Structure, texture and catalytic activity of ZnO/Al2O3 catalysts

The structural and phase changes occurring in coprecipitated zinc-aluminum hydroxide system were studied by thermoanalytical and X-ray diffraction techniques. The textural properties of the calcined samples were determined by low temperature nitrogen adsorption. Surface acidities were determined from the adsorption of n-butylamine. The crystal structure, surface area, pore volume and surface acid character were found to be dependent on the chemical composition and calcination temperature. The heating of the samples at different temperatures led to the formation of ZnO, gamma-Al2O3 and ZnAl2O4 with various degree of crystallinity. The results of nitrogen adsorption revealed that S-BET values of the different solids decrease progressively on increasing precalcination temperature and ZnO content due to sintering. The same was found true for the surface acidities. The conversion of isopropanol over the investigated catalysts was determined using a pulse microcatalytic technique. The dehydrogenation of isopropanol was found to be dependent on the chemical composition. The dehydration of isopropanol is independent of the surface area but related to the surface acid density. (C) 1999 Elsevier Science B.V. All rights reserved.