The role of sorbate in the determination of preferential adsorption sites in zeolite HY: A theoretical study

Zeolite HY is a crucial acid catalyst in petroleum refining. The effect of molecular properties of a sorbate on its preferential adsorption site in zeolite HY characterized by non-uniform zeolitic charge distribution was investigated using the recently developed and validated faujasite supercage-based docking method. In the adsorption of benzene, the charge distribution in the zeolite HY structure affects the sorption site. This resulted in either the proton H(1) site or the unprotonated 4-membered ring site as the most stable site. However, only the 12-membered ring window site having the sorption energy of 120.7 ± 2.5 kJ mol−1 was found to be the most stable site for the adsorption of hydrobenzoin, regardless of the charge distribution in the supercages examined. The molecular properties (e.g., size, shape, number of hydrogen bond donors) of hydrobenzoin are thus likely to be the dominating factor that determines the preferential sorbate location. Therefore, the preferred adsorption site of a sorbate in the faujasite supercage may depend either on the charge distribution in the zeolite HY structure or on the molecular properties of the adsorbate itself, depending upon the nature of the adsorbate.