Quantum-chemical studies of alumina. Part 2.—Lewis acidity

Abstract

The Lewis acidity of alumina has been investigated by ab initio molecular-orbital calculations for several cluster models. Three factors that may affect the acidity are discussed: (1) the coordinative environment around the active site, i.e. what atoms and how many atoms surround the exposed Al atom, (2) the lattice oxygen defects or cooperative enhancement of the acidity by more than two Al atoms in the surface and (3) the atomic configuration of the site, i.e. Al—O distances and O—Al—O angles. From these results and those from Part 1, the structures of the active site of the alumina catalyst is discussed.