Study On Synthesis Process Of Diethyl 2-Ethyl-2-Phenylmalonate Via Reactive Distillation

Diethyl 2-ethyl-2-phenylmalonate is an organic intermediate used in the production of central nervous drugs,which can be used in the production of phenobarbital,primidone and other neurological drugs.The existing synthesis process uses 20%sodium alcohol as catalyst,ethyl phenyl acetate,diethyl carbonate and bromoethane as raw materials,through the claisen condensation and ethylation reaction to synthesize the product.The reaction efficiency is restricted by batch operation and long production cycle.Therefore,it is of great significance to develop an efficient synthesis process of diethyl 2-ethyl-2-phenylmalonate to further improve the production capacity of products.In this work,reactive distillation technology was used to improve the claisen condensation reaction.The effects of the reaction time of claisen condensation reaction,the ratio of raw materials and the reaction time of ethylation on the yield of the product were determined by experiments.The optimized reaction time of condensation reaction is 2 h,the ratio of ethyl phenylacetate to diethyl carbonate is 1:4,the ethylation reaction time is 3 h.Based on the COSMO-SAC model,the infinite activity dilution coefficient of each component in the reaction system was calculated and the data were regression to obtain the interaction parameters.The process with an annual output of 1400 t product was simulated,and the process parameters were optimized based on sequential iterative optimization sequence.The feasibility of the process was evaluated by energy,economy,environment and exergy analyses.The results show that the operation cost of the process is 1.597×10⁷$/y,and the capital cost is 4.596×10⁵$/y.When the market price of the product is not less than 2.1×10⁴$/t,the process has the potential of industrial application.The global warming potential（GWP）and acid potential（AP）caused by high energy consumption of reactive distillation unit accounted for 58.9%and 50.28%of the total process emissions,respectively.Exergy loss of separation and purification unit was relatively high,accounting for about 48.1%of the whole production process.A double-column pressure-swing batch distillation and a multivessel double-column pressure-swing batch distillation process were designed to separate the recovered bromoethane-ethanol azeotrope and the ternary mixture with one azeotrope of diethyl carbonate-bromoethane-ethanol.Based on the non-dominated sorting genetic algorithm II（NSGA-Ⅱ）,multi-objective optimization of process parameters was carried out with the equipment cost and carbon dioxide emissions of the two separation processes as objective functions,and the operating pressure of the high-pressure column as decision variables.According to the multi-objective optimization of the double-column pressure-swing batch distillation process for separating bromoethane-ethanol,the operating pressure of the high-pressure column is 7 atm.Under this pressure,the capital cost of the process is 2.142×10⁵$/y,the CO₂ emission is 1.146×10⁶ kg/h,and TAC is 1.942×10⁵$/y.The operation pressure of the high-pressure column determined by the multi-objective optimization of the multivessel double-column process is also 7atm.Under this pressure,the capital cost of the process is 2.635×10⁵$/y,the CO₂emission is 3.990×10⁵ kg/h,and the TAC is 1.294×10⁵$/y.