Research On SAPO-11 Catalyst For Isodewaxing

As the automotive industry advances and the environmental legislation becomes more and more stringent. It is regarded as an effective way to improve the quality of oil by producing high viscosity index base oil through isodewaxing process. The key to improve the isodewaxing technology is to develop an efficient catalyst. SAPO-11 molecular sieve has great hydroisomerization selectivity due to its mild acidity and monodimensional 10- member ring pore structure. And it has been widely used in industrial plant for its superiority.In the thesis, SAPO-11 was hydrothermally synthesized from an aqueous medium using the conventional method and the rapid crystallization method. Synthesis conditions such as crystallization time, crystallization temperature, template agent and silica content were studied. The XRD results showed that when the crystallization temperature was 200℃, the crystalization time was 48 h, template agent was DPA, silica source was silica sol, DPA/Al2O3 was 1.2 and Si O2/Al2O3 was 0.3, pure SAPO-11 can be synthesized. The crystallization process could be completed in 24 h with rapid crystallization method which resulted in smaller particles, uniform size and higher silica content.It was found that the molding conditions such as the amount of nitric acid and Pseudo Boehmite and the ratio of H2O/power had great influence on the catalyst strength. The condition that the amount of nitric acid of 0.4wt%, the amount of Pseudo Boehmite of 30wt% and 50wt%, the ratio of H2O/power of 30wt% was proper for molding.Then SAPO-11 synthesized by the two methods was used in the isodewaxing reaction to evaluate its performance after loading Pt. Both of them can produce high viscosity index base oils. Influence of reaction conditions including temperature and space velocity on catalysts’ performance was evaluated using a lab-scale continuous flow fixed-bed reactor. The results showed that the yield and pour point of the base oil decreased as the temperature elevated,but it went to the opposite trend when the LHSV increased. The Pt/SAPO-11 which made the best performance was picked. The reaction results showed that base oil yield can reach 75.6% with the viscosity index of 132 when the reaction temperature was 380℃, and the LHSV was 1.06h-1.The ability of catalysts to reduce the pour point was significantly enhanced when ZSM-5 was used in the catalyst system. However, severe cracking reaction and dramatic decrease in viscosity index occoured at the same time. Then ZSM-5 was regarded to be not suitable for the production of high-quality base oil.