Optimized acidic fluoride medium ZSM-5 synthesis by using SAPO-34 as an alternative Al source

Incorporating aluminum into the zeolite framework is highly desirable because it generates acid sites, thereby enhancing catalytic performance. However, the introduction of aluminum into a zeolite in a fluoride medium, especially in the strongly acidic regions, is challenging. To address this issue in the synthesis of ZSM-5, SAPO-34, a silicoaluminophosphate zeolite material with strict alternation of -Al-O-P(Si)-O-Al-O- tetrahedra was employed as an alternative aluminum source. Thus, controllable adjustment of the Si/Al ratio of ZSM-5 was achieved by simple variation of the SAPO-34 amount in the synthesis mixture. Solid-state 27 Al and 29 Si NMR spectroscopy combined with chemical analyses proves that the resulting MFI-type zeolites contain considerable amounts of framework aluminum. And the Si/Al ratios could be adjusted below 30. Thus, this study provides a simple strategy for one-pot synthesis of heteroatom-containing zeolitic materials for various catalytic and separation applications.