Effect of Water Addition on CO2 Solubility of Glycol-Based Deep Eutectic Solvents

Abstract

Secure, affordable, and reliable energy supplies are essential for economic growth, but a tremendous increase in CO2 emission is the cause of serious concern. Conventionally, aqueous amines are used for CO2 capture in a variety of different capture. However, these solvents suffer from a problem such as degradation of amine absorbents, evaporative loss, and high regeneration energy requirement. Deep Eutectic Solvents (DESs) similar to that of Ionic Liquids are omnipotent to capture CO2. They constitute hydrogen bond donor (HBD) and Hydrogen Bond Acceptor (HBA) resulting in a low melting point mixture; due to the formation of their intermolecular hydrogen bonds. DESs have a wide range of applications in different engineering fields due to the combinations and ratios of HBA and HBD. Charge delocalization in DESs is the main reason behind the low melting points then of the individual constituents. The Hydrogen bonds play a significant role in the more effective binding of CO2 molecules by DESs compared to that of Ionic Liquids(ILs). In this work, different types of amine and glycol-based deep eutectic solvents were synthesized and the effect of water addition on CO2 solubility is studied. Tetrabutylammonium bromide was used as a hydrogen bond acceptor and different hydrogen bond donors were used. DESs were further analyzed by adding 10 wt. %, 20 wt. %,30 wt% of water. For measuring the CO2 solubility pressure drop method was used where a fixed amount of solvent is charged to the high-pressure equilibrium cell and a decrease in the pressure is monitored at regular intervals of time. The results showed that the synthesized DESs can absorb CO2. In general, amine-based solvents have shown higher CO2 absorption as compared to glycol-based solvents. Further, the addition of water has a different effect on glycol and amine-based DESs.