135
Besides, the knowledge of solubility data is essential to calculate phase equilibria for the design of chemical engineering processes and of course to determine the
fate of substances in the environment. The scientific and technological aspects are
often associated with each other, for example, in the search for new strategies to
improve the choice of novel solvents or separation media for chemical reactions or
industrial processes. In a society demanding less hazardous and more efficient
chemistry, the choice of alternative solvents (acceptable both from an economical
and environmental point of view) for reactions or separations is regarded as one of
the promising ways for sustainable development.
Mixtures formed by salts and molecular compounds that can act as hydrogen
bond donors may often lead to non-ideal binary mixtures that form eutectics, with
melting temperatures significantly lower than that of the predictions for their ideal
eutectic mixture. These mixtures are often designated, after the pioneer work by
Abbott et al. (2003, 2004), as deep eutectic solvents, or DES, and are considered as
promising liquids with low environmental impact for different applications.
Amongst these applications, electroplating, biomass conversion, atmospheric air
remediation, liquid-liquid extraction, and gas separation using deep eutectic solvents are considered as promising alternatives to traditional approaches based on
conventional solvents.
In this chapter, we report the solubility of ten solutes, which are gaseous at room
temperature, in different deep eutectic solvents, considered as such by authors of the
publications mentioned. The gases reported include carbon dioxide (CO 2 ), carbon
monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO 2 ), hydrogen (H 2 ), hydrogen sulfide (H 2 S), sulfur dioxide (SO 2 ), nitrogen (N 2 ), ammonia (NH 3 ), and methane
(CH 4 ). Although some studies report the use of deep eutectic solvents for olefin/
paraffin gas separations (Jiang et al. 2017a, b, c; Deng et al. 2017b; Dou et al. 2018),
to our knowledge, the solubility of hydrocarbon gases other than methane has not
been studied in eutectic mixtures. Eighty-seven different eutectic mixtures were
studied with the ten different gases as reported in Tables 4.1 and 4.2. Carbon dioxide
is, by far, the most studied gas in deep eutectic solvents with more than 50 published
papers dealing with the experimental determination of the solubility at different
conditions of temperature and partial pressure of gas. Sulfur dioxide and ammonia
were also studied in 40 and 30 eutectic mixtures, respectively. All the other seven
gases are much less studied in deep eutectic solvents.
The majority of the studies so far consider that the gases NH 3 , H 2 S, CO, CH 4 ,
NO 2 , and N 2 dissolve in the eutectic mixtures. The absorption capacity of deep
eutectic solvents for the different gases varies greatly, and values of K H varying
between 367.7 × 10
5
Pa for CH 4 in [Ch]Cl:U (1:1.5) at 353.2 K (Liu et al. 2019) and
0.0167 × 10
5
Pa for NO in [P 4444 ]Br:EG (1:50) at 323.15 K (Dou et al. 2019) were
found. One of the reasons for this major variety of Henry’s law constants is the fact
that the absorption process for some gases can be only a physical process (e.g., N 2
(Wu et al. 2015), CO (Wu et al. 2015), CH 4 (Wu et al. 2015; Liu et al. 2019)) while
for others it might be both physical and chemical (as reported for SO 2 (Zhao et al.
2018; Chen et al. 2018; Cui et al. 2019a) in [BMIm]Cl:Ac (1:1) (Zhao et al. 2018)
and Pip:Gly (1:6) (Cui et al. 2019a), NO (Sun et al. 2017a; Dou et al. 2019) in
4 Solubility of Gases in Deep Eutectic Solvents
Besides, the knowledge of solubility data is essential to calculate phase equilibria for the design of chemical engineering processes and of course to determine the
fate of substances in the environment. The scientific and technological aspects are
often associated with each other, for example, in the search for new strategies to
improve the choice of novel solvents or separation media for chemical reactions or
industrial processes. In a society demanding less hazardous and more efficient
chemistry, the choice of alternative solvents (acceptable both from an economical
and environmental point of view) for reactions or separations is regarded as one of
the promising ways for sustainable development.
Mixtures formed by salts and molecular compounds that can act as hydrogen
bond donors may often lead to non-ideal binary mixtures that form eutectics, with
melting temperatures significantly lower than that of the predictions for their ideal
eutectic mixture. These mixtures are often designated, after the pioneer work by
Abbott et al. (2003, 2004), as deep eutectic solvents, or DES, and are considered as
promising liquids with low environmental impact for different applications.
Amongst these applications, electroplating, biomass conversion, atmospheric air
remediation, liquid-liquid extraction, and gas separation using deep eutectic solvents are considered as promising alternatives to traditional approaches based on
conventional solvents.
In this chapter, we report the solubility of ten solutes, which are gaseous at room
temperature, in different deep eutectic solvents, considered as such by authors of the
publications mentioned. The gases reported include carbon dioxide (CO 2 ), carbon
monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO 2 ), hydrogen (H 2 ), hydrogen sulfide (H 2 S), sulfur dioxide (SO 2 ), nitrogen (N 2 ), ammonia (NH 3 ), and methane
(CH 4 ). Although some studies report the use of deep eutectic solvents for olefin/
paraffin gas separations (Jiang et al. 2017a, b, c; Deng et al. 2017b; Dou et al. 2018),
to our knowledge, the solubility of hydrocarbon gases other than methane has not
been studied in eutectic mixtures. Eighty-seven different eutectic mixtures were
studied with the ten different gases as reported in Tables 4.1 and 4.2. Carbon dioxide
is, by far, the most studied gas in deep eutectic solvents with more than 50 published
papers dealing with the experimental determination of the solubility at different
conditions of temperature and partial pressure of gas. Sulfur dioxide and ammonia
were also studied in 40 and 30 eutectic mixtures, respectively. All the other seven
gases are much less studied in deep eutectic solvents.
The majority of the studies so far consider that the gases NH 3 , H 2 S, CO, CH 4 ,
NO 2 , and N 2 dissolve in the eutectic mixtures. The absorption capacity of deep
eutectic solvents for the different gases varies greatly, and values of K H varying
between 367.7 × 10
5
Pa for CH 4 in [Ch]Cl:U (1:1.5) at 353.2 K (Liu et al. 2019) and
0.0167 × 10
5
Pa for NO in [P 4444 ]Br:EG (1:50) at 323.15 K (Dou et al. 2019) were
found. One of the reasons for this major variety of Henry’s law constants is the fact
that the absorption process for some gases can be only a physical process (e.g., N 2
(Wu et al. 2015), CO (Wu et al. 2015), CH 4 (Wu et al. 2015; Liu et al. 2019)) while
for others it might be both physical and chemical (as reported for SO 2 (Zhao et al.
2018; Chen et al. 2018; Cui et al. 2019a) in [BMIm]Cl:Ac (1:1) (Zhao et al. 2018)
and Pip:Gly (1:6) (Cui et al. 2019a), NO (Sun et al. 2017a; Dou et al. 2019) in
4 Solubility of Gases in Deep Eutectic Solvents