Kinetics of Carbon Dioxide Binding by Promoted Organic Liquids

The reaction kinetics of carbon dioxide and CO₂-binding organic liquids (CO₂BOLs) promoted by piperazine (PZ) and its derivatives were investigated experimentally by stopped-flow conductimetry. The study was carried out at 298K and for a concentration range of 0-0.25kmolm^-3 of PZ, 1-(2-aminoethyl)piperazine (AEPZ) or 1-(2-hydroxyethyl)piperazine (NHEPZ) while the superbase (1,1,3,3-tetramethylguanidine or 1,8-diazabicyclo[5.4.0]undec-7-ene) concentrations were kept constant at 10.0wt%. Based on pseudo-first-order reaction conditions, the intrinsic reaction rate data were analyzed according to a modified termolecular reaction mechanism. The results showed that the rate of reaction between CO₂BOLs and CO₂ could be significantly enhanced by blending with small amounts of PZ, NHEPZ or AEPZ as promoters. To solve the global post-combustion CO₂ problem, novel non-aqueous hybride solvents consisting of CO₂-binding organic liquids and promoters were designed. The blended solvents capture significant amounts of CO₂ due to faster kinetics, with typical half-times of as low as 0.003s in a custom-designed stopped-flow apparatus.