Acid attack theory of dealumination in cation-exchanged faujasite

Abstract

The chemical extraction of Al atoms from X and Y zeolites during ion-exchange procedures using 1 N metal chloride solutions was experimentally and theoretically studied to reveal the effect of cation on the dealumination. The cation effect on the dealumination process was found to be related to the pH of the solution. Regardless of the cation, similar extents of dealumination were observed for the HCl solutions with the pH values equivalent to those of the metal chloride solutions. This suggests that the dealumination is initiated by an acid attack. CNDO2 calculations were made on a six-ring model for a representative faujasite cluster to obtain atomic charge densities, Wiberg bond orders, and total energies. Total energy changes along reaction steps indicate a high possibility of the acid attack reaction mechanism.