Hydration Of Cyclohexene To Cyclohexanol Catalyzed By ZSM-5 Treated With NaOH

Cyclohexanol is an important chemical intermediate for the production of adipic acid and caprolactam.Currently,cyclohexanol is mainly produced by means of cyclohexane oxidation.However,this method suffers from some disadvantages,such as the danger of explosion and high energy consumption.As the success of benzene partial hydrogenation to prepare cyclohexene developed by Asahi Chemical Industry Co.,Ltd.,cyclohexanol manufacture through cyclohexene hydration has been paid great attention.ZSM-5 zeolite is the major catalyst for the hydration of cyclohexene to cyclohexanol.However,apart from the high cost of ZSM-5 preparation,the raction of the hydration of cyclohexene to cyclohexanol catalyzed by ZSM-5 has the problems of low cyclohexene conversion and the slow reaction rate.Thus,it is a great need to develop an inexpensive synthetic route for ZSM-5 zeolite and appropriately modify the ZSM-5 zeolite to increase the hydration rate of cyclohexene to cyclohexanol.In this work,ZSM-5 zeolite was synthesized by a hydrothermal method with the addition of ZSM-5 zeolite as seeds,and the effects of the seed amonts on the textural properties of ZSM-5 and the catalytic performance has been studied.The results indicated that the amounts of acid sites,specific surface areas and mesoporous volumes of ZSM-5 increased with increasing the amounts of seeds;the synthesized ZSM-5 zeolite with the addition of 8 wt.% seeds showed the best catalytic performance.In addition,ZSM-5 prepared with the addition of 8 wt.% seeds was treated with NaOH to improve the conversion of cyclohexene,and the effects of treatment tempertures,treatment times and NaOH concentrations on the catalytic performance have been systematically investigated.The results showed that the treatment of ZSM-5 zeolite with low NaOH concentrations can lead to the creation of some mesopores in the ZSM-5 zeolite,resulting in an increase of the cyclohexene conversion because the reactants and products can diffuse more easily in the zeolite channels.The optimal NaOH treatment conditions are NaOH concentration of 0.2 mol/L,treatment temperature of 85 oC and treatment time of 2 h.