Study On The Preparation Of Cyclohexanol By Direct Hydration And Indirect Hydration Of Cyclohexene

Cyclohexanol is an important organic chemical intermediate and has been widely used in many fields.The process of preparing cyclohexanol by hydration of cyclohexene is a green,economic and safe synthesis process,which has important practical significance and good application prospects.At present,the cyclohexene hydration process mainly uses HZSM-5 molecular sieve as the catalyst.The process has high product selectivity and the catalyst is easy to be separated.However,due to the low solubility of cyclohexene in water,the conversion of the reactants is low,and the yield of cyclohexanol is low.Therefore,improving the conversion of cyclohexene and the yield of cyclohexanol is the research focus of this subject.The thesis conducted a systematic study on cyclohexene indirect hydration and direct hydration to prepare cyclohexanol.The main conclusions are as follows:Firstly,the synthetic route of cyclohexene indirect hydration to cyclohexanol was tried,using a two-step process,that is,the first step was to synthesize cyclohexyl methyl ether through the addition reaction of methanol and cyclohexene,the second step was to generate cyclohexanol from the reaction of cyclohexyl methyl ether with water The effects of different catalysts on the addition reaction of cyclohexene with methanol and the hydrolysis reaction of cyclohexyl methyl ether were investigated,and the reaction conditions were optimized.The results show that the HZSM-5molecular sieve shows good catalytic activity in both reaction systems.In addition reaction of cyclohexene with methanol,the optimal reaction conditions were that the reaction temperature was 130 ?,reaction time was 8 h,mass fraction of catalyst was15%,stirring speed was 900 rpm,methanol to cyclohexene molar ratio was 15:2,At this time,the conversion of cyclohexene reach 70.0%,the selectivity of cyclohexyl methyl ether was as high as 94.7%,and the yield of cyclohexyl methyl ether was66.2%.In the hydrolysis reaction of cyclohexyl methyl ether,the optimal reaction conditions were that the reaction temperature was 120 ?,reaction time was 3 h,mass fraction of catalyst was 12%,stirring speed was 900 rpm,mass ratio of cyclohexyl methyl ether to water was 1:5.At this time,the conversion of cyclohexyl methyl ether was 39.4%,the selectivity of cyclohexanol was 37.5%,and the yield of cyclohexanol was 14.8%.Higher than the yield of cyclohexanol from Asahi Kasei(9%?10%).Secondly,in order to further improve the yield of cyclohexanol,The two-step synthesis method was changed to one-step synthesis method for cyclohexanol preparation That is,methanol was added during the hydration process of cyclohexene,and the process for preparing cyclohexanol by this hydration method is explored.Using HZSM-5 molecular sieve as catalyst,the optimal reaction conditions were investigated.The results show that the reaction temperature was 120 ?,reaction time was 4 h,mass fraction of catalyst was 12.8%,the molar ratio of methanol to cyclohexene is 8:1,the volume ratio of cyclohexene to water was 2;5 and stirring speed was 1000 rpm Under the reaction conditions,the conversion of cyclohexene reach 61.8%,the selectivity of cyclohexanol was 37.3%,the selectivity of cyclohexyl methyl ether was 62.7%,and the yield of cyclohexanol reach 23.1%,the yield of cyclohexanol was significantly improved.The stability of the HZSM-5 molecular sieve was investigated.The results show that the activity of the catalyst decreases with the increase of the number of times of use,and the activity of the catalyst recovers after the catalyst is calcined,indicating that the HZSM-5 molecular sieve catalyst can be used repeatedly.