Adsorption of water and methanol on zeolite Bro/nsted acid sites: An ab initio, embedded cluster study including electron correlation

Abstract

An embedded cluster model, employing a point charge field to correctly account for the electrostatic effect of the surrounding lattice, is used to study the adsorption of water and methanol at zeolite Bro/nsted acid sites. The effects of both the point charge field and electron correlation (studied at the second order Mo/ller–Plesset (MP2) and density functional theory (DFT) levels) are reflected in the predicted substrate structures, binding energies and ¹H NMR shifts. Both result in enhanced substrate binding to yield good agreement with experiment, and an increased degree of proton transfer to the substrate, an effect particularly evident in the case of methanol. There is a suggestion from a comparison with measured ¹H NMR shifts that this effect is somewhat overestimated by the model used here.