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., CO 2 or H 2 S. In this work, the constant-volume method is used to determine CO 2 and H 2 S solubility in propylene carbonate (PC), imidazolium-based ionic liquids (ILs): 1-butyl-3-methylimidazolium tetrafluoroborate [Bmim][BF 4 ], 1-hexyl-3-methylimidazolium tetrafluoroborate [Hmim][BF 4 ], and 1-octyl-3-methylimidazolium tetrafluoroborate [Omim][BF 4 ], 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][BF 4 ] into PC can improve the CO 2 and H 2 S solubility and the H 2 S/CO 2 selectivity compared with the pure PC, which increases with the increasing [Omim][BF 4 ] mass fraction in the mixtures. The simulation with COSMO-RS shows the vapor pressures of PC in the mixtures decreases with the increasing [Omim][BF 4 ] 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 CO 2 and H 2 S solubility and the prediction accuracy of CO 2 is better than that of H 2 S. Finally, the mixtures of PC and [Omim][BF 4 ] may be used as promising physical solvents to capture CO 2 and H 2 S selectively with high partial pressures because they connect the advantages of organic solvents and ILs.