CO2 Solubility in Hybrid Solvents Containing 1-Butyl-3-methylimidazolium Tetrafluoroborate and Mixtures of Alkanolamines

To reduce the rate of climate change, feasible and energy-efficient solutions need to be found to capture CO 2 at low pressure from flue gas emitted by various industries and energy sectors worldwide. The use of solvents to selectively absorb CO 2 is a promising option for CO 2 capture. This research investigated the solubility of CO 2 in hybrid solvents containing the 1-butyl-3-methyl imidazolium tetrafluoroborate [bmim][BF 4 ] ionic liquid with mixtures of up to three alkanolamine solvents, namely monoethanolamine (MEA), diethanolamine (DEA), and methyl-diethanolamine (MDEA). Gravimetric analysis was used to measure equilibrium CO 2 solubility in the hybrid solvents containing various compositions of the above components at CO 2 partial pressures of 0.05 MPa to 1.5 MPa and temperatures of 303.15 K to 323.15 K. CO 2 solubility in these solvents was benchmarked against pure ionic liquids, as well as conventional alkanolamine solvents, and modeled using the Posey–Tapperson–Rochelle model for the alkanolamines present and the SRK equation of state for the ionic liquid present in the hybrid solvents. It was found that the hybrid solvents achieved significantly higher CO 2 solubility at low pressure than pure ionic liquids and conventional alkanolamine solvents. Modeling, however, was found to be less accurate for hybrid systems than data modeled for pure ionic liquid systems.