Condensable Gases Capture with Ionic Liquids

Condensable gases are the sum of condensable and volatile
steam
or organic compounds, including water vapor, which are discharged
into the atmosphere in gaseous form at atmospheric pressure and room
temperature. Condensable toxic and harmful gases emitted from petrochemical,
chemical, packaging and printing, industrial coatings, and mineral
mining activities seriously pollute the atmospheric environment and
endanger human health. Meanwhile, these gases are necessary chemical
raw materials; therefore, developing green and efficient capture technology
is significant for efficiently utilizing condensed gas resources.
To overcome the problems of pollution and corrosion existing in traditional
organic solvent and alkali absorption methods, ionic liquids (ILs),
known as “liquid molecular sieves”, have received unprecedented
attention thanks to their excellent separation and regeneration performance
and have gradually become green solvents used by scholars to replace
traditional absorbents. This work reviews the research progress of
ILs in separating condensate gas. As the basis of chemical engineering,
this review first provides a detailed discussion of the origin of
predictive molecular thermodynamics and its broad application in theory
and industry. Afterward, this review focuses on the latest research
results of ILs in the capture of several important typical condensable
gases, including water vapor, aromatic VOCs (i.e., BTEX), chlorinated
VOC, fluorinated refrigerant gas, low-carbon alcohols, ketones, ethers,
ester vapors, etc. Using pure IL, mixed ILs, and IL + organic solvent
mixtures as absorbents also briefly expanded the related reports of
porous materials loaded with an IL as adsorbents. Finally, future
development and research directions in this exciting field are remarked.