Phase Equilibrium Study On Extractive Separation Of Azeotropic System Carbonate And Ethanol Using Imidazolium-based ILs

Organic carbonate is an important industrial chemicals,mainly including dimethyl carbonate(DMC),methyl ethyl carbonate(EMC),diethyl carbonate(DEC),which has a wide range of applications in paint coatings,organic synthesis,medicine,fuel additives etc.As an asymmetric carbonate compound,ethyl methyl carbonate has incomparable advantages compared with other carbonates.it is It is often used as a novel co-solvent in the electrolyte of lithium-ion batteries,which can greatly improve the energy density and discharge capacity of batteries.However,the production process of ethyl methyl carbonate produces a DMC/EMC and ethanol azeotrope,which makes separation of subsequent products difficult to carry out efficiently.Therefore,it is necessary to explore the energy savings and efficient method to seperate azeotrope.To separate the DMC/EMC and ethanol azeotropic mixture,firstly,different ILs of stable nature,low cost,and commonly used for azeotrope separation were screened.The σ-profiles of carbonate,ethanol and ILs were calculated based on the conductor like screening segment activity coefficient(COSMO-SAC)model.The calculated results show that the imidazolium-based ILs with anions[HSO4]-has strong hydrogen bond accepting ability,which confirms the possibility of hydrogen bonding between ILs and ethanol.The interaction energies of ILs with carbonate and ethanol were calculated by molecular simulation and quantum chemistry calculation respectively.The hydrogen bonding between ILs/carbonate and ILs/ethanol were determined by analyzing the calculated results,then the extraction ability of ILs with different anions was evaluated.Finally,the ILs with the anion[HSO4]-are determined the promising extractants for separation of ethanol and EMC mixture due to their abilities to form hydrogen bonds with ethanol.Secondly,the liquid-liquid tie-line data for the ternary systems containing carbonate,ethanol and ILs were measured.The effects of ILs cationic alkyl chain length,ester carbon chain length and temperature on the phase behavior of DMC/EMC+ethanol+ILs were investigated,and the distribution coefficient and selectivity were calculated to evaluate the extraction capacity of the different ILs.Finally,the NRTL model was adopted to correlate the experimental results,and the interaction parameters suitable for the studied system were also optimized,which provided the basis for the extraction separation process design.Moreover,The GUI-MATLAB software for analyzing the mixed Gibbs energy was adopted to check the validation of the correlated parameters.The results show that the model parameters can be verified to ensure the consistency of the correlation parameters obtained.