Adsorption and reaction in confined spaces

Abstract

Adsorption of molecules in ordered microporous solids involves specific energetic and entropic effects. The molecular stacking in such confined spaces leads to selectivities different from those observed on traditional mesoporous or amorphous materials. Examples of packing and entropic effects in hydrocarbon adsorption on zeolites are presented. Rotational entropy driven separation of n-liso-alkane mixtures in zeolite MCM-22, inverse shape selectivity in SAPO-5, chain length induced selectivity reversal in ZSM-5 and stacking effects in the liquid phase separation of alkanelalkene mixtures on Faujasites are discussed. It is shown that entropy induced selectivity effects in the adsorption of alkane mixtures affect selectivity and isomer yield in hydro-isomerisation processes. Copyright © 2006, Institut français du pétrole.