Kinetics of Carbon Dioxide Absorption by Nonaqueous Solutions of Promoted Sterically Hindered Amines

The mechanism and kinetics of CO2 capture using piperazine (PZ) promoted nonaqueous solutions of 2-amino-2-methyl-1,3-propanediol (AMPD) and 2-amino-2-ethyl-1,3-propanediol (AEPD) were investigated by stopped-flow technique. The termolecular mechanism was used to model the kinetics of the reactions. AMPD or AEPD like other sterically hindered amines absorbs CO2 in an equimolar ratio that is significantly higher than that of monoethanolamine (MEA). However, the steric hinderance results in decreased reaction rate as in the case of AMPD and AEPD. The reaction can be promoted by addition of small amounts of cyclic polyamines, such as PZ or its derivatives. Our results show clearly that nonaqueous solutions of AMPD and AEPD can achieve reaction rates comparable to commercial systems by the addition of small amounts of PZ.