Study On The Preparation Of Acetic Ester By Reactive Distillation Coupled With Separation

Acetic ester is widely used in the fields of pharmaceuticals,perfume,pesticide industry,cleaning agent and biodiesel due to its low toxicity,strong solubility and good biodegradability.To address the difficult separation of the azeotrope and high energy consumption in the reaction distillation synthesis of isopropyl acetate(IPAC)and nbutyl acetate(n Bu OAC),molecular simulation,multi-objective optimization is employed to investigate the optimization process of coupling high-performance separation solvents with reaction separation,as well as the comprehensive evaluation of the economic and environmental benefits of the process.In view of the problems of azeotropic phenomenon of products,low purity and high energy consumption of IPAC production using traditional reactive distillation(RD)synthesis process,this study proposed an enhanced processes of reactive extraction distillation(RED),reactive extraction dividing-wall column distillation(REDWC)and pervaporation coupling reactive extraction distillation(REDPV).Firstly,a polar analysis is performed using a COSMO-fragment activity coefficient model to calculate the surface charge density distribution of 10 organic solvents,including dimethyl sulfoxide(DMSO)and ethylene glycol,with the IPAC-water system.Based on the analysis,DMSO is determined to be the preferred extractant.Secondly,the RED process of coupling reaction,and extractive distillation in a single column and the REDWC process with dividing-wall column were developed based on the reaction kinetics.Considering the high energy consumption of the solvent recovery process,the pervaporation unit is used to replace the solvent recovery column to develop the REDPV process.Multiobjective genetic algorithm is employed to perform nonlinear optimization of the development process,with the total annual cost(TAC)and environmental emissions as the objective functions.The results showed that compared with the traditional RD process,the TAC and environmental emissions of the RED process were reduced by42.69% and 49.82%,respectively,and the REDWC process are reduced by 45.06% and52.93%.Compared with the RED process,the TAC and environmental emissions of the REDPV process were further reduced by 14.45% and 34.55%.For the complexity of the ternary azeotrope separation of IPAC/isopropanol(IPOH)/water in the IPAC synthesis process,the selectivity between 169 ILs ionic liquids(ILs)and the system is calculated.Based on the non-bond interaction energy,radial distribution function and spatial distribution function,the effects of six imidazolebased ILs structures on the separation performance are investigated,and 1-ethyl-3-methylimidazolium acetate([EMIM][AC])is determined as the preferred extractant.The vapor–liquid equilibrium of the system under the influence of [EMIM][AC] is measured to verify the model used for the calculation.A new mixed solvent extractive distillation(MSED)separation process using [EMIM][AC] + DMSO as solvent is developed.The optimal mixing ratio and process parameters are determined by multiobjective optimization.The heat pump assisted thermal integrated mixed solvent extraction distillation(HPHIED)process is developed to realize heat recovery and consumption reduction based on the analysis of heat exchange network.The results showed that the TAC and environmental emissions of MSED process are 26.83% and25.32% lower than that of single solvent extractive distillation process,and the TAC and environmental emissions of HPHIED process were 11.02% and 35.83% lower than that of MSED process.To address the issue of overcapacity caused by the byproduct methyl acetate(MEOAC)in the production process of polyvinyl alcohol,this study synthesized n-butyl acetate(n Bu OAC)via ester exchange reaction between MEOAC and butyl alcohol,realizing the recycling of MEOAC and the clean production of n Bu OAC.Based on the reaction kinetics,reactive distillation coupled extractive distillation(RDED),reactive distillation coupled side-line extractive distillation(SLRED)and pervaporation coupled reactive distillation(RDPV)transesterification processes are developed.The multiobjective optimization results showed that the RDPV process had the best economic and environmental performances,with a total annual cost(TAC)8.17% and 6.46% lower than the RDED and SLRED processes,respectively.Regarding environmental emissions,the RDPV process is associated with 23.13% and 3.51% lower emissions than the RDED and SLRED processes,respectively.In this work,molecular simulation is used to screen the optimal extractants and developed a process design and process intensification for the reaction separation coupling of the synthesis of acetic acid esters.A series of energy-saving processes are developed to improve the energy utilization efficiency of the distillation process,which has important guiding significance for the energy-saving and consumption-reducing separation of azeotropes and the clean production of acetic acid esters in practical industrial applications.