Betaine-based deep eutectic solvents with diol, acid and amine hydrogen bond donors for carbon dioxide absorption

Deep eutectic solvents (DESs) are known as alternative green solvents due to their ease of synthesis, availability, biodegradability and negligible volatility. DESs consisted of betaine as the hydrogen bond acceptor with 1,2-propanediol, levulinic acid and methyl diethanolamine (MDEA) as the hydrogen bond donors, were prepared in 1:3 and 1:6 molar ratios. The carbon dioxide solubilities in these DESs were determined using a volumetric apparatus at 313.15 K and 6 bar. The results show that CO2 solubilities in betaine-based DESs are higher than the reported CO2 solubilities in choline chloride-based DESs, for DESs having the same hydrogen bonding donor and an identical or similar composition. The viscosity and polarity of hydrogen bond donors affected the ability of deep eutectic solvent to absorb carbon dioxide. The betaine-MDEA deep eutectic solvent, with molar ratio of 1:6, has the highest absorption capacity of 0.0814 mol CO2/mol DES, measured at 313.15 K and 6 bar.