Reinforcement and reconfiguration of framework Al in P@ZSM-5 zeolite via in-situ phosphating strategy for efficient methanol-to-propylene

Abstract

In this work, a "bottom-up" strategy was proposed to one-step, in-situ synthesize P@ZSM-5 zeolites in a sodium-free system by elaborately self-designed tetrapropylphosphonium hydroxide as a new member of MFI-type zeolite organic templates inventory, and the interaction of phosphorus species with framework aluminum was investigated in detail. Multiple advanced characterizations confirm that the tetrahedrally-coordinated bidentate PIV-O2-AlIV structures are precisely customized and uniformly scattered in the zeolite channels. After experiencing harsh hydrothermal treatment (100 %H2O, 800 °C, 17 h), this new structure endows excellent hydrothermal stability of zeolite (crystallinity retention beyond 95 %) and reinforces its Brønsted acidity. Furthermore, methanol-to-propylene tests show that directly synthetic P@ZSM-5 zeolite performs extraordinarily long lifetime (180 h, WHSV = 1 h−1), enviable propylene selectivity (60.4 %) and propylene/ethylene ratio (ca. 4.3) compared to the counterparts, which is benefited from encouragingly olefinic cycle pathway. These findings afford value-filled opportunities in novel catalyst production mode and understandings for phosphorus-zeolite chemistry. Synopsis-A "bottom-up" strategy was demonstrated to one-step, in-situ synthesize P@ZSM-5 zeolite in a sodium-free system by elaborately self-designed tetrapropylphosphonium hydroxide. The resultant P@ZSM-5 catalyst with hyperuniformly-stable bidentate PIV-O2-AlIV structures exhibited extraordinarily long lifetime (180 h) and enviable propylene selectivity (60.4 %).