A STUDY ON THE CHEMICAL HETEROGENEITY OF ACTIVE SURFACE OF SOLID CATALYSTS

A method that can be used to characterize the chemical heterogeneity o f active surface of solid catalyst is given, The chemical adsorption b ehavior of three adsorbates on Ni-W/F-Al2O3-SiO2 catalyst and supporte d Ni catalyst has been investigated. On the basis of fractal geometry, the roughness fractal dimension (D-r,) and the chemisorption fractal dimension (D-c,) of two kinds of catalyst are estimated. We use the di fference between D-c,and D-r, to characterize the chemical heterogenei ty of active sites on the catalytic surface. As a result, the chemical heterogeneity of the acid sites of Ni-W/F-Al2O3-SiO2 catalyst is very great. As for supported Ni catalyst, the chemical heterogeneity of ac tive sites decreased when impregnating operation times in preparation of the catalyst increased. After impregnated four times, the chemical heterogeneity of its active surface of supported Ni catalyst is elimin ated. (C) 1997 Academic Press.