The hydroisomerization of n-decane over Pd/SAPO-11 bifunctional catalysts: The effects of templates on characteristics and catalytic performances

Two series of pure SAPO-11 silicoaluminophosphates (S11-B(x) and S11-P(x)) with different SiO2/Al2O3 molar ratios are synthesized by employing Di-n-butylamine (DBA) and Di-n-propylamine (DPA) templates, respectively. The effects of templates on the physicochemical properties of SAPO-11 samples are investigated by XRD, N2-adsorption, SEM, XRF, 29Si MAS NMR and Py-IR measurements. The results demonstrate that S11-B(x) samples reveal different morphology and lower strong Brønsted acid density compared with S11-P(x) samples. In addition, the linear correlation between detected and calculated total Brønsted acid densities of all samples is established. The Pd/S11-B(x) and Pd/S11-P(x) bifunctional catalysts are prepared by depositing 0.5 wt% Pd on SAPO-11 samples via the incipient wetness impregnation and hydrogen reduction methods and the n-decane hydroisomerization over all catalysts are tested. The catalytic results suggest that, due to the larger CPd/CH+ ratios and fewer strong Brønsted acid sites, Pd/S11-B(x) catalysts show higher yield of i-decanes compared with Pd/S11-P(x) catalysts, while the Pd/S11-B(0.4) shows the highest i-decanes yield of 76.75% among all catalysts. The results of long-term tests of 120 h suggest that Pd/S11-B(0.4) catalyst also has better stability because of slighter aggregation of Pd metal particles and fewer blockages of micropore openings.