Efficient Absorption of 1,2-dichloroethane by Ionic Liquids

The traditional organic solvent absorption process is characterized by high energy consumption and large solvent volatility lass. To solve this problem, this work proposes to use ionic liquids (ILs) for efficient absorption of 1,2-dichloroethane from waste gas, and under the guidance of predictive molecular thermodynamic model this paper systematically investigated the practical application prospects from the molecular to system scales. The COSMO-RS model was used to screen 476 kinds of ILs. The effect of IL structure on the absorption of 1,2-dichloroethane was investigated from the cationic skeleton, the length of carboxylate anion carbon chain and the degree of fluorination. It was found that the nonaromatic non cyclic cations and the shorter carboxylate anion carbon chain length and the nonfluorinated anion structure were conducive to the better absorption of 1,2-dichloroethane by ILs, Finally, 1-butyl-3-methylimidazole acetate (BMIM Ac) was determined as the appropriate absorbent. The optimization experiment of absorption conditions was conducted at different temperatures and partial pressures, and the results showed that the saturated absorption capacity ofBMIM Ac for 1,2-dichloroethane reached 2177 mg/g at 20℃ and atmospheric pressure. Through quantum chemistry calculation and wave function analysis, the microscopic mechanism of ionic liquid absorbing 1,2-dichloroethane was discussed. The reason for enhanced absorption is due to the strong HB effect and vdW dispersion effect, which are greatly contributed by anions. Cations are mainly combined with C-H … Cl interaction and vdW dispersion effect. Conceptual design and process simulation were conducted on the process of DCE absorption by ILs. An equilibrium stage model (EQ) was established for the absorption process, and COSMO-SAC was selected as the thermodynamic model. For the selected operating conditions, the removal rate of 1,2- dichloroethane by ILs reached 99. 88%. Comparing ILs with traditional organic solvents, it was found that ILs have lower product gas loss and energy consumption. This indicates that using ILs to absorb 1,2- dichloroethane is a good strategy and has certain industrial potential.