Diamino protic ionic liquids for CO2 capture
A series of multifunctional protic ionic liquids (PILs), some of which are based on a combination of primary and tertiary amines in the same moiety coupled with a carboxylic acid, have been synthesised and employed for CO2 capture, yielding absorption capacities comparable to standard absorbents. In contrast to traditional amine absorbers, CO2 was found to desorb at lower temperatures and hence could result in a significant reduction in both the energy required to strip the absorber of CO2 and the thermally activated degradation mechanisms, which in traditional absorbers result in the loss of absorber and the production of toxic compounds. The lower basicity of the amine sites resultant from PIL formation decreases the binding energy of the CO2 to the absorber. The weaker basicity is also evidenced by lower pH of the PIL CO2 absorbers, which reduces common corrosion problems associated with traditional amine absorbers.