Improved CO2 Separation Using Aqueous Solutions of 2-Amino-2-hydroxymethyl-1,3-propanediol Promoted with Piperazine

An aqueous mixture of the sterically hindered amine 2-amino-2is a credible CO2 separation solvent. In this work, CO2 absorption kinetics in AHPD/PZ mixtures was investigated in a stirred cell reactor. The solute gas CO2 reacted in parallel with both amines AHPD and PZ. From the absorption rate measurements at 308 K, the second-order rate constant for the reaction between CO2 and PZ was found (k2,PZ = 28 685 m3 (kmol s)-1). Several properties of this blend, such as density, viscosity, and CO2 diffusivity and solubility, were measured. Besides, the dependency of the equilibrium CO2 partial pressure on the loading capacity was studied in a low-pressure vapor-liquid equilibrium setup at 308 K. The highest value of CO2 solubility in this study was 0.83 mol CO2/mol amine, and the corresponding CO2 partial pressure was 130 kPa. The performance of the blend AHPD/PZ (1/0.5 kmol m-3) was tested in a continuous, closed-loop setup comprising an absorber (313 K) and a desorber (383 K). The efficiency of CO2 separation from a CO2/air mixture (12:88 v/v) was 62%, and the regeneration energy constraint was 4.21 MJ (kg CO2)-1. Finally, alumina catalyst was employed for faster CO2 desorption at 368 K in a batch setup. This comprehensive study will promote the application of this candidate AHPD/PZ solvent.

Automated summary

The kinetics of CO2 absorption in AHPD/PZ mixtures were investigated in this study, revealing a second-order rate constant of 28,685 m3(kmol s)-1 for the reaction between CO2 and PZ. Various properties of the blend were measured, including density, viscosity, and CO2 diffusivity and solubility. The efficiency of CO2 separation in a continuous, closed-loop system using the AHPD/PZ blend was found to be 62%.