Acidity characterization of dealuminated H-ZSM-5 zeolites by isopropanol dehydration

摘要

A series of dealuminated ZSM-5 zeolites with various framework Si/Al ratios were prepared byrndifferent methods (HCl, ammonium hexafluorosilicate, steaming). The number of acid sites thatrncorrespond to the high-temperature desorption peak of the ammonia-TPD spectra of all therndealuminated samples is in 1:1 mole analogy to the framework Al (FAl), irrespective of the degreernand the type of dealumination method. The catalytic activity of the H-ZSM-5 zeolites for isopropanolrndehydration is linearly related to the number of acid sites that correspond to the FAl-contentrn(Br?nsted acidity). The Si-Al amorphous phase that is formed in the high-temperature steamedrnsamples affects activity and induces different product selectivity for propene and diisopropyl ether.