Theoretical study of catalytic decomposition of acetic acid on MgO nanosurface

Abstract

The adsorption and decomposition of acetic acid on the surface of MgO have been investigated using the representative cluster models and at the MP2/6-31G(d,p) level of theory. Adsorption of acetic acid on (MgO)n clusters for n=4, 6, 9, and 12 were carried out by fully optimizing the acetic acid while geometry of the MgO fragment was kept frozen at the same level of theory as used for acetic acid. It is revealed that the adsorption energy of acetic acid varies with the cluster size. Strong chemisorption with −197kJmol−1 has been observed for acetic acid adsorption on (MgO)4 surface. Decarboxylation path of acetic acid on (MgO)4 surface was investigated by locating the transition state and calculating the Intrinsic Reaction Coordinate. IRC calculation located a physisorbed structure with 325kJmol−1 of energy higher than the chemisorbed structure. Detail analysis of adsorbed acetic acid species on (MgO)4 surface and transition state by using Atoms in Molecules (AIM) method and ChelpG method for polarization of electron density in acetic acid upon adsorption revealed that the adsorption of acetic acid is a destructive adsorption preceded by a physisorption. Net energy required for the decarboxylation is found to be about 132 kJmol−1 on (MgO)4 surface.