Differential utilization of the surface of aluminum oxide in the production of complex and mixed catalysts

1. The catalytic activity of a series of ZnO-Al2O3 catalysts, produced by the adsorption of diethyl-zinc in amounts from 0 to 100% of monolayer coverage on two samples of Al2O3 of different genesis, was investigated in the decomposition of isopropanol in an adsorbed layer and in a pulsed chromatographic system. The catalytic activity is not a linear function of the composition of the catalyst; moreover, the portions possessing the greatest adsorption capacity with respect to diethylzinc proved to be the most favorable for the formation of active centers in the dehydrogenation reaction. 2. The method of preliminary blockage of part of the surface with pyridine, which made it possible to change the nature of the group of portions of the surface covered by zinc oxide, permits the production of ZnO-Al2O3 catalysts which, with the same ZnO content, differ substantially in catalytic activity. The positions of the portions most favorable for the formation of ZnO-Al2O3 dehydrogenating centers, on the curve of the distribution of parts of the surface of the initial aluminum oxide, depend upon the genesis of the aluminum oxide sample. 3. At the same zinc oxide content, catalysts produced by the method of adsorption from the gas phase substantially exceed samples prepared by the usual method of impregnation in activity.