CO absorption into primary and secondary amine aqueous solutions with and without copper ions in a bubble column.

Chemical absorption of CO into aqueous amine solutions using a nonstirred bubble column was experimentally investigated. The performance of CO absorption of four different primary and secondary amines including monoethanolamine (MEA), piperazine (PZ), 2-piperidineethanol (2PE), and homopiperazine (HPZ) were compared. The effects of initial concentration of amine, the inlet mole fraction of CO, and solution temperature on the rate of CO absorption and CO loading (mol CO/mol amine) were studied in the range of 0.02-1 M, 0.10-0.15, and 25-40 °C, respectively. The effect of the presence of copper ions in the amine solution on CO loading was also studied. By comparison of the breakthrough curves of the amines at different operational conditions, it was revealed that the shortest and longest time for the appearance of the breakthrough point was observed for MEA and HPZ solutions, respectively. CO loading of MEA, 2PE, PZ, and HPZ aqueous solutions at 25 °C, 0.2 M of initial concentration of amine, and 0.15 of inlet mole fraction of CO were 1.06, 1.14, 1.13, and 1.18 mol CO/mol amine, respectively. By decreasing the inlet mole fraction of CO from 0.15 to 0.10, CO loading slightly decreased. As the initial concentration of amine and temperature decreased, CO loading increased. Also, the presence of copper ions in the absorbent solution resulted in a decrease in the CO loading of MEA and HPZ aqueous solutions. In case of PZ and 2PE amines, adding copper ions led to precipitation even at low copper ion concentrations.