Study On The Process Of Hydration Of Cyclohexene By HZSM-5 Zeolite

As an important organic chemical material, Cyclohexanol is an necessary intermediate to produce caprolactam and adipic acid which are useful amide products.As to the traditional methods of producing cyclohexanol, there are a variety of shortcomings in some aspects such as cost, energy consumption, safety and environmental protection. Preparation of cyclohexanol by cyclohexene hydration has many advantages in simpler process, less waste and environmental protection,which lead good application prospect. HZSM-5 zeolite is one of the catalyst used widely for cyclohexene hydration currently because of the uniform pore channel, good shape selective catalyst performance,high thermal stability and appropriate acid, however, the selectivity of cyclohexene on HZSM-5 is low. In this paper, we studied cyclohexene hydration on HZSM-5, and prepared HZSM-5 modified by pHospHotungstic acid and with no template, explored the relationship between the properties of catalyst and reaction.At first, we prepared the HZSM-5 zeolite modified by phosphotungstic acid and discussed the effects of the phosphotungstic acid content, calcination temperature and calcination time on the reaction about hydration of cyclohexene reaction. Then, we characterized the different catalysts,concluded that phosphotungstic acid could be well dispersed on the surface of HZSM-5 after modifying as well as the content of bronsted acid and lewis acid changed. When the loading content of phosphotungstic acid is 40%,the calcination temperature is 350?, and the calcination time is 4 hour, the activity of catalysts was the best,and we concluded that the increasing amount of bronsted acid can promote the hydration of cyclohexene.The hydration of cyclohexene using 40%HPW/HZSM-5(calcination temperature is350?, calcination time is 4 hour) as catalyst was optimized. The best reaction conditions were obtained. Reaction temperature is 120?, time is 6 h, pressure is 0.6 MPa, stirring speed is 900r/min, the catalyst content is 30%, the volume ratio of cyclohexene to water is2:5, the conversion of cyclohexene was 15.0% and the selectivity to cyclohexanol was up to 99.3%, and the yield of cyclohexanol was 14.9% which increased about 4% compared with HZSM-5 before modifying.The studies on preparation of HZSM-5 without template was carried show that HZSM-5 zeolite with good crystallinity can be prepared under these conditions: using ludox and TEOS as silicon source, crystallization time is 24h~72h, crystallizationtemperature is 180 ?, molar ratio of Si2 O to Al2O3 is 20~50, system pH is 10~10.5, molar ratio of H2 O to Si2 O is 25~45.The best reaction activity of cyclohexene hydration using HZSM-5 zeolite with no template could be obtained under these preparation conditions of catalyst: silicon source is ludox, aluminum source is sodium metaaluminate, molar ratio of materials is25SiO2:1Al2O3:625H2O, system pH is 10. In these conditions, the zeolites had high crystallinity, suitable hydropHily, appropriate acid and high bronsted acid, the conversion of cyclohexene was 12.7%, the selectivity to cyclohexanol was 99.2%, and the yield of was cyclohexanol was 12.6%.