Acidity and Isomerization Activity of SAPO-11 Synthesized by an Improved Hydrothermal Method

Medium-pore molecular sieve SAPO-11 was synthesized using an improved hydrothermal method, which involved programmed heating of the synthesis gel in the presence of isopropanol. Products were characterized by X-ray diffraction, scanning electron microscopy, N2 adsorption, ammonia temperature-programmed desorption, infrared spectroscopy of adsorbed pyridine, and 29Si solid-state MAS NMR. The results indicated that the SAPO-11 sample synthesized by this method showed higher crystallinity, smaller particle size, and larger micropore volume than that prepared by the conventional hydrothermal method. Furthermore, the numbers of total acid sites and medium acid sites were enhanced. Thus, in the hydroisomerization of n-tetradecane, the Pt/SAPO-11 catalyst exhibited high activity and selectivity for isomers.