Physical and chemical solubility of carbon dioxide in aqueous methyldiethanolamine

Inconsistent trends for the physical solubility of carbon dioxide in aqueou s methyldiethanolamine (MDEA) are presented. These inconsistencies are foun d between data sets for the chemical solubility of carbon dioxide in aqueou s MDEA. In order to rationalize this inconsistency, data are presented for the solubility of nitrous oxide and carbon dioxide in MDEA solutions neutra lized with sulfuric acid. The physical solubility is seen to decrease with increasing ionic strength. Previously published models show the incorrect t rend for the physical solubility of carbon dioxide as a function of loading because of this discrepancy in the data. The electrolyte-NRTL model was su ccessfully used to model the chemical and physical solubility of carbon dio xide in MDEA by defining the reference state for solutes as infinite diluti on in the aqueous phase instead of the mixed solvent. VLE data at high temp erature and high loading are needed for industrially important MDEA concent rations. The N2O analogy needs to be studied further in solutions at high a nd moderate loading as a function of temperature. (C) 2000 Elsevier Science B.V. All rights reserved.