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Absorption of H2S and CO2 in Aqueous Solutions of Tertiary-Amine Functionalized Protic Ionic Liquids
- Huang, Kuan, Zhang, Jia-Yin, Hu, Xing-Bang, Wu, You-Ting
- Energy & fuels 2017 v.31 no.12 pp. 14060-14069
- absorbents, absorption, acetic acid, aqueous solutions, carbon dioxide, enthalpy, gases, hydrogen sulfide, ionic liquids, natural gas, neutralization, oil and gas industry, solubility, temperature, thermodynamic models, viscosity
- The development of ionic liquid-based absorbents for selective separation of H₂S from CO₂ is of interest to the natural gas industry. In this work, a series of tertiary-amine functionalized protic ionic liquids (TA-PILs) were synthesized by neutralizing one of the tertiary amine groups in diamine compounds with acetic acid, leaving the other tertiary amine group as the functional site for selective absorption of H₂S. To overcome the high viscosity of pure ionic liquids, TA-PILs were dissolved in water to give mixed absorbents. The effects of TA-PIL species, TA-PIL concentration, and experimental temperature on the solubilities of H₂S and CO₂, and absorption kinetics of H₂S and CO₂ in aqueous TA-PILs were investigated systematically. The reaction equilibrium constants and absorption enthalpy of H₂S and CO₂ in aqueous TA-PILs were also calculated by correlating the solubility data with a reaction equilibrium thermodynamic model. Results demonstrated that aqueous TA-PILs have high absorption capacities for H₂S. Although the equilibrium selectivities of H₂S/CO₂ in aqueous TA-PILs are minimized, they still display significant kinetic selectivities for the two gases. More importantly, the TA-PILs designed are featured with low cost and facile synthesis, making them more attractive than other functionalized ionic liquids reported in the literature for application in selective separation of H₂S from CO₂.