Low temperature, pre-combustion carbon dioxide (CO₂) capture is typically accomplished using physical solvents such as Solexol™. This is due to the high partial pressure of CO₂ in the flue gas stream which is sufficient to dissolve significant amounts of CO₂ into the solvent without the need for additional chemical reactions. Regeneration of the solvent and release of CO₂ can be accomplished with increased temperature and/or pressure reduction. However, there is a need to create solvents that are tolerant to sulfur, and water, which can operate at higher temperatures. In addition, the solvents need to have low viscosity, high CO₂ solubility, and excellent CO₂/hydrogen (H₂) selectivity.

This invention describes the use of allyl group containing ionic liquid solvents (ILs) for pre-combustion CO₂ capture. The inclusion of allyl groups into ionic liquids structure produces ILs with lower viscosity and better CO₂ solubility than their alkyl counterpart. In addition, these materials tend to be tolerant to sulfur and water. The ionic nature of these materials renders them with low vapor pressure, high thermal stability and high CO₂/H₂ selectivity.