Solubility and Mass Transfer Performance of Ethane and n-Butane in Menthol and Decanoic Acid Deep Eutectic Solvent

Abstract

The absorption performance and mechanism of the deep eutectic solvent (DES), composed of menthol and decanoic acid, were investigated. The solubility of volatile organic compounds (VOCs) in the DES was studied through saturation solution experiments, wherein the solubility of ethane and n-butane increases with a decrease in temperature and increasing pressure. Henry's law constants of ethane and n-butane in the DES at 288.2 K were 2.089 and 0.136 MPa, respectively, demonstrating the high solubility for light hydrocarbons that surpasses or equals that of ionic liquids. The mass transfer and regeneration performance of the DES were investigated by using dynamic bubbling experiments. Results demonstrated that the removal rate of both ethane and n-butane increased as the gas flow rate decreased and the VOC concentration in the model gas increased. Specifically, the removal rate of ethane reached 99.50% at a temperature of 293.2 K, a VOC concentration VOC of 10,000 μmol/mol, and a gas flow rate of 30 mL/min, while the removal rate of n-butane was higher than that of ethane under the same conditions, achieving a removal rate exceeding 99.99%. Furthermore, no significant decrease in the removal rate for n-butane was observed during the four regeneration processes. Interaction energies between the VOC molecule and DES were calculated using the quantum chemistry method. It was found that the interactions between the VOC molecule and DES are primarily attributed to dispersion attractive effects which belong to weak interactions; therefore, the absorption of light hydrocarbon by the DES belongs to a physical process. The DES has been proven to be effective for the recovery of light hydrocarbons, providing a promising approach to address the key challenge in comprehensive treatment of VOCs in the petrochemical industry.