Volatility of 2-(diethylamino)-ethanol and 2-((2-aminoethyl) amino) ethanol, a biphasic solvent for CO2 capture

Abstract

Amine volatility may be a critical problem with biphasic solvent for CO2 capture such as the blend of 2-(diethylamino)-ethanol (DEEA) and 2-((2-aminoethyl) amino) ethanol (AEEA). The Henry’s law constant (Ham) of DEEA and AEEA in water at 40 and 50 °C was measured using a hot gas FTIR. DEEA is 20–30 times more volatile than monoethanolamine (MEA) while AEEA is nearly non-volatile. At lean loading, the amine volatility is 327 ppm in 12 m DEEA and 1.1 ppm in 2.5 m AEEA at 40 °C. The NRTL model shows good consistency with the DEEA-H2O data for amine and water activity coefficients. Amine volatility in 12 m DEEA with 0 to 0.4 mol CO2/mol DEEA and in 2.5 m AEEA with 0 to 0.9 mol CO2/mol AEEA at 40 and 50 °C was also measured. DEEA partial pressure (PDEEA) increases with CO2 loading even though there is less free DEEA in the loaded solutions. The ionic reaction products of DEEA and CO2 increase the ionic strength and DEEA activity coefficient. The effect of ionic strength on the DEEA activity coefficient was confirmed with data for 12 m DEEA-H2O-KNO3 and 12 m DEEA-H2O-H2SO4. AEEA partial pressure (PAEEA) decreases with CO2 loading as AEEA is converted by the reaction with CO2 to other non-volatile species.