Preparation Of Nanosized Molecular Sieve And Its Application In The Synthesis Of Organic Esters

Organic carboxylic ester is an important kind of chemical product andpharmaceutical intermediate. Esterification is one of the organic chemical reactionswhich need the existence of catalysts. Performance of catalysts will effect greatly on theprogress conditions of operation in production, yield and quality of products andpost-reaction treatment of products. Being as an esterifying catalyst with highperformance, it should have enough mechanical strength and is easily separated fromfinal products, it also should be cheap in price and easily available and have nocorrosion and pollution, in addition to high catalytic activity and good catalyticselectivity. Since the last ten years, studies on using zeolite molecular sieve as catalystin esterification reaction are very popular both at home and abroad. In such reactions,the post-reaction treatment is simple, the catalyst can be regenerated and mild infunction and is poisonousless.Size of grain is a key parameter which effect largely on the performance of zeolitemolecular sieve. Compared to the microsized zeolite molecular sieve, the nanosizedZSM-5has more advantages, for example, larger specific surface area, high surfaceenergy, short pore canal, etc,especially HZSM-5. Since nanosized zeolite molecularsieve has more specific surface area, surface acidity of HZSM-5is enhanced greatly,which benefits to acid catalyzed reactions.In this study, factors contributing to the synthesis of ZSM-5by hydrothermalsynthesis method are investigated, including template, crystallization temperature,alkalinity, ratio of Si and Al, degree of saturation of the reaction mixture. Theexperimental result shows that ZSM-5with grain size of200nm can be synthesizedsuccessfully in a synthesis system in proportion of SiO₂:Al₂O₃:Na₂O:EDA:H₂O＝40:1:9.6:36:1400at the crystallization temperature of150℃by static hydrothermalsynthesis method while taking ethylene diamine as template and silicasol as Si source.After aged for24hours at room temperature, the system is placed in an oven and crystallized at100℃for12hours. Then rise the temperature to150℃. ZSM-5withhigh crystallinity can be synthesized after6hours.In this paper, we also investigated the acid catalysis performance of HZSM-5. Theroasting temperature of HZSM-5was determined by TPD characterization method.Experimental results of esterification using HZSM-5showed that, the catalyzing effectof HZSM-5to aliphatic carboxylic acid esters is far better than it to aromatic esters.