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, N2 adsorption-desorption, NH3-TPD and 29Si 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.