A Two-Patch Heterogeneous Model with Surface Phase Transition for Benzene Adsorption on Silicalite

Abstract

A solid is commonly called heterogeneous if the adsorption potential is not uniform throughout the surface. The nonuniformity can be caused by several factors such as existence of ions, pore size distribution, and chemisorbed contaminants. Heterogeneity is a system behavior, regardless of the cause of potential variation. A solid may induce heterogeneous surface phase behavior when a molecule is adsorbed while it may act homogeneous with another adsorbed molecule. Consider a flat surface where regularly space ions impose “potential islands” in the adsorption space. The adsorption potential experienced by a small molecule is different from point to point on the surface, the system is heterogeneous. The total potential experienced by another molecule will be uniform if it is large enough to be exposed to several potential islands simultaneously. Such a system behaves homogeneous although the solid is said to be heterogeneous due to the existence of ions.