Ionic-Liquid-Assisted Capture of Volatile Low-Carbon Alcohols in Printing Plant Exhaust Gas

In green and sustainable chemical development, the efficient capture of volatile organic compounds (VOCs) with novel green solvents is recognized as an excellent potential research direction. This study proposes a novel method to efficiently absorb alcohols (ethanol, n-propanol, and isopropyl alcohol) in VOCs emitted from printing factories by ionic liquids (ILs). The COSMO-RS model screened 256 ILs with Henry's law constant and selectivity coefficient as separation performance indexes. 1-(2-Hydroxyethyl)-3-methylimidazolium hexafluorophosphate ([HEMIM][PF6]) is the most potential absorbent. The absorption performance and interaction mechanism of [HEMIM][PF6] on ethanol, n-propanol, and isopropyl alcohol were investigated with a combination of calculation thermodynamics, molecular dynamics, and gas absorption experiments. The alcohol absorption experiments and regeneration experiments of ILs were performed at different IL flow rates, and the results demonstrated that ILs possessed excellent stability and regenerative properties. The excess enthalpy analysis demonstrated the thermodynamic feasibility of capturing alcohol molecules with ILs. Molecular surface electrostatic potential analysis was performed to obtain binding sites for intermolecular interactions. The spatial distribution function revealed the spatial distribution of ILs around alcohol molecules from the perspective of clustered macromolecules. This work provides theoretical insights into molecular thermodynamics and kinetics for developing novel ILs for VOC purification.