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A kinetics study of the absorption of CO2 into a mixed aqueous solution of methyldiethanolamine (MDEA) and piperazine (PZ) was investigated by a laboratory disk column within 303−343 K and a weight ratio of MDEA to PZ 50/3−50/10 with a total amine concentration of 3.0 M. A renewal mechanism was proposed, and a kinetic model was established on the basis of the existence of piperazine carbamate. The second-order rate constant of CO2 with PZ was expressed as kp = 4 × 1010 exp(−4059.4/T), which was in good agreement with that of Bishnoi and Rochelle (Chem. Eng. Sci. 2000, 55, 5531). The concentrations of various species in solution were also calculated, and the results indicated that the concentration of free PZ was very low for its special reactivity to form the protonated PZ and carbamate in the MDEA solution when encountering CO2.
Zhang et al. (Fri,) studied this question.