Hydroisomerization of n-decane over Pt/SAPO-41 catalyst

A series of SAPO-41A zeolites with different silicon contents was hydrothermally synthesized from a new route by using phosphorous acid (H3PO3) as a phosphorus source. They were characterized by XRD, SEM, ICP, IR and NH3-TPD. The silicon content which was incorporated into the framework affected not only the acid sites but also the acid strength of SAPO-41A. The excellent performance of the hydroisomerization of n-decane can be obtained over SAPO-41A with proper silicon content in the framework. Bifunctional catalysts consisting of platinum supported on different types of zeolite (SAPO-41A, SAPO-41B, SAPO-11, MCM-22, Hβ) were investigated for the hydroisomerization of n-decane. Pt/Hβ and Pt/MCM-22 catalysts exhibited a higher hydrocracking activity due to their strong acid sites. The SAPO-based catalysts showed better catalytic performance for the hydroisomerization of n-decane, which can be primarily ascribed to their weaker and more suitable acid strength. Especially the SAPO-41A catalysts showed the highest hydroisomerization activity and selectivity among the SAPO-based catalysts. This is because their pore dimensions are larger than those of SAPO-11 and their grain sizes are smaller than those of SAPO-41B. Furthermore, some important variables affecting the activity and selectivity of a Pt/SAPO-41A catalyst, such as reaction parameters and metal content, were investigated. The conversion of n-decane was 84.04–92.29%, and the selectivity to isomers reached 90.50–85.30% over a 0.5 wt.% Pt/SAPO-41A3 catalyst when the reaction was performed at 310–330 °C. This can be attributed to the catalyst's suitable acid strength, distinct channel dimension, small crystal size and the proper ratio of the acid sites to the metallic sites.