Enthalpies of absorption of carbon dioxide in aqueous diethanolamine solutions

Abstract

An isothermal flow calorimeter was used to measure the enthalpies of absorption of carbon dioxide in aqueous 20, 35, and 50 wt.% diethanolamine (DEA) solutions. The experimental temperature and pressure ranges were 299.82–399.82 K and 0.087–1.121 MPa, respectively. The experimental equipment and procedure are described, with emphasis on the complexities originating from the difficulty of measuring the enthalpy of absorption of a gas in an aqueous solution. The calorimetric data were also found to be useful in determining the equilibrium concentrations of CO 2 in the DEA solutions. Both enthalpy of absorption and equilibrium concentration data for CO 2-aqueous DEA systems are reported and compared with existing values from other investigations. The enthalpy of absorption of CO 2 in aqueous DEA solutions was found to be independent of pressure and DEA concentration, and linearly dependent upon the temperature. An equation is given for predicting the enthalpy of absorption over the ranges of temperatures, pressures, and concentrations investigated.