COMPARING HOMOGENEOUS AND HETEROGENEOUS ACID CATALYSTS BY A DENSITY-FUNCTIONAL BASED SENSITIVITY ANALYSIS OF THEIR INTERACTION WITH CARBENIUM IONS

An attempt has been made to develop a quantitative comparison of the properties of homogeneous and heterogeneous catalyst systems. The bond formation, and its projected covalent character, of a carbenium ion with the surface of zeolites and with water molecules in solution served as a basis to collect quantitative data. These data are the global electronegativity and hardness and the local softness (reactivity parameter of atoms-in-molecules) as these can be calculated for solids and molecules in the EEM formalism. A consistent model could be developed for a quantitative and qualitative comparison. It shows that generally, hydrated carbenium ions remain more ionic than those interacting with the surface of silicates or zeolites.