Solubility of Carbon Dioxide in Carboxylic Acid-Based Deep Eutectic Solvents

The solubility of carbon dioxide (CO2) in three carboxylic acid-based deep eutectic solvents (DESs) constituted by tetrabutylammonium bromide (TBABr)/octanoic acid (1:2) or TBABr/decanoic acid (1:2) or (DL-menthol/dodecanoic acid) (2:1) was measured using a high-pressure variable volume cell at a temperature ranging from 293.15 to 373.15 K and a pressure up to 122.9 bar. Under 40 bar and at 313.15 K, the best CO2 solubility (2.53 mol(CO2) kg(DES)(-1)) was found with TBABr/decanoic acid (1:2). Experimental measurements were correlated using the PC-SAFT strategy. In this work, the DESs are defined as pseudo-pure components and their PC-SAFT parameters were obtained by fitting to the density data of pure DESs. It was found that the PC-SAFT equation of state represents the CO2 solubility in carboxylic acid-based DESs with good accuracy.