Study On Isodewaxing Catalysts Enduring Sulfur And Nitrogen Compounds

The rapid development of industry has greatly promoted the technological progress of the lubricating oil industry and the upgrading of product quality.Isodewaxing technology,which replaced the solvent dewaxing technology,has moved into the mainstream.At present,the isomeric dewaxing catalysts that used in industry are noble metal/molecular sieve catalysts.In order to prevent the poisoning from the precious metals and prolong the service life of the catalyst,the requirements of the sulfur and nitride content of the raw materials are extremely harsh.Consequently it is important that developing a catalyst with strong ability to resist sulfur and nitrogen.For the catalysts,unique pore structure and acidity should be choosed,in the meantime,appropriate active component must be selected and optimized.In this paper,SAPO-11-based isomerization dewaxing catalysts were modified and trasition metal nitride/SAPO-11 catalysts were prepared.Then the heterogeneous dewaxing and sulfur and anitrogen tolerant of the catalyst were investigated by using the mixed fuel of hydrocracking tail oil and second-line wax oil as raw material.First of all,SAPO-11 molecular sieves were prepared by dynamic hydrothermal synthesis.The initial gel composition(molar ratio)was 0.3-3.0Si O2: 1.0Al2O3: 1.0P2O5: 0.8-1.6 di-n-propylamine: 55H2 O,and crystallization time was 24-60 h to prepare SAPO-11 molecular sieve.Compared with the traditional static hydrothermal synthesis of SAPO-11 molecular sieve properties,the results show that the dynamically synthesized molecular sieves not only are pure phase SAPO-11 crystals with a grain size of only 1/5 of the conventional hydrothermal synthesis of SAPO-11 grains,but also possess higher silicon content,which means more Bronsed acid and Luise acid sites,and more microporous specific surface.Moreover,SAPO-11 by dynamic synthesis method also are synthesized in a 2L autoclave that is close to the industrial production requirements.Secondly,the small grains SAPO-11 were mixed with pseudo-boehmite to obtain extruded catalyst carriers,and then Ni and W were loaded in them to prepare oxidation state catalysts.Next,to develop isodewaxing catalysts,the oxidation state catalysts were be presulfurized,reduced and nitrided,respectively.The catalysts were evaluted in a 50 ml fixed bed reactor.The result showed that the hydrogenation ability of the nitrided catalyst was better than others.Furthermore,the effects to nitriding conditions on the formation of nitrides and the performance of isotactic dewaxing of Ni-W nitride catalysts were investigated.Through the analysis of the catalyst and the evaluation of the reaction performance,it can be seen that the nitrification space velocity and nitriding time will affect the surface nitrides of the catalyst,and when the space velocity is large,the hydrothermal sintering of the nitride is avoided,the distribution of active ingredients is much uniform,and achieve higher nitride content.The prolongation of nitriding time is not conducive to the increase of the nitride content of the catalyst,and the isomerism dewaxing activity of the catalyst is positively correlated with the nitrogen content of the catalyst.Therefore,the use of large space velocity,short-term nitriding method to improve the catalyst isomerization dewaxing activity is more favorable.Subsequently,the mixing of hydrocracking tail oil and the vacuum second-line wax oil in different proportions was taken as the raw material,and the sulfur and nitrogen toleration performance of the catalyst was evaluated.It was found that the nitrification catalyst had better resistance to sulfur and nitrogen.When the content is less than 200?g / g and the nitrogen content is less than 100?g / g in raw material,the activity of the catalyst is almost unaffected.In addition,Ni-Mo-W three metal nitrides SAPO-11 catalyst and Ni-Mo bimetallic nitride SAPO-11 catalyst were prepared under the optimal nitriding conditions.The active components of Ni-W nitride catalyst and Ni-Mo nitride catalysts were determined by XRD.For Ni-Mo nitride catalyst,the nitrides on the surface of the catalyst are mainly Ni2Mo3 N.It can be concluded from the reaction evaluation that the base oil product,Ni2Mo3 N as the active component is the best.Considering the properties of base oil and the operating cost of equipment,the optimum nitrification type is Ni2Mo3 N,The nitriding conditions were as follows: temperature 700 ?,space velocity 1500h-1,hydrogen nitrogen gas volume ratio 5: 1,nitriding time 90 min.The optimum reaction conditions were as follows: reaction pressure 15 MPa,reaction temperature 390 ?,space velocity 0.8h-1,hydrogen / oil ratio 1000: 1.At this point,the product base oil pour point was-27 ?,the yield was 66.4%,and the viscosity index was 102.