A model cluster study of the acid-base properties of phosphate catalysts

Various model clusters have been chosen to simulate the surfaces of phosphate catalysts (phosphoric acid, boron phosphate, aluminum phosphate and silicon phosphate). Semi-empirical CNDO/2 calculations have been performed, and the calculated electronic parameters are utilized to predict the surface acid-base characteristics of these catalysts and the effect of water adsorption. The order of acidity and basicity of these catalysts as predicted from the calculated values of HOMO and LUMO energy levels is in semi-quantitative agreement with experimental observation. © 1985.