Separation Of Ethyl Methyl Carbonate From The Reaction System

Ethyl methyl carbonate is an environmentally benign asymmetric carbonic ester. It can improve the battery energy density, discharge capacity, safety performance and life span of lithium batteries for its outstanding features such as low viscosity, high dielectric constant, and good solubility of lithium salts. So it is used as excellent organic electrolyte in lithium-ion batteries and will be applied broadly in the future. Now most of the ethyl methyl carbonate used as electrolyte solvent is imported from abroad because of its low purity in the domestic market. Therefore, it is of great social significance to find an effective method of separation of ethyl methyl carbonate and improve its purity.At present, most of the production of ethyl methyl carbonate in industry is by the process of transesterification between dimethyl carbonate and ethanol. The reaction system consists of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and a trace of methanol and ethanol. It is difficult to separate ethyl methyl carbonate from the system. Up to now, there is no report on the separation of the reaction system, and part of the binary vapor-liquid equilibrium (VLE) date for the systems is scarce in the literature. So, the VLE data of the binary systems: ethyl methyl carbonate + methanol, + ethanol, + dimethyl carbonate, and + diethyl carbonate were experimentally determined by a recirculation vapor-liquid equilibrium still at 101.3kPa in this work. The experimental VLE data together with the literature VLE data for the binary systems of methanol + ethanol, methanol + dimethyl carbonate, methanol + diethyl carbonate, ethanol + dimethyl carbonate, ethanol + diethylcarbonate, and dimethyl carbonate + diethyl carbonate were correlated by Wilson, NRTL, and UNIQUAC model. And the model parameters were calculated by non - linear least square method in MATLAB. On basis of this and constant holdup model, the separation of ethyl methyl carbonate by batch distillation was simulated using the software PRO/II. For the slop cut withdrawal period, reservation of heavy key component was chosen as the objective function to study the effects of operating conditions, such as reflux ratio, number of stages, total feed and purity specification of the product on the process under the fixed component composition. For the product withdrawal period, recovery of product was used as objective function to find the optimum reflux ratio. The effects of operating conditions such as number of stages, total feed, and purity specification on recovery of product and total yield were studied. From the simulation results, the optimum process conditions are obtained, which are theoretical plates 50, reflux ratio 23 for slop cut withdrawal period, and 6 for product withdrawal period. To verify the creditability of the simulation results, experiments were carried out under the above optimum process conditions. The results showed that the experimental results agree with the simulation results very well.