Solubility of carbon dioxide in aqueous solutions of 2-amino-2-hydroxymethyl-1,3-propanediol

The solubility of CO2 in aqueous solutions of 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD) was measured for AHPD mass fractions w = 0.0015,0.005,0.01   and   0.025 at 283.15, 298.15 and 313.15 K and for CO2 partial pressures within 2–75 kPa. These ranges were compatible with aqueous solutions in use in a CO2 capture process using human carbonic anhydrase metalloenzyme. The influence of carbonic anhydrase on the solubility of CO2 in AHPD solution with w = 0.025 at 283.15, 298.15 and 313.15 K was also studied for CO2 partial pressures below 9 kPa. The modified Kent–Eisenberg model was used to correlate the equilibrium solubility of CO2 in aqueous AHPD solutions and to determine the deprotonation and carbamate stability constants for AHPD solutions. These equilibrium constants were correlated with temperature, amine concentration and CO2 loading. To estimate the physical solubility of CO2 in aqueous AHPD solutions, the solubility of N2O in aqueous AHPD solutions was also measured for AHPD mass fractions w = 0.0015,0.005,0.01,0.025   and   0.10 at 283.15, 298.15 and 313.15 K. It was found that the enzyme did not influence the solubility of CO2 in these solutions as the enzymeʹs function is to catalyze the hydration of CO2 without affecting the CO2 thermodynamic equilibrium.