Solubility of CO2+ H2S gas mixture into aqueous N-methyldiethanolamine solution blended with 1-butyl-3-methylimidazolium acetate ionic liquid

The solubility of a acid gas mixture (70 mol% CO2 + 30 mol% H2S) into aqueous solution of Nmethyldiethanolamine (MDEA) blended with 1-butyl-3-methylimidazolium acetate [bmim][acetate] ionic liquid is measured using a static high pressure equilibrium cell. The weight percents of MDEA and [bmim][acetate] are between 30- 50 and 5- 50%, respectively. The experiments are carried out at 323.15 and 348.15 K and in total pressure range of about 2-25 bar. The solubility data are demonstrated as acid gas partial pressures against its molality. The results illustrate that at low ionic liquid weight percent, increasing [bmim][acetate] can lead to diminish both acid gases solubility. This is always true for CO2 solubility at high weight percent of the ionic liquid but not always for H2S. In fact, enhancing of H2S solubility will occur in lower temperaturesbecause [bmim][acetate] is very selective toward H2S in presence of CO2. At high weight percent of IL physical absorption is taking place while the physical absorption probability decreases at higher temperatures so that the H2S solubility declines. Also it can be deduced from the data that the present ionic liquid shows more selectivity toward H2S.

Keywords:

Acid gas solubility , Alkanolamine , N-methyldiethanolamine , MDEA , Ionic liquid , [bmim][acetate]