Heat of Absorption of Carbon Dioxide (CO 2 ) in Monoethanolamine (MEA) and 2-(Aminoethyl)ethanolamine (AEEA) Solutions

A method is proposed for measuring the enthalpy of absorption of CO 2 (Δ 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 CO 2 with aqueous solutions of monoethanolamine (MEA) and (2-aminoethyl)ethanolamine (AEEA) over the temperature range of 40−120 °C. By feeding CO 2 in several steps and keeping the change in loading between each new equilibrium rather low (∼0.03−0.07 mol CO 2 /mol amine), it was possible to obtain values of Δ H abs that were semi-differential in loading. Experiments conducted at different temperature levels gave enthalpy values that were differential in temperature. Measured Δ 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 Δ H abs values.