CO₂ Capture Efficiency, Corrosion Properties, and Ecotoxicity Evaluation of Amine Solutions Involving Newly Synthesized Ionic Liquids

Abstract

The CO 2 capture efficiency of nine newly synthesized ionic liquids (ILs), both in their pure states as well as in binary and ternary systems with water and amines, was investigated. The study encompassed ILs with fluorinated and tricyanomethanide anions as well as ILs that interact chemically with CO 2 such as those with amino acid and acetate anions. Compared to amines, some of the novel ILs exhibited a majority of important advantages for CO 2 capture such as enhanced chemical and thermal stabilities and negligible vapor pressure; the previous features counterbalance the disadvantages of lower CO 2 absorption capacity and rate, making these ILs promising CO 2 absorbents that could partially or totally replace amines in industrial scale processes. In addition to their ability to capture CO 2 , important issues including corrosivity and ecotoxicity were also examined. A thorough investigation of the capture efficiency and corrosion properties of several solvent formulations proved that some of the new ILs encourage future commercial-scale applications for appropriate conditions. ILs with a tricyanomethanide anion confirmed a beneficial effect of water addition on the CO 2 absorption rate (ca. 10-fold) and capacity (ca. 4-fold) and high efficiency for corrosion inhibition, in contrast with the negative effect of water on the CO 2 absorption capacity of ILs with the acetate anion. ILs with a fluorinated anion showed high corrosivity and an almost neutral effect of water on their efficiency as CO 2 absorbents. ILs having amino acid anions presented a reduced toxicity and high potential to completely replace amines in solutions with water but, in parallel, showed thermal instability and degradation during CO 2 capture. Tricyanomethanide anion-based ILs had a beneficial effect on the capture efficiency, toxicity, and corrosiveness of the standard amine solutions. As a consolidated output, we propose solvent formulations containing the tricyanomethanide anion-based ILs and less than 10 vol % of primary or secondary amines. These solvents exhibited the same CO 2 capture performance as the 20−25 vol % standard amine solutions. The synergetic mechanisms in the capture efficiency, induced by the presence of the examined ILs, were elucidated, and the results obtained can be used as guidance for the design and development of new ILs for more efficient CO 2 capture.

Novel pressure and temperature swing processes for CO2 capture using low viscosity ionic liquids

“…It is suitable for hydrocarbons and organic solvents, except for chlorinated solvents. For tricyanomethanide ILs it is recommended [30] to use standard steel 304, which has a higher resistance to corrosion and is more expensive than CS.…”

Thermophysical properties of imidazolium tricyanomethanide ionic liquids: experiments and molecular simulation

“…2,49,50 Some thermophysical properties for imidazolium [TCM] À -based ILs have been recently reported in the literature. 56, 57 Neves et al 58 performed for the first time a consistent and comprehensive structure-property study for a set of imidazolium-based ILs with cyano-functionalized anions, where the effect of the anion on the studied properties was investigated.…”

Microscopic study of the corrosion behaviour of mild steel in ionic liquids for CO2 capture applications

“…8,16 Sodium molybdate Na 2 MoO 4 $2H 2 O ($99.0% purity, Sigma-Aldrich) was used to study its inhibition effect with [BHC]BTA. 8,16 Sodium molybdate Na 2 MoO 4 $2H 2 O ($99.0% purity, Sigma-Aldrich) was used to study its inhibition effect with [BHC]BTA.…”

“…salts with melting points below 100 C, have received increasing academic and industrial interest since their properties may be tuned by selection of an appropriate combination of anion and cation. 8 In many applications, ILs will be in contact with metallic materials such as pipes, vessels and reaction chambers, which necessitates good understanding of their interactions with the metallic materials used for construction of installations that operate in IL-based environments. Their major properties may be summarised as follows: 1 (i) the cation is quite large and the anion is not necessarily large (it may comprise one atom); (ii) they are good solvents for a large variety of organic and inorganic substances; (iii) the vapour pressure is negligible, with a value of the order of 10 À11 to 10 À10 mbar; 2 (iv) the viscosity is typically below 100 cP; (v) the liquids have relatively high specic conductivities, usually up to 10 mS cm À1 ; and (vi) a wide electrochemical window is displayed, typically ranging from 4 to 5 V, and up to 7 V for some ILs.…”