Sorption of hydrocarbons and water in silanated and unsilanated partial H-forms of zeolite Y

Abstract

A study has been made of sorption at 30°C of n-hexane, 2-methylpentane, 2,2-dimethylbutane, cyclohexane, benzene and water in zeolite Y with 0, 31, 54 and 73% of the Na replaced by H, both before and after silanating these sorbents to different extents. Hydrocarbons were sorbed at 63 ± 2 Torr and water at 10 Torr. The three unsilanated partially H-exchanged forms of Y, in formation from Na–Y, each lost nearly the same fraction of sorption capacity for hydrocarbons and water as compared with Na–Y. It is suggested that regions of impermeable amorphous material had formed in similar amounts in each partial H-form, nucleated and developed on or in a matrix of parent crystal, as a result of bond breaking and re-making with different partners, associated with proton migration. Compared with the corresponding unsilanated form the silanated 31 and 54% H-exchanged Y gave enhanced uptakes. This was attributed in part to increased sorption energy because of interaction of sorbate not only with lattice atoms but also with the extra atoms introduced by silanation and subsequent reactions. While the silanated 31 and 54% H-exchanged Y freely sorbed all the hydrocarbons and water the silanated 73% H-forms were heavily blocked. Possible causes of this strong difference were discussed.