Synthesis and characterization of Zr incorporated small crystal size Y zeolite supported NiW catalysts for hydrocracking of vacuum gas oil

Abstract

A series of Zr incorporated small crystal size Y zeolites were successfully synthesized by a direct hydrothermal method, and the corresponding NiW catalysts were prepared for the hydrocracking of vacuum gas oil (VGO). The synthesized zeolites and prepared catalysts were characterized by XRD, SEM, FTIR, Pyridine FTIR, H2-TPR and TEM techniques. The results show that the synthesized zeolites have uniform morphology and small crystal size, while Zr4+ incorporated into the framework of Y zeolite has been confirmed by XRD and FTIR. The amount of acid sites of xZrY zeolite slightly increases compared with that of Y zeolite by Pyridine FTIR. Moreover, the Zr4+ incorporation into Y zeolite can increase the W species reducibility, modulate the length and stacking of WS2 phase, and enhance the W species dispersion on the catalyst surface by H2-TPR and TEM, which favor to improve the hydrogenation activity of the catalyst to tune the balance between cracking activity and hydrogenation/dehydrogenation activity. Hence, the catalyst containing xZrY zeolite exhibits not only higher yield and selectivity of middle distillate but also slightly higher conversion of VGO compared with the catalyst containing Y zeolite.