Ionic liquids (ILs) as promising green solvents were first proposed to extract polycyclic aromatic hydrocarbons (PAHs) from fluid catalytic cracking (FCC) diesel. The COSMO-RS model was used for preliminary screening of IL extractants. The liquid-liquid equilibrium (LLE) experiments were performed to show that the IL [BMIM][BF 4 ] has a high selectivity for the model oil system. Further, the LLE experimental results show that the solubility of 1-methylnaphthalene in [BMIM][BF 4 ] is relatively low, while the IL exhibits a high selectivity of n-hexadecane to 1-methylnaphthalene. This means that the use of [BMIM][BF 4 ] can obtain the high-purity products when considering the almost nonvolatility of IL. Compared to the benchmark process, the multistage countercurrent-reflux extraction process can improve the PAHs purity by about 2% at the expense of 5.06% total annual cost and 6.42% energy consumption, rendering the use of IL to extract PAHs from FCC diesel more feasible in industry.

Ionic liquids (ILs) as green solvents were first used to capture 1,2-dimethoxyethane (DMET) from exhaust gas. The vapor liquid equilibrium (VLE) data of [EMIM]­[TF2N] + DMET and triethylene glycol (TEG) + DMET were measured. The results showed that the popular UNIFAC-Lei model is in good agreement with experimental data. The gas absorption experiment with [EMIM]­[TF2N] as absorbent was conducted. It demonstrates that the IL has good separation performance for capturing DMET, the absorption ratio being 87.32%. Then, the absorption capacities of 45 ILs for DMET were calculated by COSMO-RS model, while DMET removal mechanism was explored by σ-profiles analysis and molecular dynamics (MD) simulation. Finally, industrial scale process simulation using [EMIM]­[TF2N] and TEG as absorbents to capture DMET was made. Compared to the benchmark TEG process, the total operating cost and the total annual cost (TAC) in the IL process decrease by 24.06% and 17.15%, respectively. This further proves that ILs have great application potential for the condensable volatile organic compounds (VOCs) capture, especially in energy saving and improving economic benefits.

In this work, a mixed absorbent of an ionic liquid (IL) and triethylene glycol (TEG) is first proposed for natural gas (NG) dehydration. The hydrophilic [EMIM]­[BF4] is selected as an appropriate IL composition from 240 potential candidates by calculating the thermodynamic separation factors (i.e., solubility and selectivity). The separation mechanism of NG dehydration with the mixed absorbent of [EMIM]­[BF4] + TEG at the microscopic molecular level is systematically unraveled by employing the COSMO-RS model and quantum chemical calculations. The solubility of CH4 in pure [EMIM]­[BF4] and TEG, as well as in binary mixtures of [EMIM]­[BF4] + H2O and [EMIM]­[BF4] + TEG, is experimentally measured and predicted by the modified (mod.) UNIFAC-Lei model. It is proved that the mod. UNIFAC-Lei model can well predict the gas–liquid equilibrium (GLE) and be successfully extended from binary to ternary systems. In the dehydration experiment, the mixed absorbent shows an excellent dehydration performance (i.e., the water content of the product gas is decreased to 172 ppm, in mole fraction). The equilibrium (EQ) stage model embedded with the mod. UNIFAC-Lei model parameters is built to carry out the process simulation of CH4 dehydration at the laboratory and industrial scales. The results show that the total annual cost (TAC) of the optimized process with mixed solvents is reduced by 33.63 and 15.98%, respectively, at the same separation conditions when compared to that of pure TEG and pure IL processes. This confirms that the IL-based mixed absorbent is a promising alternative to pure ILs or conventional solvents for applications in the field of gas separation and purification.

Deep eutectic solvents (DESs) as promising green solvents have been proposed for the removal of SO 2 from fuel gases. In this work, an efficient SO 2 absorption strategy based on three 1-ethyl-3-methylimidazolium chlorine ([EMIM][Cl])-based DESs, that is, [EMIM][Cl]−ethylene glycol, [EMIM][Cl]− triethylene glycol, and [EMIM][Cl]−acetamide DESs, was investigated. A comparison of the predicted absorption efficiency via molecular dynamics (MD) and that obtained from experimental results is used to validate the simulated results.Then, the interaction energy and radial and spatial distribution functions are calculated based on the MD simulation results to provide molecular insights into the separation mechanism. The hydrogen bonding and van der Waals interactions between molecules and SO 2 were investigated by quantum chemical calculations. The results demonstrate that the anion ([Cl] − ) plays a significant role in the absorption process. As a further step, a modeling method for SO 2 absorption and DES recovery based on Aspen Plus is established. Under optimal operating conditions, the SO 2 absorption ratio exceeds 99.6%, and the DES recovery ratio is 99.9%. DESs, as a new type of absorbent, will provide new insights for the sustainable development of the green chemical industry.

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