ray photoelectron spectroscopy(XPS),Raman,O2temperature-programmed desorption(O2-TPD),H2temperature-programmed reduction(H2-TPR)and NO temperature-programmed oxidation(NO-TPO).The MnOx-CeO2solid solutions did not form without any calcination process.The oxidation state of manganese tended to increase while the ionic valence of cerium decreased in the mixed oxides,accompanied with the formation of oxygen vacancies.This long-ranged electronic interaction occured more significantly in the tight-contact mixture of MnO and CeO2.The formation of more Mn4+ and oxygen vacancies promoted the catalytic oxidation of NO in an oxygen-rich atmosphere.
CeO2 and CuOx-CeO2 supported potassium catalysts were synthesized by wetness impregnation method. The catalysts were characterized by BET, NO-TPO, NOx-TPD and soot-TPO measurements. By the decoration of potassium and copper, the maximum soot combustion temperature of the ceria-based catalyst decreased to 338 and 379 °C in the presence and absence of NO under a loose contact mode, re- spectively. The pronouncedly enhanced NO oxidation ability by copper introduction and NOx storage capacity by potassium modification were especially important in the NOx-assisted soot oxidation reaction with the K/CuCe catalyst.
CuO-CeO2 catalysts were prepared by a urea precipitation method for the oxidative steam reforming of ethanol at low-temperature.The catalytic performance was evaluated and the catalysts were characterized by inductively coupled plasma atomic emission spectroscopy,X-ray diffraction,temperature-programmed reduction,field emission scanning electron microscopy and thermo-gravimetric analysis.Over CuOCeO2 catalysts,H2 with low CO content was produced in the whole tested temperature range of 250–450 C.The non-noble metal catalyst 20CuCe showed higher H2production rate than 1%Rh/CeO2 catalyst at 300–400 C and the advantage was more obvious after 20 h testing at400 C.These results further confirmed that CuO-CeO2 catalysts may be suitable candidates for low temperature hydrogen production from ethanol.
