Hierarchical Y zeolite with accessible intracrystalline mesopores and enhanced hydrocracking performances via sequential multi-carboxyl acid and fluoroborate post-treatments

Abstract

Hierarchical Y zeolite that combines the intrinsic microporosity with mesoporosity can alleviate diffusion limitation in hydrocracking catalyst. In this study, hierarchical Y zeolites with abundant mesopores that connect the interior of the zeolite crystals to the external surface were successfully synthesized by post-synthesis dealumination using citric acid (C6H8O7) and/or ammonium tetrafluoroborate (NH4BF4) as agents. The results show that C6H8O7 can effectively extraction framework aluminum species (FALs), while NH4BF4 mainly interacts with extra framework aluminum species (EFALs). Via sequentially adopting C6H8O7 and NH4BF4 (denoted as DAY-C-F), such interconnected mesopores can be effectively introduced without sacrificing the zeolite crystallinity. The results of the scaled-up hierarchical Y zeolite reveal that the above mentioned post-treatment strategy is feasible and reproducible for potential industrial manufacturing and applications. The hydrocracking test results reveal that the naphtha yield for the catalyst derived from the C6H8O7-NH4BF4 sequentially treated USY is higher than that of the counterpart made from commercial USY.