Thermodynamic and molecular insights into the absorption of H2S, CO2, and CH4 in choline chloride plus urea mixtures

• Published in: AIChE journal Vol. 65; no. 5
• Main Authors: Liu, Fujian, Chen, Wei, Mi, Jinxing, Zhang, Jia‐Yin, Kan, Xun, Zhong, Fu‐Yu, Huang, Kuan, Zheng, An‐Min, Jiang, Lilong
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.05.2019; American Institute of Chemical Engineers
• Subjects: Absorption; Carbon dioxide; Chlorides; Choline; Computer simulation; Data processing; deep eutectic solvents; Enthalpy; Gas absorption; Gas separation; Henrys law; Hydrogen sulfide; Mathematical analysis; Methane; Monte Carlo simulation; Natural gas; natural gas upgrading; Organic chemistry; Quantum chemistry; selective gas absorption; Solubility; Solvents; theoretical calculation; thermodynamic analysis; Thermodynamic properties; Urea
• ISSN: 0001-1541; 1547-5905
• DOI: 10.1002/aic.16574

Deep eutectic solvents (DESs) are a class of promising media for gas separation. In order to examine the potential application of DESs for natural gas upgrading, the solubilities of H2S, CO2, and CH4 in choline chloride (ChCl) plus urea mixtures were measured in this work. The solubility data were correlated with Henry's law equation to calculate the thermodynamic properties of gas absorption processes, such as Henry's constants and enthalpy changes. Grand‐canonical Monte Carlo simulations and quantum chemistry calculations were also performed to examine the mechanism of gas absorption processes. It is found that the absorption of H2S in ChCl + urea mixtures is governed by the hydrogen‐bond interaction between Cl of ChCl and H of H2S, whereas the absorption of CO2 and CH4 in ChCl+urea mixtures is governed by the free volume of solvents. Based on the different behavior of gas absorption, high H2S/CO2, H2S/CH4, and CO2/CH4 selectivities can be achieved by adjusting the ratio of ChCl/urea in mixtures.