2-Amino-2-hydroxymethyl-1,3-propanediol for CO₂ capture: study on equilibrium, absorption kinetics, catalytic desorption, and amine regeneration

The CO2-capturing performance of a sterically hindered amine, 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD), was systematically studied in this work. First, absorption kinetics was investigated using the stirred-cell technique. At T = 308 K, CO2 reacted with AHPD according to a second-order reaction (rate constant = 264 m(3)/kmol-s), whose activation energy was 33 kJ/mol. Second, the solubility of CO2 in AHPD at 308 K was measured up to 100 kPa CO2 partial pressure. For instance, it was shown that the loading capacity of AHPD (2.5 M) was 0.56 mol/mol, while the equilibrium CO2 partial pressure was 79 kPa. Third, a closed-loop absorber-desorber setup was used to test solvent performance for capturing CO2 from CO2/air mixture (12:88 v/v). The two columns were continuously operated at 313 (absorber) and 383 K (desorber) at 0.1 MPa pressure. Around 75% CO2 was absorbed using 12 wt. % AHPD (or 0.9 M). The value of Q(Reg) (regeneration energy) was 6.28 MJ/kg CO2. It was thus evident that AHPD is a credible hindered amine-based solvent. A comparison of its equilibrium, kinetic and regeneration features with 2-amino-2-methyl-1-propanol (AMP) was provided. Finally, three rate promoters-hexamethylene diamine (HMDA), monoethanolamine (MEA) and AMP-were added to AHPD. The performance of HMDA was most promising. In a batch desorption setup, it was shown that alumina catalyst improved desorption of CO2 from loaded AHPD/HMDA mixtures. This work will stimulate further interest in the use of AHPD solutions for CO2 removal.