High-resolution NMR studies of methyl acrylate adsorbed on silica and TiCl4-modified silica

High-resolution 13 C and 1 H NMR measurements on methyl acrylate adsorbed on silica and TiCl 4 -modified silica are reported. In both cases, samples with methyl acrylate adsorbed at equilibrium pressures of 38 or 2 Torr, then desorbed under vacuum have been studied. NMR spectra of both nuclei show clearly the adsorption of the methyl acrylate on unmodified silica and on the TiCl 4 -modified silica. Our results indicate the existence of two adsorbed species which demonstrates the existence of two types of acid sites on the TiCl 4 -modified silica. We also characterized the effect of adsorption on the methyl acrylate molecules.This work was made possible by the generous financial support of the Comision Interministerial de Ciencia y Tecnologia (Project MAT93-0224) and of the European Union (contract CHRXCT93-0276). One of us (E.P.) thanks the Diputacion General de Aragon for a grant.Peer reviewe