Controllable synthesis of SAPO-11/5 intergrowth zeolite for hydroisomerization of n-hexane

Intergrowth zeolites are always synthesized to combine advantages of each single phase. Herein, the SAPO-11/5 intergrowth zeolite with controlled AFI/AEL phase ratios was synthesized and used for the n-hexane hydroisomerization. The obtained samples were characterized by XRD, TEM, SEM, N-2 adsorption-desorption, NH3-TPD and Si-29 MAS NMR. The new morphology different from each single phase is obtained over the SAPO-11/5 intergrowth zeolite. It also exhibits intermediate surface acid density and pore volume between the SAPO-11 and SAPO-5. With the increased AFI/AEL ratio, more surface acid sites and larger pore volume are obtained. The SAPO-11/5 intergrowth zeolite was transformed into bifunctional catalysts (Ni/SAPO-11/5-2) by loading with 4.0 wt% Ni via the impregnation method. This novel catalyst shows improved isomers selectivity and yield than each single phase catalyst in the n-hexane hydroisomerization, which is mainly attributed to the intermediate pore structure and surface acidity. Furthermore, the Ni/SAPO-11/5-2 also illustrates higher di-branched isomers selectivity (7.7%) than the Ni/SAPO-11 (2.4%) catalyst, favoring increasing the octane number of gasoline. This work provides an alternative approach to simultaneously regulate surface acidity and pore structure for the hydroisomerization catalyst.

Automated summary

Intergrowth zeolites combine advantages of single phases, with the SAPO-11/5 intergrowth zeolite showing intermediate surface acidity and pore volume by controlling the AFI/AEL ratio. The Ni/SAPO-11/5-2 bifunctional catalyst exhibits improved isomers selectivity and yield in n-hexane hydroisomerization, attributed to its unique pore structure and surface acidity.