Effect Of Organic Solvent On The Activity Of Cyclohexene Hydration

The liquid-phase cyclohexene hydration to produce cyclohexanol is an atom economicreaction. It can be a clean production by developing solid catalyst. However, this process suffersfrom the low cyclohexanol yield. Effect of morphology and particle size of HZSM-5, organicsolvent and reaction conditions on the activity of cyclohexene hydration was studied in thispaper.Firstly, HZSM-5 zeolite was synthesized by dynamic hydrothermal synthesis method. X-raydiffraction (XRD) characterization results showed that the crystallinity of HZSM-5 was high.Effects of molar ratio of silica to alumina, pH regulators, crystallization temperature, surfactantsand crystallization time on morphology and particle size of HZSM-5 were represented byscanning electronic microscopy (SEM) characterization. HZSM-5 with high molar ratio of silicato alumina had more regular morphology. The pH regulators had little influence on morphologyand particle size of HZMS-5. HZSM-5 with more regular morphology and smaller particle sizecould be prepared by varying-temperature synthesis method. The monodisperse HZSM-5 shapedlike cakes was synthesized with suitable surfactants as additives. The average particle size was0.5μm. The particles would grow up to 3.0μm with the crystallization time prolonged. Themonodisperse HZSM-5 shaped like cakes with small particle size showed excellent catalyticactivity on cyclohexene hydration.Secondly, the reaction conditions of indirect cyclohexene hydration catalyzed by sulfuricacid were optimized. Under the optimal reaction conditions: sulfonation time 1h, molar ratio ofsulfuric acid to cyclohexene 3:1, concentration of sulfuric acid in hydrolysis 25%(wt%) andsulfonation concentration of sulfuric acid 85%, the cyclohexene conversion was 70.7%, and thecyclohexanol selectivity was 97.9%. Phosphotungstic acid showed more excellent catalyticactivity in the system of cyclohexene hydration catalyzed by heteropoly acid. Effect of differentkinds of organic solvents on the activity of cyclohexene hydration catalyzed by phosphotungsticacid was researched for the first time. Effect of phase transfer catalysts on the activity ofcyclohexene hydration was researched with actone as solvent. The reaction conditions wereoptimized by the orthogonal experiments. Under the optimal reaction conditions: volume ratio ofcyclohexene to water 2:3, volume ratio of water to acetone 1:1, concentration of phosphorus acid 0.005 mol/L, reaction temperature 180℃, and reaction time 2 h, the cyclohexene conversionwas 16.0%, and the cyclohexanol selectivity was 100%.Lastly, effect of various organic solvents on the activity of cyclohexene hydration withHZSM-5 zeolite as catalyst was studied, and the optimal organic solvent was isophorone. Underthe optimal conditions: volume ratio of isophorone to cyclohexene 4:1, concentration of catalyst15%, reaction time 3h, the cyclohexene conversion was 34.5%, and the cyclohexanol selectivitywas 99.3%. Effect of phase transfer catalysts on the activity of cyclohexene hydration withisophorone as solvent was studied. It showed that cyclohexene conversion decreased with the Bacid sites number decreasing. With the presence of isophorone, the performance of repeated useof HZSM-5 zeolites was studied for the first time. The characterization results of the deactivatedcatalyst showed that the main reasons of catalyst deactivation were the organics accumulationand the loss of framework aluminum.