Process Modeling And Optimization For Oxidation Of Cyclohexanone To Adipic Acid Using Oxygen As Oxidant

Adipic acid is one of the main feedstock for the manufacture of Nylon66, polyesters,resins andthe like. It is conventially produced by the two-step oxidation of cyclohexane using nitric acid as anoxidant. This mthod has many disadvantages due to its complicated process and envioronmentalpollution. Our group has developed a new process oxidating cyclohexanone to adipic aicd, usingoxygen as an oxidant, acetic acid as solvent and a special substant as catalyst. This process usingenvironmentally friend oxidant instead of nitric acid, not only saves the cost of raw material, wastedisposal costs, power costs, but also decreases the corrosion of equiupment.The oxidation of cyclohexanone to adipic acid is a gas-liquid-solid three-phase reation process.During the oxidation process, acetic acid is the solvent and oxygen is oxidant. Adipic acid it the mainproduct, and byproducts such as glutaric acid, succinic acid, water are formed. The designed processincludes oxidation reaction system, crystallization separation system, product purification andreaction mixtures distillation system. The basic thermodynamic data of this reaction system isextremely esstential for the design, simulation and optimization of the related system.This thesis will focus on the modeling of the abovementioned units and studying of thechemical engineering problem. Based on these work, the whole process simulation, analysis andoptimization will be conducted.The thesis centers on the following parts.Pase Equilibrium ResearchFirst, the liquid-liquid equilibrium for the system was studied. The experimental apparatus andthe correspondent analysis method were built. The LLE data for three ternary systems (water+cyclohexane+acetic acid, water+cyclohexane+cyclohexanone, and water+acetic acid+cyclohexanone) were determined at atomospheric pressure. The experimental data was correlatedusing NRTL and UNIQUAC models and the binary interaction parameters were obtained.Second, the solid-liquid phase equilibrium for the system was studied. The experiemtalapparatus and the correspondent analysis were built. The solubilities of adipic acid, glutaric acid,succinic acid in binary acetic acid+water and acetic acid+cyclohexane solvent mixtures weremeasured at atmospheric pressure and (303.2~343.2) K. The literature data for the solubilities of thethree dicarboxylic acids in pure cyclohexanone, acetic acid and water were ascertained throughexperiemtns before citing these literature data. The experimental data was correlated with the NRTLmodel and the binary interaction parameters were obtained.The Whole Process Simulation and Analysis.The designed process includes oxidation reaction system, crystallization separation system, product purification and reaction mixtures distillation system. Based on the process design and thebasic data research, the whole process simulation was conducted using ASPEN PLUS software. Usersubroutines were established applying Visual Fortran software. The user-defined module wasdeveloped in the ASPEN PLUS. The simulation results were analysed in detail. Two designs ofreaction mixtures distillation system were compared and the better scheme was ascertained.Optimization of the ProcessThe SENSITIVITY tool in ASPEN PLUS software was applied to optimize operatingparameters. The residence time and the amount of oxygen of the reaction were optimized. Refluxration, feed stage and the distillation of three refining column in reaction mixuters distillation systemwere optimized using sensitivity analysis. The optimal process parameters could be found throughthe simulation and optimization of operating parameters. The result showed that the energyassumption could be reduced and the process was simplified. Pinch techonology was used for thesystem energy optimization. With the help of ASPEN ENERGY ANALYZER software, the energyoptimization was conducted. The result showed that the energy was greatly reduced after theoptimization.