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 bulk liquid at 273 to 338K was measured volumetrically (tables 59 and 60). The diffusivity and activation energy for diffusion were found to be strongly affected by the side-groups attached to the benzene nucleus, polarity, critical molecular size and configuration of sorbate molecules. The influence of configuration and/or flexibility (compressibility to the zeolite channel diameter) played a vital role in governing penetration and configurational diffusion (following penetration) of sorbate molecules in the zeolite channels. The influence of critical size and configuration of sorbate molecules, on their entry into the zeolite channel and also their configurational diffusion after sorption, could be explained by the shuttlecock−shuttlebox model for sorption/diffusion of bulky molecules in medium-pore zeolites. The influence was explained by taking into consideration the orientations in different conformations and compressibility in the movement, in different directions, of the sorbate molecules.

Single-Component Sorption/Diffusion of Cyclic Compounds from their Bulk Liquid Phase in H-ZSM-5 Zeolite. V.R.Choudhary, V.S.Nayak, T.V.Choudhary: Industrial and Engineering Chemistry Research, 1997, 36[5], 1812–8

Table 59

Diffusivity in H-ZSM-5 at 308K