CuO/γ-Al2O3單分散催化劑的XAFS研究

The local structures of monolayer dispersive CuO/γ-Al2O3 catalysts prepared by means of impregnation have been investigated by XAFS technique. For the CuO/γ-Al2O3 sample with CuO loading 0.4 mmol/100 m^2 lower than the monolayer dispersion threshold, the XAFS results indicate that only the first coordination shell appears in the radial distribution function of Cu atoms, and that the R(subscript (Cu-O)) and coordination number in the first shell are 0.195 nm and 4, respectively. Hence, we consider that the CuO active species on the surface of γ-A12O3 are in the form of isolated atomic cluster (CnO(superscript n+ subscript 4)) Small amount of CuO nano-grains is formed onto the surface of γ-Al2O3 while the CuO loading is just equal to the threshold 0.8 mmol/100 m^2. For sample with CuO loading of 1.2 mmol/100 m^2, the local structure of Cu atom in Cuo/γ-Al2O3 is similar to that of CuO powder. On the basis of the XAFS results, a monolayer dispersion model of CuO/γ-Al2O3 catalysts has been proposed.