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 tec hniques. The textural properties of the calcined samples were determined by low temperature nitrogen adsorption. Surface acidities were determined fro m the adsorption of n-butylamine. The crystal structure, surface area, pore volume and surface acid character were found to be dependent on the chemic al composition and calcination temperature. The heating of the samples at d ifferent temperatures led to the formation of ZnO, gamma-Al2O3 and ZnAl2O4 with various degree of crystallinity. The results of nitrogen adsorption re vealed 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 isopropan ol over the investigated catalysts was determined using a pulse microcataly tic 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 Else vier Science B.V. All rights reserved.