Thermodynamic Study of H2S Solubility in Aqueous Solutions of MDEA, MEA, DIPA and DEA

Experimental solubility data for H2S in aqueous solutions of N-methyldiethanolamine (MDEA), diethanolamine (DEA), diisopropanolamine (DIPA) and monothanolamine (MEA) have been measured at various temperatures (40, 55 and 70 oC) and partial pressures of H2S ranging from 20 to 2000 kPa. Solubility data were obtained in a 250 mL autoclave and analyzed by chemical methods. The autoclave was equipped with a pressure transmitter with an accuracy of +/- 0.01 psi and temperature indicator and controller with an accuracy of +/- 1 oC. The compositions of liquid phase were analyzed by gas chromatography using a flame ionization detector (FID). All experiments were carried out in triplicate. Solubility data were correlated by M-KE (modified Kent-Eisenberg) model and equilibrium constant of alaknolamine protonation reaction was expressed by correlation in terms of temperature, H2S partial pressure (or loading) and alkanolamine concentration. In all cases, it was found that the models were able to give a relatively good H2S loading over a wide range of operating conditions.Therefore, the M-KE model may easily predict the solubility of acid gases in alkanolamine aqueous solutions. Average Absolute Deviation (AAD) for modeling of these alkanolamines by M-KE method are 1.75, 1.92, 2.48 and 1.27 for DIPA, DEA, MDEA and MEA aqueous solutions, respectively.