Study On Catalytic Hydrogenation Of Mixed Dibasic Acid Dimethyl Ester And Separation Of Products Distillation

In the production of adipic acid production,dicarboxylic acid and glutaric acid-based dibasic acid by-products are also produced.Mixed dibasic acids containing succinic acid and glutaric acid with a small amount of adipic acid are known for nylon acid.Nylon acid is converted into a mixed dibasic ester?DBE?by esterification,and the main component is dimethyl succinate,dimethyl glutarate,and dimethyl adipate.The 1,4-butanediol?1,5-pentanediol and 1,6-hexanedio,which are catalytically hydrogenated products of dibasic esters,have extremely high added value and are widely used in polyurethanes,plasticizers,and pharmaceuticals.In this paper,a laboratory-made Cu-Zn-Al catalyst was used to prepare mixed glycols.At the same time,catalytic hydrogenation products were simulated and separated using Aspen Plus.Using dimethyl adipate and hydrogen as raw materials,a laboratory-made copper-based catalyst was used to perform the reaction using a fixed bed reactor.Through single-factor and orthogonal experiments,the effects of reaction temperature,reaction pressure,liquid hourly space velocity,and hydrogen ester molar ratio on the catalytic hydrogenation of dimethyl adipate were investigated.The suitable process conditions were obtained:reaction temperature 230?,reaction pressure 7 MPa,liquid hourly space velocity 0.45h^-1,and hydrogen ester molar ratio130.Under these conditions,the conversion of dimethyl adipate was 99.13%and the yield of 1,6-hexanediol was 98.37%.In a fixed bed reactor,the same catalyst as described above was used to react the mixed dibasic acid dimethyl ester?dimethyl succinate 20.37%,dimethyl glutarate63.31%,dimethyl adipate 16.32%?and hydrogen as raw materials.Through single-factor and orthogonal experiments,the effects of reaction temperature,reaction pressure,liquid hourly space velocity,and hydrogen ester molar ratio on the catalytic hydrogenation of mixed dibasic esters were investigated.The appropriate process conditions were determined:reaction temperature 240?,reaction pressure 6MPa,liquid hourly space velocity 0.45h^-1,and hydrogen ester molar ratio 170.The conversion of dimethyl succinate was 98.67%,the yield of 1,4-butanediol was48.51%,the conversion of dimethyl glutarate was 98.22%,and the yield of1,5-pentanediol was 90.62%.The conversion of dimethyl acid was 97.95%and the yield of 1,6-hexanediol was 89.76%.Catalytic hydrogenation products of mixed dibasic acid dimethyl ester was analysised by Gas Chromatography.The mass fractions of each component were that methanolwas28.13%,tetrahydrofuranwas0.85%,dimethylsuccinatewas0.2%,dimethyl glutarate was 1.19%,dimethyl adipate was 0.3%,1,4-butanediol was6.47%,1,5-pentanediol was 39.46%,1,6-hexanediol was 12%,and impurities was12.4%.In order to obtain the main product of the mixed glycol,the Aspen Plus was used to simulate the separation of the hydrogenation product to obtain the corresponding process and separation parameters.Distillation tower B1:reflux ratio of0.42,the number of plates is 7;distillation tower B2:reflux ratio of 12.2,the number of plates is 38;distillation tower B3:reflux ratio of 3.28,the number of plates is35.The mass fractions of 1,4-butanediol,1,5-pentanediol,and 1,6-hexanediol in the obtained product were 80.9%,99%,and 95.7%,respectively.Distillation experiments were performed according to the separation parameters simulated.The mass fractions of 1,4-butanediol and 1,5-pentanediol at the top of the tower were 76.34%and 98.7%,respectively.The mass fraction of the 1,6-hexanediol in the tower reactor was 94.2%.