Alkali-treatment technique - New method for modification of structural andacid-catalytic properties of ZSM-5 zeolites

ZSM-5 zeolite having a SiO2/Al2O3 molar ratio of 39.4 was treated in a NaOH alkali solution and the changes in structural and acidic properties were i nvestigated. A siliceous species was selectively dissolved from the framewo rk of zeolite, although a lower amount of Al was also eluted. In this proce dure, mesopores with a uniform size were formed on the zeolite, while the m icroporous structure remained. The acidic property was changed very little quantitatively or qualitatively, even though the catalytic activity for cra cking of cumene was enhanced by the alkali-treatment. This can be explained by the facts that adsorptive and diffusive properties of cumene through mi cropores of the ZSM-5 are increased by the creation of mesopores. (C) 2001 Elsevier Science B.V. All rights reserved.