A new method called ultrasonic-assisted membrane reaction(UAMR)was reported for the fabrication of ceria-zirconia solid solution.A series of ceria-zirconia solid solutions with different Ce/Zr molar ratios were prepared by the UAMR method and characterized by Xray diffraction(XRD),N2 adsorption,hydrogen temperature-programmed reduction(H2-TPR),scanning electron microscope(SEM),and transmission electron microscopy(TEM)techniques.The UAMR method proved to be superior,especially when the Ce/Zr molar ratio was lower than 1,in fabricating ceria-zirconia solid solutions with large BET surface area,high oxygen storage capacity(OSC),and low reduction temperature.
Lijing MENGLicheng LIUXuehong ZIHongxing DAIZhen ZHAOXinping WANGHong HE
Ce-A12O3 catalysts prepared by co-precipitation are investigated both in NO oxidation by 02 and in selective catalytic reduction of NO by C2H2 （C2H2-SCR）. It is found that C2H2-SCR is initiated and controlled by NO oxidation to NO2 over A12O3. Ce loading on A12O3 is almost inactive for NO oxidation below 350℃, since NO2 strongly adsorbs on cerium oxide, leading to the active sites being blocked, which was characterized by temperature-programmed desorption of NO and NO2 and Fourier transform infrared spectroscopy after NO＋O2 coadsorption over the samples. However, in the case of C2H2-SCR, Ce loading on A1203 significantly improves the reaction by accelerating the NO oxidation step in the temperature range of 250-450℃, since the nitrate species produced by NO2 adsorption is an active intermediate required by C2H2-SCR.
The nanometer CeO2 powder was prepared by the method of microwave-assisted heating hydrolysis,and the nanometer CeO2-supported or ordinary CeO2-supported vanadia catalysts with different vanadium loadings(atomic ratios:100V/Ce=0.1,1,4,10,and 20) were prepared by an incipient-wetness impregnation method.Spectroscopic techniques(XRD,FT-IR,Raman and UV-Vis DRS) were utilized to characterize the structures of VOx/CeO2 catalysts.The results showed that the structures of CeO2-supported vanadium oxide catalysts de...
