MESOPORE FORMATION DURING STEAM DEALUMINATION OF ZEOLITES - INFLUENCEOF INITIAL ALUMINUM CONTENT AND CRYSTAL SIZE

The texture of a series of dealuminated mazzites, with different compo sitions and crystal sizes, prepared by combined steam and acid treatme nts has been investigated by N-2 and hydrocarbon sorption, TEM and Xe- 129 NMR spectroscopy. Crystal size is shown to affect the fraction of mesopores with ink-bottle openings leading to a steep nitrogen desorpt ion at a relative pressure p/p(0) of 0.42. The composition of the pare nt zeolite determines the volume and the size of the mesopores, both o f them decreasing with the aluminum content. Results are compared to t hose obtained on five additional zeolite structural types and lead to a unique relation between the mesopore volume generated by dealuminati on and the aluminum fraction in the starting solid.