Solubilities and Thermodynamic Properties of CO2 in Four Azole

Jun 1, 2018 - The solubility data of CO2 in four azole-based deep eutectic solvents (DESs), prepared from azoles (imidazole, Im; 1,2,4-triazole,Tri) a...
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Article Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Solubilities and Thermodynamic Properties of CO2 in Four AzoleBased Deep Eutectic Solvents Xiaofeng Li,*,† Xiaobang Liu,‡ and Dongshun Deng*,‡ †

Department of Chemistry, Zhejiang University, Hangzhou 310027, China College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, China

‡

ABSTRACT: The solubility data of CO2 in four azole-based deep eutectic solvents (DESs), prepared from azoles (imidazole, Im; 1,2,4-triazole,Tri) and acetylcholine chloride (ACC), were reported at temperatures of 303.15, 313.15, 323.15, and 333.15 K under a pressure range of (20.0- 600.0) kPa using the isochoric saturation method. Henry’s constants and thermodynamic properties of standard Gibbs free energy, enthalpy, and entropy changes of CO2 dissolution were derived by correlating the data. Results demonstrated that ACC-Im DESs (Hm = 1.91−4.46 MPa·kg·mol−1) possess higher capacities of CO2 than CC-Tri ones (Hm = 2.66- 4.58 MPa·kg·mol−1). The CO2 solubility increased with rising pressure, mole ratio of Im to ACC, and decreasing temperature. All the obtained enthalpies of solution were negative. Furthermore, the comparison of dissolution capacities between present DESs and other DESs as well as some ionic liquids in the literature was conducted.

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concept of DESs in 2003,8 attention to the DESs mainly developed the scope of the HBA and HBD and their utilization.9 DESs were also reported as CO2 absorbents in the literature. For example, Li’s group10−12 reported CO2 solubility in DESs made from choline chloride and glycerol, or ethylene glycol, or urea at moderate pressures (approximately 6.3 MPa and 303.15−343.15 K). They also investigated water as an antisolvent to regenerated CO2 saturated aqueous reline solutions (choline chloride−urea DES) and monoethanolamine as a functional component to enhance the absorption capacity of reline.13,14 Francisco et al.15 reported natural choline chloride−lactic acid (1:2 mol ratio) DES to absorb CO2. Li et al.16 presented the solubilities of CO2 in a choline chloride urea eutectic mixture at elevated pressures (up to xCO2 = 0.301 at 12.5 MPa and 313.15 K). In our previous reports,17−19 the solubility of CO2 in the DESs composed of choline chloride and HBDs such as phenol, dihydric alcohols, biobased furfuryl alcohol, and levulinic acid were presented. Recently, four azole-based DESs (1,2,4-triazole, Tri, and imidazole, Im) and acetylcholine chloride (ACC) were used to capture SO2 with preferable results than common ILs and DESs due to their weak alkalinity.20 Because CO2 is also an acidic gas as similar to SO2, herein the above-mentioned DESs were further explored as potential absorbents for CO2. Experimental measurement was carried out using the isochoric saturation method. Henry’s law model was further used to correlate the solubility data with the temperature and pressure. To better understand the dissolving behavior of CO2 in DESs,

INTRODUCTION The emission of carbon dioxide (CO2) due to growing combustion of fossil fuels has attracted much attention. Increasing CO2 concentration has caused damage to the environment and ecosystem.1 Therefore, how to reduce CO2 at the source is particularly important for the sustainable development and has attracted global attention. Carbon capture and sequestration (CCS) is the main method to realize the reduction of CO2 emission in recent years.2 Postcombustion carbon capture mainly involved commercial amine-based absorbents. Although they can remove CO2 quickly and effectively, their drawbacks such as second pollution, equipment corrosion, and intensive energy consumption are also troublesome. 3 Thus, developing environmentally friendly CO 2 absorbents with low overall cost is always imperative. With the emerging of ionic liquids (ILs) in the past 20 years, the attractive properties of negligible volatility, good stability, and mutable structure entitle them as “promising” mediums in many chemical reactions and separation processes.4 As for acidic gas capture field, the literature is extensive and rich.5,6 However, the preparation of ILs is far from being atomically economic. The high price of ILs is another challenge for moving the IL commercial gas absorbents from lab research to industrial application. Encouragingly, deep eutectic solvents (DESs), noted as second generation ILs, are presented as alternatives for ILs in many fields.7 DESs have solvent properties and merits similar to common ILs but overcome several of the limitations of ILs. Moreover, DESs can be obtained on a large-scale by directly blending a hydrogen-bond donor (HBD) with a hydrogen-bond acceptor (HBA) in a suitable composition that is industrially available, inexpensive, and completely characterized. Since Abbott proposed the © XXXX American Chemical Society

Received: February 1, 2018 Accepted: May 24, 2018

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DOI: 10.1021/acs.jced.8b00098 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

molality) at each temperature (T) and partial pressure of CO2 (p). Figures 1 and 2 illustrated the pressure-dependence of CO2 solubility data in ACC-Im (1:2) at various temperatures. Figure 3 presented the solubilities of CO2 in four azole-based DESs at 303.15 K. As can be seen from three figures, CO2 solubility in the DESs demonstrated linear dependence with increasing pressure and decreasing temperature. Such behavior means that CO2 is absorbed by DESs through a physical dissolution behavior. The system errors from temperature, pressure, mass, and volume contribute to the uncertainties of the measurement. Then, the relative standard uncertainty of CO2 solubility can be derived as follows according to the theory for uncertainty,21

the thermodynamic properties of dissolution enthalpy, dissolution entropy, and standard Gibbs free energy were further calculated according to Henry’s law constants at different temperatures.

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EXPERIMENTAL SECTION Chemicals. CO2 (>99.95%) was purchased from Jingong Special Gas Co., Ltd. Anhydrous ACC (0.990, mass fraction, the same below), imidazole (0.990) and 1,2,4-triazole (0.995) were AR grade and used as supplied by Shanghai Aladdin Chemical Company. Table 1 summarized the used chemicals

Table 1. Description of Chemicals Used in Present Work chemical

abbreviation

CASRN

source

carbon dioxide

CO2

124-38-9

acetylcholine chloride

ACC

60-31-1

imidazole

Im

288-32-4

1,2,4-triazole

Tri

288-88-0

Jingong Special Gas Co., Ltd. Jinan Hualing Pharmaceutical Co., Ltd. Shanghai Aladdin Chemical Reagent Co., Ltd. Shanghai Aladdin Chemical Reagent Co., Ltd.

mass fraction purity

ur(x) =

>0.9995

=

>0.990

mCO2 = nCO2 /w

⎛ u(nCO ) ⎞2 ⎛ u(nCO ) + u(nDES) ⎞2 2 ⎟ 2 ⎜⎜ ⎟⎟ ⎟ + ⎜⎜ n ⎝ nCO2 ⎠ ⎝ ⎠ CO2 + nDES

u(n)2 + u(n1)2 + u(n2)2 + u(nDES)2 u(n)2 + u(n1)2 + u(n2)2 + 2 nCO2 (nCO2 + nDES)2

(3)

≥0.990

u r (m) =

≥0.995

=

along with their purities and sources. An electronic balance (Mettler-Toledo AL204) with the standard uncertainty of 0.0002 g was applied to weight the mass of the materials. The DESs were prepared by directly mixing ACC with Im or Tri in an airtight bottle at 353 K and ambient pressure until a homogeneous and transparent liquid mixture was formed. Then, the prepared DESs were further dried for 48 h under vacuum and 353 K. The water content of each DES was less than 1.5 × 10−3 (mass fraction), as analyzed by the Karl Fischer method (SF-3 Karl Fischer Titration, Zibo Zifen Instrument Co. Ltd.). Apparatus and Procedures. CO2 solubilities in four DESs were measured using an isochoric saturation method. The experimental apparatus and procedures were described in detail in our previous work.18 The saturated vapor pressure of DES was far less than the standard uncertainty of the pressure transmitter and therefore was neglected. When gas−liquid equilibrium was reached, the liquid phase molality (mCO2) and mole fraction (xCO2) of CO2 were applied to express the solubilities of CO2 at equilibrium pressure (p) and temperature (T) as xCO2 = nCO2 /(nCO2 + nDES)

u(x) = x

u(m) m u(n)2 + u(n1)2 + u(n2)2 nCO2 2

+

∑ u(mDES)2 mDES2 (4)

where u(n1), u(n2), and u(n) can be calculated as follows, 2 ⎛ u(Vi ) ⎞2 ⎛ u(Ti ) ⎞2 ni ⎛ u(Pi) ⎞ u(ni) = ⎜ ⎟ +⎜ ⎟ +⎜ ⎟ R ⎝ Pi ⎠ ⎝ Vi ⎠ ⎝ Ti ⎠

(5)

and u(nDES) is estimated by u(nliq ) =

u(mDES) MW

(6)

The uncertainties of temperature, pressure, and volume are u(T) = 0.10 K, u(p) = 0.6 kPa, and u(V) = 0.05 mL, respectively. The uncertainty of mass is u(mDES) = 0.0002 g. Henry’s Law Constant. The physical solubility of gas in a solvent often obeys Henry’s law. Thus, Henry’s law constant Hx derived from mole fraction can be applied to quantitatively describe CO2 solubility of the present DESs as the following equation,22 Hx(p , T ) ≡ lim

x2 → 0

(1)

f 2liq (p , T , x 2) x2

(7)

f liq 2 (p,T,x2)

where denotes the fugacity of CO2 at equilibrium pressure (p), temperature (T), and mole fraction of CO2 (x2) in the liquid phase. According to the gas−liquid equilibrium criterion, liquid phase and vapor phase have the same fugacity of CO2 at the equilibrium. So,

(2)

where nCO2 is the mole number of CO2 dissolved into the DES, and nDES and w are the mole number and mass of the DES used in experiment, respectively.

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RESULTS AND DISCUSSION Solubility of CO2 in the DESs. The solubility data of CO2 in four DESs were determined at T = 303.15−333.15 K with 10 K intervals under the pressure range of 20.0−600.0 kPa. The DESs included ACC-Tri (1:1), ACC-Im (2:3), ACC-Im (1:2), and ACC-Im (1:3). Table 2 lists the solubility data of CO2 in four DESs (expressed as xCO2 for mole fraction and mCO2 for

f 2liq (p , T , x 2) = f 2vap (p , T , y2 ) = y2 pϕ2(p , T , y2 )

(8)

where f vap 2 (p,T,y2) is the fugacity of CO2 in the vapor phase, and y2 and ϕ2 are the mole fraction and fugacity coefficient of CO2 in the vapor phase, respectively. According to the literature,23 the saturated vapor pressures of DESs at present temperatures are too small to be neglected when compared with the B

DOI: 10.1021/acs.jced.8b00098 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Table 2. Solubility of CO2 in the DESs (xCO2, Mole Fraction; mCO2, Molality) at Different Temperatures (T) and Equilibrium Pressure (p)a T = 303.15 K

313.15 K

p/kPa

mCO2/(mol·kg−1)

xCO2

p/kPa

mCO2/(mol·kg−1)

63.7 107.6 192.5 288.3 382.9 496.8 587.7

0.0266 0.0424 0.0746 0.1097 0.1443 0.1859 0.2190

0.0033 0.0053 0.0093 0.0136 0.0178 0.0228 0.0267

56.3 101.6 219.6 366.6 444.5 523.9 572.2

0.0188 0.0321 0.0696 0.1158 0.1407 0.1658 0.1834

30.2 86.7 198.4 300.3 388.1 486.8 572.6

0.0068 0.0376 0.0854 0.1226 0.1558 0.1939 0.2282

0.0008 0.0042 0.0096 0.0137 0.0174 0.0215 0.0252

65.21 147.7 201.4 295.9 427.6 547.6

0.0233 0.0461 0.0622 0.0917 0.1381 0.1806

26.6 57.2 93.2 141.4 240.0 331.4 422.0 525.7 578.5

0.0183 0.0326 0.0473 0.0707 0.1175 0.1571 0.1964 0.2385 0.2607

0.0019 0.0034 0.0050 0.0074 0.0123 0.0164 0.0204 0.0246 0.0269

29.6 59.9 100.0 149.8 242.3 335.8 426.5 529.8 588.2

0.0090 0.0228 0.0367 0.0546 0.0871 0.1194 0.1518 0.1872 0.2079

52.8 91.0 200.3 291.4 385.4 478.6 567.6

0.0276 0.0561 0.1090 0.1580 0.1981 0.2490 0.2940

0.0027 0.0054 0.0104 0.0150 0.0187 0.0235 0.0276

29.2 59.9 87.8 140.2 233.6 337.0 424.5 522.8 583.6

0.0249 0.0349 0.0500 0.0710 0.1091 0.1465 0.1825 0.2198 0.2432

323.15 K xCO2

p/kPa

ACC-Tri (1:1) 0.0023 58.4 0.0040 147.7 0.0086 251.5 0.0143 340.7 0.0173 439.0 0.0204 542.0 0.0225 593.2 ACC-Im (2:3) 0.0026 29.8 0.0052 111.0 0.0070 148.6 0.0103 238.5 0.0154 329.1 0.0201 425.7 529.8 589.2 ACC-Im (1:2) 0.0010 27.5 0.0024 88.3 0.0039 142.6 0.0057 232.3 0.0091 331.6 0.0125 424.1 0.0158 526.8 0.0194 587.1 0.0216 ACC-Im (1:3) 0.0024 26.3 0.0034 58.0 0.0048 87.5 0.0068 139.1 0.0104 238.7 0.0139 337.1 0.0173 426.0 0.0208 531.0 0.0229 587.3

333.15 K

mCO2/(mol·kg−1)

xCO2

p/kPa

mCO2/(mol·kg−1)

xCO2

0.0153 0.0386 0.0614 0.0858 0.1101 0.1376 0.1508

0.0019 0.0048 0.0076 0.0106 0.0136 0.0170 0.0186

56.3 116.3 186.5 290.9 396.1 487.4 581.0

0.0131 0.0273 0.0408 0.0632 0.0845 0.1065 0.1276

0.0016 0.0034 0.0051 0.0079 0.0105 0.0132 0.0157

0.0131 0.0354 0.0433 0.0669 0.0900 0.1161 0.1433 0.1584

0.0015 0.0040 0.0049 0.0075 0.0101 0.0130 0.0160 0.0177

33.0 92.3 141.7 235.4 346.1 441.6 536.3 594.0

0.0096 0.0217 0.0320 0.0533 0.0770 0.0983 0.1199 0.1338

0.0011 0.0025 0.0036 0.0060 0.0087 0.0110 0.0134 0.0150

0.0082 0.0284 0.0445 0.0706 0.0990 0.1267 0.1584 0.1747

0.0009 0.0030 0.0047 0.0074 0.0104 0.0132 0.0165 0.0182

30.6 60.2 99.0 148.6 235.9 339.2 429.2 536.5 589.9

0.0086 0.0157 0.0253 0.0373 0.0584 0.0847 0.1074 0.1339 0.1476

0.0009 0.0017 0.0027 0.0039 0.0062 0.0089 0.0112 0.0140 0.0154

0.0144 0.0293 0.0379 0.0566 0.0862 0.1197 0.1483 0.1815 0.2007

0.0014 0.0028 0.0036 0.0054 0.0082 0.0114 0.0141 0.0172 0.0190

28.6 58.3 87.1 146.1 239.7 354.3 432.2 525.8 591.6

0.0084 0.0169 0.0243 0.0401 0.0646 0.0956 0.1172 0.1424 0.1600

0.0008 0.0016 0.0023 0.0038 0.0062 0.0091 0.0112 0.0136 0.0152

Standard uncertainties u are u(T) = 0.10 K, u(p) = 0.6 kPa, u(x) = 0.0007, u(m) = 0.006 mol·kg−1. The standard uncertainty of mole ratio of ACC to Tri or Im is 0.001. a

Figure 2. Solubility of CO2 (mole fraction) in DES of ACC-Im (1:2) at different temperatures: □, 303.15 K; ☆, 313.15 K; ○, 323.15 K; ◇, 333.15 K; , linear correlation.

Figure 1. Solubility of CO2 (molality) in DES of ACC-Im (1:2) at different temperatures: □, 303.15 K; ☆, 313.15 K; ○, 323.15 K; ◇, 333.15 K; , linear correlation.

C

DOI: 10.1021/acs.jced.8b00098 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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where n is the experimental numbers. Hi,m and Hi,x are Henry’s constant calculated from each single experimental data, respectively. Hx and Hm are above-mentioned Henry’s constant. For all the studied solutions, Henry’s constant increased (or the solubility of CO2 decreased) with increasing temperature. It is evident that ACC-Im DESs (Hm = 1.91−4.46 MPa·kg·mol−1) possess higher solubility of CO2 than ACC-Tri DES (Hm= 2.66−4.58 MPa·kg·mol−1). Furthermore, the solubility of CO2 in ACC-Im DESs increases with enhancing the mole ratio of Im to ACC. As a result, ACC-Im (1:3) DES gets the highest capture capacity of CO2 among four azole-based DESs. For further evaluation of the present DESs as CO2 capturers, Henry constants Hm at 313.15 K in four azole-based DESs and other DESs and some ILs reported in the literature were systematically compared. According to the definition of Henry’s constant, Hm can provide the uniform scale for dissolving ability. As can be seen from Table 4, azole-based DESs had

Figure 3. Solubility of CO2 (molality) in DESs of four azole-based DESs at 303.15 K: ○, ACC-Im (1:3); ☆, ACC-Im (1:2); □, ACC-Im (2:3); △, ACC-Tri (1:1).

Table 4. Comparison of Hm in Present DESs with Other DESs and Some ILs at 313.15 K

equilibrium partial pressure of CO2. Given the relative low pressure of CO2 at experiment, ϕ2(p,T) is basically close to unity. By combining eqs 7 and 8, Henry’s constant of CO2 in DESs can be derived as follows, f 2liq (p , T , x 2)

Hx(p , T ) = lim

x2

x2 → 0

≅

py2 ϕ2(p , T ) x2

≅

a

x2

x2 → 0

pCO

2

x2

(9)

On the basis of the same theory, Henry’s law constant Hm derived from molality is also deduced as the following equation, ⎡ f liq (p , T , m ) ⎤ py ϕ (p , T ) 2 ⎥≅ 2 2 Hm(p , T ) ≡ lim ⎢ 2 m2 → 0⎢ ⎥⎦ m2 m2 ⎣ p ≅ CO2 m2

(10)

where m2 is the molality of CO2 in the liquid phase. Hx and Hm were obtained as the slopes by linear fitting pressure vs mole fraction and molality of CO2, respectively. Table 3 listed the two kind of Henry’s constants of four azole-based DESs at various temperatures, with the values of Hx and Hm ranging from 20.27 to 39.77 and 1.91 to 4.58 MPa·kg mol−1, respectively. The average absolute deviation (AAD) of Henry constant was determined as following and listed in Table 3, 1 AAD ≡ ∑ |Hi , m − Hm| n n (11) AAD ≡

1 n

∑ |Hi ,x − Hx|

a

3.15 3.09 2.82 2.32 3.84 3.01 3.51 1.37 1.29 1.70 2.71 2.62 3.54 4.00 4.18 5.38 1.81

The standard uncertainty of mole ratio of ACC to Tri or Im is 0.001.

higher absorption capacities than DESs of ChCl + lactic acid15 or furfuryl alcohol18 or 1,4-butanediol,17 similar to three GCbased DESs,24 and lower than DESs of ChCl paired with urea,16,10 glycerols,12 and levulinic acid.18 Except for the absorption capacity, a new absorbent of DES for CO2 also needs screening the suitable HBA, HBD, and their mole ratio in order to acquire a satisfactory physicochemical property (e.g., viscosity, corrosivity, thermal, and chemical stability).25 Moreover, the studied DESs presented better dissolving abilities of CO2 than the ammonium IL of 2-hydroxy-N-(2-hydroxyethyl)-

(12)

n

a

ACC-Tri (1:1) ACC-Tri (1:1) ACC-Im (2:3)aACC-Im (2:3)a ACC-Im (1:2)a ACC-Im (1:2)a ACC-Im (1:3)aACC-Im (1:3)a nChCl:nGC = 1:5 nDH:nGC = 1:5 nACC:nGC = 1:5 nChCl:nurea = 1:2.5 nChCl:nurea = 1:2 nChCl:nglycerol = 1:2 nChCl:nethylene glycol = 1:2 nlevulinic acid: ncholine chloride = 3:1 nfurfuryl alcohol: ncholine chloride = 3:1 nChCl:nlactic acid = 1:2 nChCl: n1, 4‑butanediol = 1:4 [hhemel] [hmim][BF4]

pϕ2(p , T , y2 )

= lim

Hm/MPa·kg·mol−1

absorbents

Table 3. Henry’s Law Constants (Hx, Based on Mole Fraction; Hm, Based on Molality) of CO2 in the Azole-Based DESs at Different Temperaturesa Hm/MPa·kg·mol−1

Hx/MPa DESs ACC-Tri (1:1) ACC-Im (2:3) ACC-Im (1:2) ACC-Im (1:3) a

303.15 K 21.69 22.38 20.91 20.27

(0.83) (2.25) (2.05) (0.96)

313.15 K 25.58 27.70 27.07 24.53

(0.25) (0.99) (1.16) (3.64)

323.15 K 32.05 32.78 31.98 30.16

(0.61) (2.77) (0.75) (3.72)

333.15 K 37.14 39.77 38.24 38.76

(0.96) (1.72) (1.13) (0.80)

303.15 K 2.66 2.49 2.17 1.91

(0.08) (0.34) (0.20) (0.07)

313.15 K 3.15 3.09 2.82 2.32

(0.03) (0.13) (0.10) (0.33)

323.15 K 3.96 3.67 3.34 2.87

(0.07) (0.29) (0.11) (0.35)

333.15 K 4.58 4.46 4.00 3.69

(0.11) (0.17) (0.08) (0.08)

The standard uncertainty of mole ratio of ACC to Tri or Im is 0.001, the values in brackets are AAD. D

DOI: 10.1021/acs.jced.8b00098 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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N-methylethanaminium lactate ([hhemel]),26 while much less ability than the imidazolium IL of 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim][BF4]).27 As far as biodegradability, toxicity, and price are concerned, the studied DESs still have obvious superiority to the common ILs. Thermodynamic Properties. Thermodynamic properties are comprehensive parameters for describing the solubility of a gas in a solvent quantitatively. They provide information on probing the tendency and gas behavior in the solvent. For present azole-based DESs and CO2 mixtures, three thermodynamic properties are further derived as the following equations, ⎛ H (T , p) ⎞ ⎟ ΔdisG° = RT ln⎜ 0 ⎝ p ⎠

with CO2. The dissolving of CO2 into DESs follows a nonspontaneous behavior.

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Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Dongshun Deng: 0000-0001-7125-1833 Funding

Financial support from the Natural Science Foundation of Zhejiang Province (Grant LY17B060010) is highly appreciated. Notes

(13)

⎛ ∂ ln(H(T , p)/p ) ⎞ ⎟ ΔdisH ° = R ⎜ ∂(1/T ) ⎠p ⎝

(14)

⎛ V H ° − V G° ⎞ dis ⎟⎟ ΔdisS ° = ⎜⎜ dis T ⎝ ⎠

(15)

The authors declare no competing financial interest.

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0

Table 5. Calculated Standard Gibbs Free Energy (ΔdisG0), enthalpy (ΔdisH0) and entropy (ΔdisS0) of solutions at 0.1 MPa and 303.15 Ka

a

ΔdisG0/kJ·mol−1

ΔdisH0/kJ·mol−1

ΔdisS0/J·mol−1·K−1

ACC-Tri (1:1) ACC-Im (2:3) ACC-Im (1:2) ACC-Im (1:3)

8.27 8.10 7.76 7.43

−15.61 −16.13 −16.86 −18.33

−78.77 −79.93 −81.21 −84.97

REFERENCES

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where ΔdisG0, ΔdisH0, ΔdisS0 present the standard Gibbs free energy, enthalpy, and entropy changes for CO2 dissolution in DESs at standard pressure of p0 = 100 kPa, respectively. ΔdisH0 reflects the thermal effect of CO2 dissolution in DESs, while ΔdisS0 presents the change of order degree along with the CO2 dissolution into the DESs. Table 5 included the values of ΔdisG0, ΔdisH0, and ΔdisS0 at 303.15 K under standard pressure.

DESs

AUTHOR INFORMATION

The standard uncertainty of mole ratio of ACC to Tri or Im is 0.001.

Under each condition, the negative and relatively small values of ΔdisH0 mean that DESs dissolve CO2 through an exothermic process with weak intermolecular interaction between CO2 and DESs. The negative values of ΔdisS0 imply that the CO2-DES solution is more ordered than DES itself due to the dissolving of CO2 into DESs. As a comprehensive result, the positive values of ΔdisG0 demonstrate that DESs cannot dissolve CO2 spontaneously.

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CONCLUSION In the present contribution, new solubilities of CO2 in four azole-based DESs composed of imidazole or 1,2,4-triazole and acetylcholine chloride were reported. Henry’s law constant and thermodynamics properties of CO2 in DESs were derived on the basis of experimental data. Results suggested that the imidazole-based DESs demonstrate higher dissolving ability of CO2 than 1,2,4-triazole-based ones. Rising pressure or decreasing temperature has a positive effect on the solubility of CO2 in the DESs. Imidazole−acetylcholine chloride DESs with higher mole content of imidazole can enhance solubility E

DOI: 10.1021/acs.jced.8b00098 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

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DOI: 10.1021/acs.jced.8b00098 J. Chem. Eng. Data XXXX, XXX, XXX−XXX