Acid properties of mordenites modified by dealuminatation
Abstract
Mordenite is dealuminated by hidrotherrnal treatment. Dealuminatation produces nonframework aluminium NFAL. Different types of NFAL were detected, one is a cationic type that is located in ion-exchange positions, other is a neutral type, and another an amorphous phase not "visible" to the 27Al RMN technique. The Lewis acid sites are associated with the NFAL species located in the zeolite pares. lt is not possible to find a relationship between the acid-strength of Bronsted acid sites and the structural aluminium content. However, the number of pyridine titrated acid sites increases after dealumination process. Adsorption studies also indicate presence of a mesoporous network in the materials that could decrease diffusional restrictions.
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