Research On Reactive Dividing Wall Column Process Of Dimethyl Adipate

Dimethyl adipate is not only an organic chemical material,but also an important fine chemical product.It is widely used in the production of plasticizers,high-grade coatings,synthetic resins and detergents,especially the main raw materials for industrial hydrogenation of 1,6-hexanediol,with huge market demand.However,the production capacity of dimethyl adipate is relatively low,which is far from meeting the market demand.As a result,the market price of dimethyl adipate remains high.At the present,problems such as low production capacity,high investment cost,serious environmental pollution,long and complex process route and so on hinder the improvement of DMA production capacity.The purpose of this paper is to explore the shortcomings of the traditional process,improve the coupling degree of reaction and separation process,and develop a high efficiency and energy saving separator reaction distillation process.The main contents of this study can be summarized as follows:1)DMA synthesis reaction of methanol and adipic acid was studied,including catalyst selection,reaction thermodynamics,reaction kinetics and determination of the optimal reaction conditions.Firstly,the resin catalysts that catalyzed the reaction were screened,and the activity,stability and selectivity of cation exchange resin were investigated,and the NKC-9 macroporous cation exchange resin catalyst was screened.Then,under the condition of NKC-9 catalyst,the reaction thermodynamics was studied and the equilibrium constant was obtained.Secondly,the dynamic equation of the reaction of methanol and adipic acid catalyzed by NKC-9 catalyst was obtained by kinetic experiment.Finally,the optimal reaction conditions were determined as alkyd ratio 7.5,reaction temperature 73℃,catalyst dosage 17% of acid mass,which provided basic data for process simulation.2)Research on the traditional three-tower process.Firstly,by exploring and studying the properties of various substances in the system(reaction mixture),appropriate physical properties were selected,and the binary interaction parameters of the NRTL equation of the system were obtained by fitting the experimental data and estimating the physical properties.Secondly,the concept of process flow is analyzed by phase diagram,and the construction process of three-tower process is discussed.Then,the steady state simulation of the process was carried out,and the process parameters such as plate number,reflux ratio and feed position were obtained,and the influence of reflux ratio,operating pressure and other operating conditions on the reaction distillation column was explored.In the end,it was found that there were two deficiencies in the process: the large amount of methanol required and the limited quality of DMA products.3)Conduct a small test of reactive distillation.It is proved that the reactant hexanedioic acid can achieve the conversion rate of nearly 100% in the process of reactive distillation.In addition,the effects of reflux ratio and feed volume on the reaction distillation column were investigated.There is an upper limit of the feed amount of adipic acid,when the upper limit is exceeded,the reaction distillation column will not be able to achieve the complete conversion of adipic acid.4)The high efficiency Reactive Dividing wall column process was proposed.First by rezoning tower process of each tower in the separation of tasks,and through the phase diagram analysis determine the rationality of planning,got a twin towers process,and the process simulation calculation,the results show that the towers process the three towers energy-saving effect is improved obviously,which provides efficient clapboard reaction distillation is put forward with theoretical foundation;Then,the equipment integration of the two-tower process resulted in a more energy-saving and efficient barrier Reactive Dividing wall column process(RDWC).The simulation results showed that the RDWC process could save 60.401% less energy than the three-tower process,which had a huge energy saving potential,and at the same time avoided the serious excess of methanol and poor quality of DMA in the three-tower process.