Single-component sorption/diffusion of cyclic compounds from their bulk liquid phase in H-ZSM-5 zeolite

Abstract

Single-component sorption/diffusion of cyclohexane, pyridine, benzene, toluene, aniline, ethylbenzene, xylene isomers, n-propyl- and isopropylbenzenes, and mesitylene in H-ZSM-5 (Si/Al = 39.7) zeolite from their bulk liquid phase at 273-338 K has been measured volumetrically. The diffusivity and activation energy for the diffusion are found to be strongly influenced by the side groups attached to the benzene nucleus, polarity, critical molecular size, and configuration of sorbate molecules. However, the influence of configuration and/or flexibility (i.e., compressibility to the zeolite channel diameter) plays a vital role in controlling/deciding the penetration (or entry) and configurational diffusion (after penetration) of sorbate molecules in the zeolite channels. The influence of critical size and configuration of sorbate molecules, on their entry in the zeolite channel and also their configurational diffusion after sorption, can be explained by the shuttlecock-shuttlebox model for sorption/diffusion of bulky molecules in medium-pore zeolites. The influence is explained by taking into consideration the orientations in different conformations and compressibility in the movement in different directions of the sorbate molecules.