Study On Key Technology Of Preparation Of Catechol From Epoxycyclohexane

Pyrocatechol is an important fine chemical intermediate and chemical raw material with a wide range of uses.At present,the main synthetic methods used for catechol include 2,4-disulfophenol alkaline hydrolysis,o-chlorophenol alkaline hydrolysis,o-dichlorobenzene alkali fusion,phenol hydroxylation,etc.,all of which have harsh operating conditions.,product conversion rate is low,three wastes and other shortcomings.The two-step epoxy cyclohexane preparation of catechol has low cost,high atomic economy,high yield and simple separation process.It is a synthetic route with important industrial application value and has attracted the attention of researchers.In this paper,epoxycyclohexane is used as raw material to prepare catechol by hydrolysis and dehydrogenation.The main work is as follows:??Preparation of 1,2-cyclohexanediol by hydrolysis of epoxycyclohexane?1?SO₄^2-/TiO₂-ZrO₂-La₂O₃ solid superacid,biomass carbon sulfonic acid,solid phosphoric acid and other catalysts were prepared by impregnation method.These catalysts were applied to the epoxycyclohexane hydrolysis reaction,and the main productswereobtained.Characterization;usingtheyieldof trans-1,2-cyclohexanediol as the index,the best catalyst was selected as SO₄^2-/TiO₂-ZrO₂-La₂O₃solid superacid,and was prepared by single factor experiment.The process of SO₄^2-/TiO₂-ZrO₂-La₂O₃ solid superacid catalyst was optimized.The results showed that the concentration of the immersion liquid was1.5 mol/L H₂SO₄,the concentration of La⁺was 0.04 mol/L,and the calcination temperature was 550°C.The catalysts were characterized by FT-IR,BET,ICP-OES and TG-DSC.It was confirmed that the catalyst samples showed super acidity,good mesoporous structure,excellent thermal stability and catalyst deactivation.The main reason was the loss of sulfur on the surface of the catalyst after a long period of reaction.After the deactivated catalyst is re-impregnated,the activity can be recovered.?2?The tower reactor model was designed and fabricated by itself and used for the continuous reaction of trans-epoxyhexane synthesis to trans-1,2-cyclohexanediol,and the catalytic effect of SO₄^2-/TiO₂-ZrO₂-La₂O₃ solid superacid The single-factor experiment and response surface experiment were used to study and optimize the operating conditions of the continuous process route.The optimal results were:reaction temperature 55°C,molar ratio of raw water to epoxy cyclohexane 12,mass empty After 0.8 h^-1,the yield of trans-1,2-cyclohexanediol was still above 95.6%after continuous stable reaction for 60 h.After repeated activation of the catalyst for8 times,the activity did not decrease significantly.Compared with the previous literature,the advantages of this process route were the self-made tower reactor,which had mild reaction conditions,high catalytic efficiency and long catalyst life.At 50°C normal pressure,the mass hour space velocity was 0.8 h^-1,the conversion of epoxycyclohexane was 95.9%,and the yield of trans-1,2-cyclohexanediol was 95.6%or more.The secondary service life was above 60 h,and the number of repeated activation uses was more than 8 times.??Dehydrogenation of 1,2-cyclohexanediol to produce catechol?1?The core-shell SiO₂@Ni-Rh bimetallic catalyst was prepared by deposition-precipitation method.The catalyst was applied to the dehydrogenation of trans-1,2-cyclohexanediol,and the main products were characterized.Taking the yield of catechol as the index,the process of preparing SiO₂@Ni-Rh catalyst was optimized by single factor experiment.The optimal results were as follows:Ni loading 25%,Rh mass ratio 4%,help The agent was Na₂SO₄ in an amount of 4%by weight.The catalysts were characterized by BET,TG-DSC,SEM and other analytical methods.The catalyst samples were confirmed to have mesoporous structure,high specific surface area and thermal stability,and dehydrogenation of trans-1,2-cyclohexanediol.The reaction for preparing catechol has good activity.After the catalyst was activated online for four times,the reaction was stable for 14h at a higher product yield.After four activations,the catalyst life was over 80 h.?2?The continuous reaction of dehydrogenation of trans-1,2-cyclohexanediol to catechol was carried out by high temperature fixed bed reactor.Under the catalysis of SiO2@Ni-Rh bimetallic catalyst,single factor experiment was used.And the response surface experiment studied and optimized the operating conditions of the continuous dehydrogenation process.The optimal results were:reaction temperature370°C,raw material concentration 10%,liquid hourly space velocity 11 h-1,under optimal operating conditions The conversion of trans-1,2-cyclohexanediol was 99.5%,and the yield of catechol was 93.7%.Compared with the previous literature,under the optimal conditions,the loading of the catalyst is higher,the liquid hourly space velocity reaches 11 h-¹,and the selectivity and yield of the product catechol are higher,94.65%and 93.7%respectively.the comprehensive life of the catalyst is long,and the disadvantage is that the on-line activation step of the catalyst is cumbersome and the operation is complicated.