Research On The Catalysts For Preparation Of Liquid Fuels Through Hydroisomerization And Hydrocracking Of Bio-paraffin

In recent years,the energy crisis and the environmental crisis are seriously exacerbated by the over-exploitation of fossil fuels of the human.To solve these problems,renewable bio-fuels produced from animal fats,illegal cooking oil and biomass energy,including vegetable oil,fatty acid,algae,palm oil,are focused by our society.The purpose in this paper is to produce liquid fuels through hydroisomerization and hydrocracking of bio-paraffin obtained from hydrodeoxygenation of illegal cooking oil using SAPO-11 zeolite as a catalyst.Transformation of n-bio-paraffin into branched isomers will decrease the ice point of aviation kerosene,which means a lot to the energy saving and emission reducing.The Pt/SAPO-11 and the composite molecular sieve catalyst Pt/SAPO-11+ZSM-5 were prepared by incipient-wetness impregnation method and characterized by X-ray diffraction（XRD）,BET and NH₃-TPD.The effects of calcination temperature,calcination time,Pt loading,reaction temperature,space velocity,reaction pressure and hydrogen-oil ratio on Pt/SAPO-11 were investigated.The acid content and acid strength of Pt/SAPO-11+ZSM-5 were adjusted by adding different silica-alumina ratio and amount of ZSM-5 molecular sieve,and the performance of Pt/SAPO-11+ZSM-5 on bio-paraffin was studied.The main content as well as the achieved conclusions is as follows:（1）Under the calcination temperature of 500℃and the calcination time of 3h,the catalyst precursor could effectively decompose into Pt metal,and it shows high catalytic activity of hydroisomerization and hydrocracking of bio-paraffin on Pt/SAPO-11.（2）The increasing of Pt loading will enhance the catalytic activity of Pt/SAPO-11.The best Pt loading of the Pt/SAPO-11 is 0.7%.（3）Under the conditions of 0.7%Pt loading with SAPO-11,temperature of 380℃,pressure of 2.5 MPa,LHSV of 1 h^-1,hydrogen-oil ratio of 1000:1,oil yield had reached 52.2%and the selectivity of mono-branched isomers was 61.6%,along with middle/light distillates ratio of 1.57.（4）To optimize the catalytic performance,composite molecular sieves of SAPO-11+ZSM-5 with different Si/Al ratios were prepared by physical mixing.The acid content,acid strength on surface of catalyst was adjusted to achieve a balance of the acid content and acid strength by adding different silica-alumina ratio and amount of ZSM-5 molecular sieve.With the ZSM-5（300）dosage of 3%wt in the composite molecular sieves catalyst,it decreases the optimal reaction temperature to 360℃,with the oil yield of59.9%,the selectivity of mono-branched isomers of 59.7%and middle/light distillates ratio of 1.03.（5）The result of aviation bio-fuel demonstration project shows that Pt/SAPO-11 catalyst has good hydroisomerization and hydrocracking performance.