Quantitative analysis of the liquid phase by FT-IR spectroscopy in the system CO2/diethanolamine (DEA)/H2O

► Speciation data and PCO2 were measured for the system DEA/H2O/CO2. The apparent Henry constants of CO2 were obtained from these results. The CO2 Henry constant decreases with temperature, is independent of the CO2 loading. FT-IR spectroscopy was used to measure the liquid phase speciation in water–diethanolamine (DEA)–CO2 system, the CO2 loading varying from 0.04 to 0.9. The DEA mass fractions in the unloaded solution were 0.2, 0.3 and 0.4, and the temperature varied from 298.1K to 333.1K. The concentrations of carbamate and molecular CO2 have been experimentally determined and the other species concentrations (DEA, protonated DEA, bicarbonate) have been deduced from mass balances and electroneutrality relation. These values, combined with the measurement of CO2 partial pressure in equilibrium with the liquid phase, allow the determination of apparent CO2 Henry constant (HCO2)DEAsolution original values. These results show that (HCO2)DEAsolution is independent of the CO2 loading. Moreover, it is shown that the increase of temperature results in a decrease of (HCO2)DEAsolution.