Towards Industrially Viable Non-Aqueous Amine Solvent Systems

Ionic liquids represent attractive solvents for CO₂ capture due to their tunable properties and low vapor pressures. We have developed a class of amine solvents for use in non-aqueous conditions that react reversibly with CO₂ to form ionic liquids. We have also looked at several polyamine-containing compounds to increase the number of reactive amine sites for added CO₂ capacity. We are optimizing the solvents for CO₂ capture from coal-fired power plants with a water-saturated flue gas stream. The solubility of water in both the amine precursor and in the ionic liquid formed will influence the system dynamics. The addition of water into the solvent system changes both capacity and viscosity. Under the right conditions, the addition of water can boost capacity by promoting bicarbonate formation. Water can lower viscosity by disrupting packing of the ionic liquid. Since bicarbonate has a relatively low temperature of reversal, the addition of water also affects the temperature at which CO₂ is released from the solvent system. The merit of these advantages will be compared against the parasitic energy penalty for heating water during regeneration. We will additionally present opportunities for further research and optimization of the solvents.