The density, viscosity, and surface tension of aqueous solutions containing three imidazolium bromine ionic liquids (ILs) [C n MIM]Br with different alkyl chain lengths (n = 2, 3, 4) are determined within the temperature ranging from 283.15 to 343.15 K and at ambient pressure, respectively. The effect of the alkyl chain length of the imidazolium cation on the properties of the solutions is investigated. The experimental density and viscosity are satisfactorily described with the linear model and the Vogel–Tammann–Fulcher type equation, respectively. On the basis of the experimental data, the energy barrier and the surface entropy/enthalpy are calculated. The results show that the density and surface tension of aqueous ILs solution decrease and the viscosity increases with the increase of carbon atom number in imidazole ring carbon chain under the same conditions. The surface ordering in each aqueous solution follows [C2MIM]Br > [C3MIM]Br > [C4MIM]­Br. The calculation of the molecular/ionic cluster interaction energy shows that there is a strong interaction between IL and water molecules, and the strong interaction between water and bromine ions is the main factor determining the properties of the solution. The data and results can provide a reliable support for the design and process calculation of chemical absorption cycle with water/IL working pairs.

Experimental measurements for the vapor–liquid equilibria (VLE) of benzene + 1-ethyl-3-methylimidazolium bis­(trifluoromethylsulfonyl)­imide ([EMIM]­[NTf2]), benzene + 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM]­[EtSO4]), and benzene + mixed ionic liquids (ILs) (equimolar [EMIM]­[NTf2] + [EMIM]­[EtSO4] mixture) are performed. The non-random two liquid (NRTL) model binary interaction parameters are then obtained by fitting the new VLE data and the liquid–liquid equilibrium data previously reported. The interactions between chemical species are analyzed using quantum chemical calculations and the COSMO-SAC method, and it is found that the interactions between benzene and ILs are strongly attractive. Taking as a reference the industrial process that uses sulfolane as the entrainer, several novel industrial processes are proposed, which involve either pure ionic liquids [EMIM]­[NTf2] and [EMIM]­[EtSO4] or their mixtures as the extractant for separating aromatic hydrocarbons (benzene) and paraffins (n-hexane). The optimal operating parameters, such as the number of theoretical stages, the extractant-to-hydrocarbon feed ratio, the reflux ratio, and the feed stage, are determined for the different processes. Steady-state process simulations are performed to evaluate the total annual cost (TAC) and the environmental impact (carbon dioxide emissions). It is shown that significant savings in energy consumption (reduction of 19.6–48.7%), TAC (reduction of 6.3–27.1%), and CO2 emissions (reduction of 17.8–47.6%) can be achieved for the processes that use IL extractants, compared to the process based on sulfolane extractant. The proposed IL extractant and the corresponding process are promising alternatives to conventional solvents and processes for aromatic extraction.