AN AB-INITIO STUDY OF THE CH2O ADSORPTION ON THE MGO(100) SURFACE - EFFECTS OF REPLACING THE ACTIVE MG2+ ION BY DIFFERENT METALLIC CATIONS

A theoretical analysis of the interaction between formaldehyde, CH2O, and the MgO (100) surface is reported. Ab initio Hartree-Fock calculat ions are carried out using an embedded cluster approach in which the e nvironment is described by both total ion potentials and point charges . The cluster selected to describe the CH2O-surface interaction is CH2 O[MgO5](8-), in which the formaldehyde oxygen is coordinated to the Mg 2+ ion. The effect of the addition of metallic cations to the catalyst is analysed by replacing the cluster Mg2+ ion by Na+, Al3+, Sc3+ and Ti4+ so as to modify the Lewis acid properties of the surface. The dif ferent contributions to the adsorbate-surface interaction are analysed , and the theoretical vibrational frequencies are discussed.