Preparation Of Aviation Kerosene From Castor Oil By One-step Hydrogenation And Design Of Catalytic Materials

A series of Pt/SAPO-11 catalysts were synthesized by using incipient-wetness impregnation method with SAPO-11 molecular sieve as carrier and active mental component Pt.The properties of catalysts were changed by adding La,Ce,Sn,Fe,Co,Ni,Cu,Zn and other auxiliary agent for metal.Using castor oil as the model molecular probe,a one-step hydrogenation catalyzed continuous preparation of bio-aviation kerosene was carried out in a high pressure micro fixed-bed reactor.The effects of bimetallic multifunctional catalysts with adding auxiliary agent for metal on hydrodeoxygenation performance,the selectivity of C₈-C₁₆ alkanes,the selectivity of C₈-C₁₆ iso-alkanes and the selectivity of C₈-C₁₆ arenes were evaluated systematically.On the basis of this study,three catalysts with a good comprehensive performance,namely Pt-La/SAPO-11,Pt-Ce/SAPO-11,Pt-Co/SAPO-11,were selected for characterization with XRF,XRD,BET,TEM,H₂-TPR and NH₃-TPD.The relationship between macroscopic catalytic properties and micro structure of selected catalysts was discussed.It was found that the addition of La,Ce and Co reduced the specific surface area,pore volume and average pore diameter of SAPO-11 molecular sieve carrier,but increased the acid sites and total acid contents of the carrier,decreased the crystalline size of active component Pt and the strong interaction between Pt and the carrier.Meanwhile the Pt-La/SAPO-11 catalyst showed a perfect physicochemical property.Making the Pt-La/SAPO-11 as catalyst,the influences of temperature,pressure,liquid hourly space velocity?LHSV?and hydrogen/oil ratio?hydrogen volume/castor oil volume?on one-step hydrogenation catalytic reaction of castor oil were investigated in the fixed-bed hydrogenation reaction system.Based on the unsaturated fatty acid triglycerides as the model compound,the mechanism of one-step hydrotreatment catalytic process of animal and vegetable oil over Pt/SAPO-11 catalyst was speculated five steps:unsaturated fatty acids in triglycerides were hydrogenated to saturation,saturated fatty acids produced straight-chain alkanes by hydrodeoxygenation,straight alkanes were happened protonation,secondary positive carbon ions occurred isomerization,small molecule isomeric olefin became saturation alkanes by hydrogenation.Finally,the best operating parameters of castor oil on one-step hydrogenation catalytic reaction in a high pressure micro fixed-bed reactor were founded to be temperature at 400°C,a pressure at 3.9 MPa,the LHSV at 0.9 h^-1 and the hydrogen/oil ratio at 1000 NmL·mL^-1 by response surface methodology.The verification experiment was carried out 3 times and the selectivity of C₈-C₁₆hydrocarbons was found to be 58.76%.