Solvent-Free Synthesis and n-Hexadecane Hydroisomerization Performance of SAPO-11 Catalyst

SAPO-11 catalysts are prepared by both solvent-free and hydrothermal methods. SAPO-11 samples prepared by the solvent-free method have a higher density of acid sites compared with the samples obtained by the hydrothermal method. We performed Si-29 NMR spectroscopy to determine the acid properties of the samples, and most Si species exist in the SAPO region. The SAPO-11 materials were loaded with the noble metal Pt at a content of approximately 0.5 wt.-%, and the bifunctional catalysts were applied in the hydroisomerization of n-hexadecane. Remarkably, a higher catalytic activity and isomer yield were obtained for the catalyst synthesized by the solvent-free method. In particular, the higher yield of multibranched isomers, including dibranched and tribranched isomers, can be ascribed to the lower nPt/nA ratio (an expression of the balance between metal and acid sites) accompanied by the longer residence of carbenium ions at the acid sites. The solvent-free samples can produce isomer products with lower pour points and enhanced low-temperature mobility.