Preparation Of Bio-Jet Fuel By Long-Chain Alkanes

In recent years,due to the rapid development of aviation and the growing awareness of environmental protection.The issue of aviation emission reduction has been paid attention by countries around the world.Bio-aviationfuels are favored by national airlines by virtue of their recyclability and the ability to effectively mitigate greenhouse effects.Therefore,the technology of preparing high-quality bio-aviation fuels by hydroisomerization of the long-chain alkane that produced from oils has been taken seriously.In the process of hydroisomerization,molecular sieves are usually used as catalyst supports.SAPO^-11 molecular sieve has suitable pore size,as well as the weak center of the strong acid.It has obvious advantages in hydroisomerization and was often used as a supports for the hydroisomerization of long-chain alkanes.In this paper,long-chain alkanes prepared by deoxidization of fatty acid methyl esters were used as the feedstock for hydroisomerization,and SAPO^-11 molecular sieves that loaded by nobel metal were taken as catalyst for hydroisomerization.The research work is as follows:The hydrothermal synthesis of molecular sieves SAPO^-11 was carried out using pseudoballite,phosphoric acid,acid silica sol and di-n-propylamine?DPA?as materials.The effects of Si/Al ratio?0.1?0.3?0.5?0.7?,crystallization temperature?150?170?180 ??and crystallization time?24?36?48 h?on preparation of SAPO^-11 were investigated.The properties of preparation of SAPO^-11 were characterized by XRD,BET,SEM and NH3-TPD.The characterization results indicated that: The Si/Al ratio was 0.3,the zeolite got higher crystallinity and the number of impurity was less.Under the condition of high temperature,the crystallinity of the crystals is relatively high,along with the particles are larger.On the contrary,the crystal growth rate decreases at lower crystallization temperature,which results in the decrease of grain size.SAPO^-11 zeolite can be completely crystallized within 24 h,more than 24 h the other crystals will appear.With the increase of Si/Al ratio,molecular sieves has the larger specific surface area and the pore volume as well as the specific surface area and pore volume decreased gradually.There were a weak acid and strong acid sites in SAPO^-11.The molecular sieve was regular morphology,uniform particle size,less impurity.with crystallization temperature of 180 ? and crystallization time was screened out by characterization.The 0.5%Pt/SAPO^-11 catalyst was prepared by equal volume impregnation method by using the molecular sieve with different Si/Al ratios as the carrier under this crystallization temperature and crystallization time.Then n-octadecane was used as a model compound to test the isomerization reaction.It is found that when the Si/Al ratio was 0.3,the isomerization performance was better.Then oil yield reached 73.1%,and the hydroisomerization rate was 64.2%,along with middle/light distillates ratio of 1.44.Preparation of octadecane by deoxidization of C18 fatty acid methyl esters.The catalytic activity of 0.5%Pt/SAPO^-11?0.3,180 ?,24 h?catalyst was test by using the conversion rate,the middle/light distillates ratio and the rate of isomerization.At the same time,the effects of reaction temperature,reaction pressure,space velocity and ratio of hydrogen to oil process conditions on the reaction results were investigated.The result showed: at the temperature of 340 ? the pressure of 3 MPa,space velocity of 1 h^-1 and hydrogen oil ratio of 1000:1,oil yield had reached 73.1%,and the hydroisomerization rate was 64.2%,along with middle/light distillates ratio of 1.44.The hydrocracking isomerization of Pt / SAPO^-11 and Pt / ZSM-5 was compared.In this paper,Pt/ZSM-5 was used as catalyst for hydroisomerization.Mainly compared Pt/SAPO^-11 with Pt/ZSM-5 of the product distribution at different reaction temperature,reaction pressure The results show that the isomerization performance of Pt/SAPO^-11 was better than that of Pt/ZSM-5.When the other conditions were the same,the isomerization rates of Pt/SAPO^-11 and Pt/ZSM-5 were 61.2% and 58.9%,at the temperature of 340 ? and pressure was 3 Mpa.Using Pt/SAPO^-11 as catalyst,the isomerization rate of kerosene is higher.