Insight into the adsorption mechanism of benzene in HY zeolites: the effect of loading

Abstract

An interesting two-stage adsorption mechanism was first proposed for the benzene/HY system by Metropolic Monte Carlo (MMC) simulations at loadings below and above an “inflection point”, and were composed of processes labeled “ideal adsorption” and “insertion adsorption”, respectively. Below the inflection point (from infinite dilution up to 32 molecule/UC for all Si : Al ratios), benzenes were located on the sorption sites inside the supercages with an ideal adsorption geometry configuration, which is in accordance with previous studies. Above the inflection point, the benzene molecule tended to insert into the space between existing adsorbed benzenes, and no obvious rearrangement was observed for previously adsorbed benzenes. It was found that the proposed adsorption mechanism existed independently of the Si : Al ratio, while the inflection point shifted to a higher loading for zeolite with a lower Si : Al ratio. This is due to increased utilization of the 12-T ring caused by the contribution of the H1 site in zeolite with a lower Si : Al ratio, which result in less crowed adsorption at loadings approaching saturation.