Kinetics of absorption of carbon dioxide into aqueous solutions of 2-amino-2-hydroxymethyl-1,3-propanediol

In this work the kinetics of the reaction between CO2 and a sterically hindered alkanolamine, 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD) were determined at temperatures of 303.15, 313.15 and 323.15 K in a wetted wall column contactor. The AHPD concentration in the aqueous solutions was varied in the range 0.5–2.4 kmol m−3. The ratio of the diffusivity and Henry's law constant for CO2 in solutions was estimated by applying the N2O analogy and the Higbie penetration theory, using the physical absorption data of CO2 and N2O in water and of N2O in amine solutions. Based on the pseudo-first-order for the absorption of CO2, the overall pseudo-first-order rate constants were determined from the kinetics measurements. By considering the zwitterion mechanism for the reaction of CO2 with AHPD, the zwitterion deprotonation and second-order rate constants were calculated. The second-order rate constant, k2, was found to be 285, 524, and 1067 m3 kmol−1 s−1 at 303.15, 313.15, and 323.15 K, respectively.