Synthesis And Reaction Study Of Gasoline Fraction Hydro-upgrading Catalyst

In terms of technology availability,the traditional hydro-upgrading technique is a major process for the production of clean gasoline.While deep desulfurization of FCC gasoline can be accomplished via the hydrorefining technique,the excessive olefins saturation is unavoidable,giving rise to severe octane loss.It has been widely recognized that developing and preparing novel hydroisomerization and aromatization catalysts for the FCC gasoline fraction after desulfurization,which can reverse the octane value,becomes an effective way to produce ultra clean and high octane value gasoline.In recent years,the hierarchical zeolites have attracted comprehensive attentions,the hierarchical ZSM-5/MCM-41 zeolite which combines with the high shape selectivity of microporous ZSM-5 zeolite and the excellent mass transport of the mesoporous MCM-41 material,has a potential application in FCC gasoline hydro-upgrading process.However,the conventional method exhibits complex steps and low yield in synthetic process.Therefore,the exploratory preparation of the hierarchical ZSM-5/MCM-41 zeolite possesses important signification.Based on the investigation of the synthesis conditions of the hierarchical ZSM-5/MCM-41 zeolite by the conventional alkali-treated method,this paper researched that the hierarchical ZSM-5/MCM-41 zeolite which were hydrothermally synthesized by the introduction of template and new silica-alumina species in the alkali-treated ZSM-5 seriflux,and the samples were characterized by XRD,N2 adsorption/desorption,FT-IR,NH3-TPD and HRTEM.The results showed that the optimal condition was: the ZSM-5 zeolite was alkali-treated with 1.0 mol/L NaOH solution at 80 ℃ for 1h,appropriate amount 4.76 wt %CTAB solution and the new silica-alumina sources with n(Si)/n(Al)=50 were added into the solution,the pH of gelatum of admixture is 10.0.The dynamic crystallize at 120 ℃ for 48 h.The character results indicated that the hierarchical ZSM-5/MCM-41 zeolite possessed clear core-shell structure which the morphologies of ZSM-5 as the core and the morphologies of MCM-41 as the shell.Compared with the conventional alkali-treated results,the products by the introduction of new silica-alumina species method has the advantages of high product yield,concentrated mesoporous pore distribution,high acidity and hydrothermal stability.The catalyst supports were obtained by mechanical mixing of the hierarchical materias with Al2O3,then the as-synthesized catalyst supports depositing with different Ni/Mo molarratios were prepared as the hydro-upgrading catalysts through impregnation.The results showed the hydroisomerization and aromatization activities of the hydro-upgrading catalysts were closely related to the textural properties and the acid type.when the n(Ni): n(Mo)=1:2,w(Ni)=3.0 %,the catalyst exhibited good hydroisomerization and aromatization abilities.Focus on this catalyst,the effects of reaction temperature,pressure,liquid hourly space velocity(LSHV),volumetric H2/oil ratio on the hydro-upgraded FCC gasoline compositions were investigated.The results showed that higher reaction temperature,lower pressure and lower LHSV can increase the selectivity for olefin aromatization,lower reaction temperature,higher pressure and higher LHSV can increase the selectivity for olefin isomerization,while volumetric H2/oil ratio has negligible effect.It is found that the the optimal reaction conditions were as follows:T=360 ℃,P=2.0MPa,V(H2):V(oil)=300:1 and LHSV=2.0h-1.In 72 hours time-on-stream,the olefins content in the FCC gasoline decreased from 21.68 % to 14.37 %,the olefins conversion,isomerization and aromatization product selectivity were 33.72%,57.18% and 30.37% respectively.Meanthwhile,the research octane number(RON)of the hydro-upgraded FCC gasoline increased.