(558bs) Regeneration Energy and Thermal Stability Studies of Amine-Based Deep Eutectic Solvents for Carbon Dioxide Capture

In this study, the specific heat capacities, heat of absorption, and extent of chemical absorption of CO₂ of three choline chloride-amine deep eutectic solvents (DESs) were determined experimentally and compared with aqueous amine and solid adsorbents. Moreover, the thermal stability of tetrabutylammonium bromide (TBAB) and benzyltriethylammonium chloride (BTEAC) based DESs was studied. The estimation of these quantities would aid in the determination of the thermal stability and regeneration energy requirements of the amine based DESs. This study is significant because the conventional aqueous amines are known to exhibit a prohibitive regeneration energy, and the instability of the solvents under CO₂ absorption conditions has been widely reported. The specific heat capacity of the amine based deep eutectic solvents are all lower than that of the aqueous amine solution of MEA 30% weight. Moreover, when compared to solid adsorbents, amine based DESs exhibited a good level of closeness in the specific heat capacity and sometimes having less specific heat as in the case of ChCl-MDEA. Furthermore, HPLC analysis of the DESs before and after CO₂ absorption revealed that only some of the amine in the DES reacted with absorbed CO₂. This is an indication that both chemical and physical absorption of CO₂ existed. This result is of importance since physical absorption of the carbon dioxide will significantly reduce the regeneration energy requirements for the capture process. The Thermo-Gravimetric Analysis (TGA) results showed that the DESs studied in this work are more stable under temperature conditions when compared to the conventional aqueous solution of amines.