The Preparation Of Rare Earth Metal And Si-modified Alumina As The FCC Matrix And Its Application In The Catalytic Cracking Of Heavy Oil

With the heavy and inferior crude oil,as well as increasingly stringent environmental development requirements,the performance requirements for FCC catalysts become more demanding.FCC catalysts require good stability,high product selectivity and good resistance for vanadium contamination.For the FCC catalyst,the matrix component accounts for approximately 70%.The main role of matrix component is to support the active components of the catalyst,providing a pre-cracking site,which directly affects the diffusion and reaction path of the reactants during the reaction.Therefore,under the general trend of heavy oil refining and refining in the world,the development of new and efficient matrix materials is very important.Firstly,this paper adopts Na Al O₂-Al₂(SO₄)₃ method,and introduces sodium silicate and rare earth chloride to synthesize modified alumina matrix in the preparation process.The experimental results show that the silicon-modified alumina material has a high specific surface area and a large pore volume.It was confirmed that sodium silicate can be used as a pore-enlarging agent to enrich the pore structure of the matrix material.However,after high-temperature calcination,the specific surface area and pore volume of the matrix material modified only with silicon are decreased,and the alumina material modified by the combination of silicon and rare earth elements can maintain a large specific surface area and pores volume at high temperatures.By optimizing the synthesis conditions,when the synthesis temperature is 90 ^oC,Al O₂^-/(RE³⁺+Al³⁺)=2.5,RE/Al=0.005,the specific surface area of the matrix are>450m²/g,and the pore volume are>1 cm³/g.Further explore the crystal structure of the modified matrix.The results show that the alumina matrix material modified by rare earth element and silicon is still dominated by?-Al₂O₃form at 1200^oC,while pure alumina has been completely converted into?-Al₂O₃.Under hydrothermal aging conditions,the modified alumina matrix is?-Al₂O₃,and the pure alumina is transformed into?-Al₂O₃,indicating that the modified matrix have good thermal stability and hydrothermal stability.Secondly,the heavy oil conversion ability and vanadium resistance ability of modified alumina as catalytic cracking catalyst matrix were investigated.The catalytic cracking catalyst was prepared by selecting a suitable matrix material to investigate the effect of rare earth element content on the reaction direction,conversion rate and selectivity of catalytic cracking.The results show that the diesel yield,liquefied gas yield and conversion rate are the optimal values when the amount of cerium is appropriate(Ce/Al=0.005),and the amount of dry gas is also reduced.However,the content of rare earth elements that are too high or too low will cause a decrease in conversion rate.It shows that the effect of improving the performance of catalytic cracking reaction can be achieved only when the rare earth element is in an appropriate amount.The results show that after vanadium pollution and hydrothermal treatment,the catalytic cracking catalyst synthesized by using cerium modified alumina as the matrix,the crystal structure of the zeolite and the pore structure of the catalyst are more stable.