Kinetics of the Absorption of Carbon Dioxide into Mixed Aqueous Solutions of Piperazine and Triethanolamine

Abstract

The reaction kinetics of the absorption of CO₂ into mixed aqueous solutions of piperazine (PZ) and triethanolamine (TEA) are investigated using the wetted wall column at temperatures of 303.2 to 313.2 K. The physical properties such as density and viscosity of the aqueous alkanolamine solutions, and the solubility and diffusivity of the nitrous oxide in aqueous alkanolamine solutions are also measured. The N₂O analogy is applied to estimate the solubilities and diffusivities of CO₂ in aqueous amine systems. Based on the pseudo-first-order for CO₂ absorption, the overall pseudo first-order reaction rate constants were determined from the kinetics measurements. For CO₂ absorption into mixed aqueous solutions of PZ and TEA, it is found that the addition of small amounts of PZ to aqueous TEA solutions has a significant effect on the enhancement of the CO₂ absorption rate. For the CO₂ absorption rate model, a second-order reaction rate model is applied for both reactions of CO₂ with PZ and TEA. The overall absolute percentage deviation for the calculation of the apparent rate constant k_app was 4.6% for the kinetics data measured. The model is satisfactory in representing the CO₂ absorption into mixed aqueous solutions of PZ and TEA.