MEASUREMENT OF SURFACE-ACIDITY BY P-31 NMR OF ADSORBED TRIMETHYLPHOSPHINE - APPLICATION TO VAPOR-DEPOSITED SIO2 ON AL2O(3) MONOLAYER CATALYSTS

Experimental procedures for quantitative estimation of surface acid by 31P NMR of adsorbed phosphines are discussed. These procedures are illustrated by application to a commercial silica-alumina cracking catalyst, and are applied to a series of silica on alumina monolayer catalysts prepared by chemical vapor deposition. The monolayer catalysts show a maximum in Brønsted acidity for a deposition of 8 SiO2 groups per nm2 of A12O3 surface. The evolution of Brønsted acid concentration as a function of amount of deposited silica can be accounted for by a simple kinetic model. © 1994 Academic Press, Inc.