A study of the exchange sites per unit area of external surface of zeolite Al-ZSM-5

Abstract

The adsorption of the cationic dye methylene blue by the sodium-exchanged form of zeolite Al-ZSM-5 results in the release of a sodium ion from the external surface of the zeolite. The measurement of such sodium replacement, together with determinations of external surface area, has been used to assess the occurrence of sodium exchange sites per unit area of external surface of the zeolite. The external surface areas of the zeolite samples have a mean value of 106 m² g^–1 and the surface accommodates six molecules of dinitrogen per channel intersection. The sodium form of the Al-ZSM-5 zeolite has 15–25% of the total number of exchange sites on the external surface.