Synthesis of Small Crystal Size Y Zeolite Catalysts with High Hydrocracking Performance on <i>n</i>-Hexadecane
Xiaohan Wang, Zhiqing Yu, Jinxiao Sun, Qiang Wei, Haoran Liu, Wenbin Huang, Luyuan Zhao, Si Meng, Yasong Zhou
Abstract
A series of in situ dodecyl trimethyl ammonium bromide (DTAB)-modified small-crystal Y zeolites have been successfully synthesized by DTAB addition to the seed synthesis procedure, which was used to create the small crystal size Y zeolites. Compared to the Y zeolites prepared without DTAB, the Y zeolites prepared with DTAB have a uniform morphology and mesoporous structure, a larger specific surface area (up to 32.3 m2 g–1 increase), a smaller crystal size (up to 66 nm reduction), and more Brönsted acid sites (up to 55 μmol/g increase). After loading with NiW, the corresponding NiW catalysts were utilized in the hydrocracking of n-hexadecane. It is evident from the catalytic performance that the catalysts containing DTAB-modified small-crystal zeolites have a higher yield and selectivity of primary cracking products compared with the Y zeolites without DTAB modification. Moreover, the conversion of n-hexadecane is also higher due to its low mass-transfer resistance, high dispersion, and sulfation of W species. When the molar ratio of DTAB/Al2O3 is 0.15, the corresponding catalyst has the optimum balance between cracking and hydro–dehydrogenation activity. Therefore, it has the most excellent catalytic performance and a 7.3% increase in C8–C12 yield.