Study Of Synthesis And Catalytic Properties Of Zeolites L Formed In Polyacrylamide Hydrogels

Nowdays, study and development of long-chain n-paraffins hydroisomerization catalyts plays an important role in the productions of high-quality diesel and lubricant. The results show that Pt/SAPO-11catalyst with Weak acid and one-dimensional10-ring straight channel has the highest isomerization selectivity and has excellent performance on the isomerization dewaxing aspect of production of low pour point and high viscosity index lubricants. Zeolite L and SAPO-11have a similar one-dimensional pore structure, but zeolite L can not be used in the hydroisomerization of long-chain n-paraffins, because it has too much alkalescence cations and strong acid. Therefore, it is very important and significance for its isomerization reaction to decrease the alkalescence cations, adjust the acidity and optimize the pore structure by proper modification methods.In this thesis, grain size and acidity of zeolite L were regulated by synthesis or modification. The relations of the results of n-dodecane hydroisomerization reaction on Pt/HL and their grain size and acidity were studied.The effect of Polyacrylamide gel on the zeolite L synthesis was investigated by changing the amount of polyacrylamide hydrogel. The experimental results show that there was a significant impact of the amount of polyacrylamide hydrogel on the crystal morphology and crystallinity of zeolite L, and the crystallinity was also influenced by the mixing time of the gel. In the total mass of the gel, the optimal amount of polyacrylamide hydrogel is2%.The zeolite L was modified by ion-exchange, calcination at high temperature, citric acid and aluminum sol processing. Studies have shown that shortening the time of ion exchange could reduce the acidity of the zeolite L, comprehensive treatment of the ion exchange and hydrothermal calcination was not conducive to the retention of the zeolite crystal morphology, the addition of appropriate amount aluminum sol would improve the ratio of the strength of acidic centers in the catalyst amount becacse of the reducing of the acidity and the grain size of the catalyst, the addition of the appropriate amount citric acid adjusted the acidity of the catalyst and improved the performance of the catalyst for the isomerization, the mass ratioes of L-zeolite and alumina sol, Citric acid are1:0.75and1:0.22.The effects of reaction temperature, hydrogen partial pressure, WHSV and H2/hydrocarbon molar ratio on hydroisomerization reactioninspection of Pt/HL and Pt/SAPO-11catalysts were studied. The process optimization conditions of n-dodecane hydroisomerization reaction on the Pt/HL modified were determinated. A78.5%selectivity of iso-dodecane has been archived at a79.7%conversion of n-dodecane at340℃(hydrogen pressure=2MPa, H2/C12molar ratio=15and WHSV=1.0h-1). Under the optimum conditions, the effects of Series of modification of Pt/HL catalysts on hydroisomerization reaction have been studied and were compared with experiments of Pt/SAPO-11catalyst. The results confirmed that the isomerization performance of catalyst designed had been significantly improved. In the suitable polyacrylamide system, suitable conditions of ion exchange and hydrothermal calcination and the addition of appropriate amount alumina sol and citric acid could improve its product distribution of n-dodecane hydroisomerization reaction.