Role of mono- and diamines as kinetic promoters in mixed aqueous amine solution for CO2 capture

Tertiary amines are thermodynamically efficient CO2 absorbents but unfortunately suffer from low absorption rates. To overcome this issue the use of formulated absorbents incorporating simple aliphatic amines and di-amines as promoters have been suggested. This work describes the fundamental CO2 capture behaviour in tertiary amine diethylethanolamine (DEEA) based solution with a series of kinetic promoters monoethanolamine (MEA), N,N-dimethyl-1,3-propanediamine (N,N-DM13PDA), N,N-dimethyl-1,2-ethanediamine (N,N-DM12EDA), and 4-amino-1-methylpiperidine (4-A1MPD). The CO2 absorption rate and cyclic capacity was significantly enhanced due to the additional diamines. Using NMR technology, the underlying effect of the additives on the chemical speciation e.g. carbamate, (bi)carbonate was interrogated. The absorbents were found to initially favour carbamate at low CO2 loadings, transitioning to the energetically favoured (bi)carbonate adduct as the total CO2 concentration elevates. Unlike the energy intensive MEA absorbent, rapid and deep CO2 removal was achieved in the new proposed di-amine blend solutions, affirming its promising potential for CO2 capture.