Heat of absorption of carbon dioxide (CO2) in monoethanolamine (MEA) and 2-(Aminoethyl)ethanolamine (AEEA) solutions

A method is proposed for measuring the enthalpy of absorption of CO2 (Delta H-abs) that is differential in temperature and semi-differential in loading. A 2-L reaction calorimeter was used to measure the enthalpy of absorption of CO2 with aqueous solutions of monoethanolamine (MEA) and (2-aminoethyl)ethanolamine (AEEA) over the temperature range of 40-120 degrees C. By feeding CO2 in several steps and keeping the change in loading between each new equilibrium rather low (similar to 0.03-0.07 mol CO2/mol amine), it was possible to obtain values of Delta H-abs that were semi-differential in loading. Experiments conducted at different temperature levels gave enthalpy values that were differential in temperature. Measured Delta H-abs values were compared with integral values found in the literature and with differential values calculated from solubility measurements. The experimental results indicate that the use of the Gibbs-Helmholtz equation in an aggregate form does not necessarily give an accurate description of the Delta H-abs values.