The Effect of Additional Zeolites in Amorphous Silica-Alumina Supports on Hydrocracking of Semirefined Paraffinic Wax

摘要

The amorphous SiO_2-Al_2O_3 supports (SA-x) with different SiO_2 weight ratios (x) were prepared by a sol-gel method. The NiW active components were loaded over the supports using an organic matrix combustion method. Semirefined 56# wax was used as the model feedstock of F-T synthetic wax for hydrocracking in a single fixed-bed reactor. The started reaction was conducted at the temperature of 380℃, 3.5 MPa of pressure, WHSV = 1 h~(-1), and H_2/wax = 0.12 wt/wt Acidities of the catalysts were determined by TPD-NH_3, and the results indicated that the SA-0.4 sample had the highest yield of middle distillate and a promising conversion rate that had a good relation with the strength of the medium acid sites. TEM showed that metal was dispersed very well on the supports using the organic matrix combustion method. Further, SA-0.4 supports were modified with H-β and HZSM-5 zeolites materials and were prepared with different reaction conditions. The prepared supports were denoted as β-SA-y and HZSM-SA-z, respectively, where y and z represent the weight percentage of ft zeolite and HZSM-S zeolite. It was found that β-SA-0.2 had comparable results with SA-0.4 samples, while the reaction temperature was 60℃ lower. The HZSM-SA-z series catalysts showed higher activity, whereas the selectivity of middle distillates was significantly lower, and the yield of gas was too high.