Experimental and simulation study of CO2 and H2S solubility in propylene carbonate, imidazolium-based ionic liquids and their mixtures

Currently, solvent-based absorption is known as an effective technology to capture acid gases, e.g., CO2 or H2S. In this work, the constant-volume method is used to determine CO2 and H2S solubility in propylene carbonate (PC), imidazolium-based ionic liquids (ILs): 1-butyl-3-methylimidazolium tetrafluoroborate [Bmim][BF4], 1-hexyl-3-methylimidazolium tetrafluoroborate [Hmim][BF4], and 1-octyl-3-methylimidazolium tetrafluoroborate [Omim][BF4], and their mixtures at temperature from 303.15 to 333.15 K under pressures up to about 1 MPa. Besides, the quantum chemistry-based COSMO-RS models are used to predict the vapor pressure and the solubility in these solvents. The experimental results illustrate that adding [Omim][BF4] into PC can improve the CO2 and H2S solubility and the H2S/CO2 selectivity compared with the pure PC, which increases with the increasing [Omim][BF4] mass fraction in the mixtures. The simulation with COSMO-RS shows the vapor pressures of PC in the mixtures decreases with the increasing [Omim][BF4] mass fraction. Moreover, the prediction results show that COSMO-RS-Lei model is in much better agreement than COSMO-RS (ADF 2005) for predicting both CO2 and H2S solubility and the prediction accuracy of CO2 is better than that of H2S. Finally, the mixtures of PC and [Omim][BF4] may be used as promising physical solvents to capture CO2 and H2S selectively with high partial pressures because they connect the advantages of organic solvents and ILs. (C) 2019 Elsevier Ltd.