Study on Catalytic Reaction Process for Synthesis of Cyclohexanol from Hydration of Cyclohexene
|School||East China University of Science and Technology|
|Keywords||Cyclohexene hydration HZSM-5 An ion exchange resin Reaction kinetics Solvent effect|
Cyclohexanol Preparation cyclohexene liquid water is an economic and practical green technology, and is conducive to the sustainable development of human society. Ion exchange resin and HZSM-5 zeolite, but the study on the adsorption behavior of the reaction system and the reaction mechanism has not been reported as two different solid catalytic materials have been widely used in the hydration reaction of cyclohexene, which For a more clear understanding of the hydration reaction of cyclohexene has important significance. The study for the first time based on the reaction mechanism of the Langmuir-Hinshelwood-Hougen-Watson (LHHW) reaction mechanism and the Eley-Rideal (ER), respectively, derived three heterogeneous kinetic model to identify the two catalysts cyclohexyl alkylene hydration reaction mechanisms: (1) adsorption of the reaction between cyclohexene with the adsorbed water model; (2) the reaction between the adsorbed water phase cyclohexene model; (3) Adsorption of cyclohexene The model of the reaction between the water phase. The dynamics study results show that heterogeneous kinetic model showed the ability to fit the experimental data comparable to the homogeneous kinetic model is more satisfactory. Based on the kinetic results and infrared spectroscopy can determine HZSM-5 zeolite catalytic cyclohexene hydration reaction is to follow the reaction mechanism of ER, water molecules adsorbed on HZSM-5 zeolite activity center first form hydronium hydronium ion substitution Bronsted acid centers cyclohexene molecules direct reaction to obtain a product of cyclohexanol as the new active centers with adjacent body phase. HZSM-5 catalytic cyclohexene hydration reaction activation energy is 77.69 kJ / mol, water and cyclohexyl alcohol adsorption equilibrium constant of 19.95 and 146.6 respectively. HZSM-5 zeolite catalysts, ion exchange resin catalyzed cyclohexene The hydration reaction followed the LHHW mechanism, first cyclohexene adsorbed molecules in the active center of the resin catalyst to form a carbocation, and then to react to obtain a product of cyclohexanol and adsorbed water molecules. The ion exchange resin catalyst of the hydration reaction of cyclohexene activation energy of 79.92 kJ / mol, cyclohexene, water and cyclohexanone, alcohol adsorption equilibrium the constants were 6.745,24.30 and 81.91. Can be found, the activation energy of a cyclohexene hydration reaction on the two catalysts difference is not large, which indicates that different mechanisms Although the two catalyst catalyzed cyclohexene hydration reaction, but its catalytic hydration reaction of itself little difference between the energy barrier. Examines the solvent effect of the different organic co-solvent for the hydration of cyclohexene in the batch autoclave. The results showed that, compared to the resin catalyst, the role of the organic co-solvent is added to HZSM-5 catalyst, the hydration reaction of cyclohexene is more obvious. The first time in this study the co-solvent is ethylene glycol for the HZSM-5 catalyst of the hydration reaction of cyclohexene exhibit the best solvent effect, certain conversion of cyclohexene under the reaction conditions, from 8.2% to 11.4%. In order to evaluate the ethylene glycol under cyclohexene solubility in the aqueous phase exists at 298.15 K cyclohexene water cyclohexanol glycol four component coexisting liquid-liquid equilibrium system, the results show that a modified UNIFAC group group contribution method can be used to more accurately fit the liquid-liquid equilibrium data. Further kinetic results show that the HZSM-5 catalyst, the hydration reaction of cyclohexene reaction mechanism has not changed because the co-solvent of the glycol added, and the reaction is still followed ER reaction mechanism. However, due to the adsorption equilibrium constant of the the glycol solvent effect, the activation energy for the hydration reaction of cyclohexene, water molecules, and cyclohexyl alcohol molecule have suffered a certain degree of reduction. Trimethylchlorosilane modification of the outer surface of HZSM-5 zeolite as a surface modifier, lipophilic and amphiphilic HZSM-5 zeolite. The surface modification is effective in improving the HZSM-5 zeolite oleophilic outer surface, and improve the catalytic activity of the catalyst for the hydration reaction of cyclohexene. Experimental results show that the amount of trimethylchlorosilane, amphiphilic HZSM-5 zeolite prepared by the catalytic activity for the hydration reaction of cyclohexene is preferably 0.4 mL / g cat. Also investigated the influence of the catalytic activity for the hydration of the different pretreatment methods. Resin catalyst in the pre-reaction after water or cyclohexene after pretreatment showed a poor catalytic activity. However, the catalytic activity of HZSM-5 zeolite after water pretreatment has been significantly improved, under the same reaction conditions, the cyclohexene conversion rate increased from 6.4% to 7.3%; cyclohexene pretreated HZSM-5's catalytic activity than many differential without pretreatment, which should be caused HZSM-5 catalyst deactivation due to the pretreatment process. Also, for the first time the ultrasound is introduced into a cyclohexene hydration reaction system, experimental results show that the ultrasonic power is 900 W ultrasonic for the HZSM-5 catalyst of the hydration reaction of cyclohexene having the best role in promoting a certain reaction conditions under cyclohexene conversion rate from 6.1% to 8.6%, the ultrasonic power is too low to provide enough hole bubbles, ultrasonic power is too high will limit the ultrasonic energy transfer.