Reversible absorption of CO2 by diethylenetriamine hydrochloride and ethylene glycol mixtures with high capacity and low viscosity

In this work, three kinds of ammonium salts containing chloride ion [DETA]·nCl (n = 1, 2, 3) were synthesized via the reactions between diethylenetriamine (DETA) and hydrochloric acid. And ethylene glycol (EG) was chosen as a solvent to dissolve [DETA]·nCl to prepare liquid hybrid absorbents for the capture of CO2. Effects of amount of chloride ion, absorption temperature, CO2 partial pressure and [DETA]·Cl concentration on the absorption of CO2 were systematically studied. It has been found that [DETA]·Cl (1) + EG (2) (mole ratio of EG to [DETA]·Cl R = 4.0) shows a high absorption capacity of CO2. The mole ratio of CO2 to [DETA]·Cl could reach 0.765 (0.0868 g CO2/g absorbent) at 50 °C under atmospheric pressure. Importantly, the viscosity of [DETA]·Cl (1) + EG (2) (R = 4.0) is quite low (105.3 mPa s) even when it is saturated with CO2 at 50 °C. Finally, [DETA]·Cl (1) + EG (2) (R = 4.0) could be reused to absorb CO2 for five times without obvious loss of absorption capacity. The result indicates that [DETA]·Cl (1) + EG (2) is a promising reversible absorbent for the capture of CO2.