Study On Preparation Of Hierarchical Y Zeolite

Fluid catalytic cracking(FCC)is an important conversion technology in petroleum refining industry,while Y zeolite,which plays a significant role,is a major active component in the catalyst of this process.However,it's hard for the micropore structure of Y zeolite to deal with the fact that crude oil is much heavier and poorer,but hierarchical Y zeolite can improve catalytic performance by raising the mass transfer efficiency and enhancing the accessibility of zeolite active centersIt can be investigated how the different amount of citric acid/citrate and NaOH,the adding sequence and the treatment time affect modified zeolite by using REUSY zeolite and NaY zeolite as raw materials,citric acid/citrate as dealumination agent and NaOH as desilication agent to broaden pores of Y zeolite by post-treatment.In the modification process of REUSY zeolite,it was found that not only the addition of different amount of citric acid/citrate and NaOH,but also different adding sequence of citric acid/citrate and NaOH did not cause obvious damage to the framework structure of zeolite.At the same time it could produce a certain amount of mesoporous.Besides,the addition of materials mentioned above could destroy the surface morphology of zeolite in different degrees When the mass ratio of citric acid/citrate to zeolite was 0.30,the prepared zeolite had the largest total specific surface area of 969m2/g,a total pore volume of 0.425cm3/g and a mesoporous volume of 0.085cm3/g.When the mass ratio of NaOH to zeolite was 0.40,the prepared zeolite had the largest total specific surface area of 946m2/g,a total pore volume of 0.438cm3/g and a larger mesoporous volume of 0.105cm3/g,and the optimized NaOH treatment time is 1 h.In the process of different addition sequence of citric acid/citrate and NaOH,by adding NaOH first and then citric acid/citrate,the results showed that the total specific surface area,total pore volume and mesoporous volume of the zeolite samples were 8 51m2/g,0.463cm3/g and 0.178cm3/g respectively.In addition,after the modification of the zeolite by adding citric acid/citrate and NaOH,the acidity of zeolites could be greatly affected.In the modification process of NaY zeolite,it was found that different adding amount of NaOH and different addition sequence of citric acid/citrate and NaOH did not significantly damage the framework structure of the zeolite.Meanwhile,the treatment could produce different degrees of mesoporous in the zeolite.Furthermore,the addition of NaOH would destroy the surface morphology of the zeolite to a certain extent.When the mass ratio of NaOH to zeolite was 0.40,the total specific surface area,total pore volume and mesoporous volume of the prepared zeolite were 914m2/g,0.396cm3/g and 0.073cm3/g respectively.Treating by adding NaOH first,then roasting and adding citric acid/citrate finally,we can got a zeolite sample with a total specific surface area of 921m2/g,a maximum total pore volume of 0.434cm3/g,and a larger mesoporous volume of 0.119cm/g,and it also had a higher micro-reaction activity index of 64%and the lowest coke yield of 7.88%.After the hydrothermal aging treatment,the zeolite which had been modified by citric acid/citrate and NaOH before,was damaged in its framework structure.And it was also found that the catalytic activity of the zeolite was closely related to its hydrothermal stability,while the acidity of the zeolite varied greatly under different adding order of components.