Carbon Dioxide Capture with Ionic Liquids and Deep Eutectic Solvents: A New Generation of Sorbents

Abstract

High cost and high energy penalty for CO uptake from flue gases are important obstacles in large-scale industrial applications, and developing efficient technology for CO capture from technical and economic points is crucial. Ionic liquids (ILs) show the potential for CO separation owing to their inherent advantages, and have been proposed as alternatives to overcome the drawbacks of conventional sorbents. Chemical modification of ILs to improve their performance in CO absorption has received more attention. Deep eutectic solvents (DESs) as a new generation of ILs are considered as more economical alternatives to cope with the deficiencies of high cost and high viscosity of conventional ILs. This Review discusses the potential of functionalized ILs and DESs as CO sorbents. Incorporation of CO -philic functional groups, such as amine, in cation and/or anion moiety of ILs can promot their absorption capacity. In general, the functionalization of the anion part of ILs is more effective than the cation part. DESs represent favorable solvent properties and are capable of capturing CO , but the research work is scarce and undeveloped compared to the studies conducted on ILs. It is possible to develop novel DESs with promising absorption capacity. However, more investigation needs to be carried out on the mechanism of CO sorption of DESs to clarify how these novel sorbents can be adjusted and fine-tuned to be best tailored as optimized media for CO capture.

Phosphonium‐Based Ionic Liquids Used as Reagents or Catalysts

“…The capture and separation of CO 2 was achieved with conventional ILs such as imidazolium, pyridinium, ammonium and phosphonium salt with various type of anions, functionalized ILs and IL blending solvents. The relationship between IL structures, physical properties and CO 2 absorption/desorption results (i. e. solubility, selectivity and desorption enthalpy) has significance in the designing of ILs structure with good selectivity, thermal stability, and low viscosity . A series of dual amino functionalized phosphonium ionic liquids (3‐aminopropyl)tributylphosphonium amino acid salts ( 29 ) with relatively low viscosity: aP 4443 ‐Gly, aP 4443 ‐Ala, aP 4443 ‐Val, and aP 4443 ‐Leu was investigated for CO 2 absorption (Scheme ) …”

The Virtuous CO2 Circle or the Three Cs: Capture, Cache, and Convert

“…Another important disadvantage is the high viscosity. These drawbacks and the high prices restrict their industrial applications [50].…”

“…The main CO 2 -philic groups are fluorine atoms, amine, and carbonyl groups. Ionic liquids containing amine or carboxylate moieties are considered as chemical scrubbing solvents and have advantages for CO 2 separation under low pressure; aminefunctionalized ionic liquids exhibit better selectivity, because the electrophilic properties of CO 2 functionalization of the anion part are usually more effective [50].…”

Structural Elucidation of Covalent Organic Polymers (COP) and Their Linker Effect on Gas Adsorption Performance via Density Functional Theory Approach

“…Regardless of either adsorbents or absorbents, capture materials must include the characteristics of null (or minimum) toxicity, low corrosivity, low regeneration cost and low degradation properties . There is an increasing interest on some new alternative materials that are considered as alternative CO 2 capture solvents such as ionic liquids and deep eutectic solvents …”