Efficient Absorption of SO2 by EmimCl-EG Deep Eutectic Solvents

Letter pubs.acs.org/journal/ascecg

Efficient Absorption of SO2 by EmimCl-EG Deep Eutectic Solvents Dezhong Yang,*,†,‡ Yanling Han,† Hongbin Qi,† Yingbin Wang,† and Sheng Dai*,‡,§ †

School of Science, China University of Geosciences, No. 29 Xueyuan Road, Haidian District, Beijing 100083, P.R. China Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States § Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37966, United States ‡

ABSTRACT: In this work, we investigated SO2 absorption by deep eutectic solvents (DESs) formed by 1-ethyl-3-methylimidazolium chloride (EmimCl) and ethylene glycol (EG) under different conditions. DESs with different molar ratios of EmimCl and EG (from 2:1 to 1:2) were prepared. The results showed that all the EmimCl-EG solvents were very efficient for SO2 capture. It was demonstrated that the SO2 solubility increased with increasing concentrations of EmimCl in DESs. The effects of temperature and SO2 partial pressure were also investigated. The Emim-EG (2:1) solvent could absorb 1.15 (53 wt %) g SO2/ g solvent at 20 °C and 1.0 atm, a much higher capacity than that of other DESs reported to date under the same conditions. Moreover, the SO2 desorption temperature of the solvents could be tuned by changing the composition of the solvents, and all the EmimCl-EG solvents showed excellent reversibility. Nuclear magnetic resonance and Fourier transform infrared spectra showed the interactions of the solvents and SO2. KEYWORDS: Absorption, Deep eutectic solvents, Ethylene glycol, Ionic liquids, Sulfur dioxide

■

INTRODUCTION Sulfur dioxide (SO2), mainly generated from the consumption of fossil fuels, poses great hazards to human health and the environment. At present, flue gas desulfurization (FGD) processes are the primary method used in industry to reduce and control SO2 emissions. One of the most widely used FGD processes is lime/limestone technology.1−3However, the lime/ limestone method has inherent drawbacks, such as the production of large amounts of solid waste (CaSO4) and the impossibility of recycling SO2.4 Therefore, it is important to develop new efficient and reversible methods of capturing SO2. In recent years, ionic liquids (ILs) have been widely studied for the capture and separation of SO25−13 because of their unique properties, such as high thermal stability, negligible vapor pressure, and tunable structure.14−19 Among ILs, etherfunctionalized,20,21 amine-functionalized,11,22,23and azole-based ILs6,24show excellent SO2 absorption capacity because of their multiple interaction sites for SO2. However, the synthesis of these functional ILs involves a tedious set of steps, which is disadvantageous for their application. Recently, deep eutectic solvents (DESs) have received much attention because of their excellent properties, which are comparable to those of ILs.25,26DESs are easily prepared by mixing two or more compounds without using other solvents. Most DESs are liquids at room temperature, mainly because of the formation of intermolecular hydrogen bonds between the components. DESs have been investigated for various uses, including extraction, electrodeposition, and chemical reactions.27−29 They are also studied for SO2 capture. DESs such as choline chloride(ChCl)-glycerol,30,38 ChCl-EG,32 caprolactam−organic acids,39 and betaine (Bet)-EG33systems can © 2017 American Chemical Society

efficiently capture SO2 and have shown good SO2 absorption capacity. These results show DESs have great potential for use in industry to absorb SO2. Herein, we report the absorption of SO2 by DESs formed by EmimCl and EG. EmimCl is a common IL, and EmimCl-EG is easily prepared. The SO2 absorption capacities of EmimCl-EG solvents with different EmimCl-EG molar ratios (from 2:1 to 1:2) at various temperatures and SO2 partial pressures were determined. The results showed that EmimCl-EG can efficiently capture SO2. The capacity of EmimCl-EG (2:1), in particular, for SO2 capture (1.15 g SO2/g solvent) is much higher than that of DESs previously reported in the literature. Moreover, the regeneration temperature of EmimCl-EG eutectic solvents can be tuned by changing the solvent compositions. The interactions of SO2 and DESs were also studied by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR).

■

EXPERIMENTAL SECTION

Materials and Characterizations. 1-Ethyl-3-methylimidazolium chloride (98+ %) was obtained from Alfa Aesar. Ethylene glycol anhydrous (99.8%) and SO2 (≥99.9%) were purchased from SigmaAldrich. All the chemicals were used directly as received. The IR spectra were recorded on a PerkinElmer Frontier FTIR spectrometer with wavenumbers from 650 to 4000 cm−1. The 1H NMR spectra were taken on a Bruker spectrometer (400 MHz) by using CD3CN (1.94 ppm) as the internal reference. The 13C NMR spectra were recorded Received: May 17, 2017 Revised: June 23, 2017 Published: June 25, 2017 6382

DOI: 10.1021/acssuschemeng.7b01554 ACS Sustainable Chem. Eng. 2017, 5, 6382−6386

Letter

ACS Sustainable Chemistry & Engineering at 100.6 MHz by using CD3CN (118.26 ppm) as the internal reference. Synthesis of DESs. DES was prepared simply by stirring a EmimCl and EG mixture at the desired molar ratio at 70 °C until a homogeneous liquid was formed. The liquid was dried under vacuum for 6 h at 70 °C before use. The methods to prepare EmimCl-EG (2:1) are described as follows: EmimCl (2.93g, 20 mmol) was added into a glass vial, and then EG (0.62 g, 10 mmol) was added. The mixture was then heated and stirred at 70 °C until a homogeneous liquid was formed. The methods to prepare EmimCl-EG (1:1) and EmimCl-EG (1:2) were similar to EmimCl-EG (1:1). The difference is just a change in the EmimCl-EG molar ratios. NMR and FTIR Data of DESs. EmimCl-EG (2:1): 1H NMR (CD3CN,400 MHz): δ 8.74 (s, 1H), 7.41(s, 1H), 7.35(s, 1H),4.17(q, 2H), 3,83(s, 3H), 3.51(s, 2H), 1.45(t, 3H) ppm. 13C NMR(CD3CN, 100.6 MHz): δ 137.3,124.3, 122.7, 64.5, 45.5, 36.6, 15.5 ppm. FTIR: 3294, 3145, 3066, 2979, 2941,2866, 1571, 1452,1388, 1334, 1169, 1089,1042,959, 883, 858, 760, 701 cm−1. EmimCl-EG (1:1): 1H NMR (CD3CN,400 MHz): δ 8.66 (s, 1H), 7.40(s, 1H), 7.34(s, 1H),4.17(q, 2H), 3,83(s, 3H), 3.51(s, 4H), 1.45(t, 3H) ppm. 13C NMR(CD3CN, 100.6 MHz): δ 137.2,124.4, 122.7, 64.5, 45.5, 36.6, 15.5 ppm. FTIR: 3305, 3147, 3080, 2979, 2940, 2868, 1571, 1452, 1389, 1334, 1169, 1088, 1040, 959, 883, 859, 758, 701 cm−1. EmimCl-EG (1:2): 1H NMR (CD3CN,400 MHz): δ 8.59 (s, 1H), 7.39(s, 1H), 7.34(s, 1H),4.16(q, 2H), 3,82(s, 3H), 3.50(s, 8H), 1.45(t, 3H) ppm. 13C NMR(CD3CN, 100.6 MHz): δ 137.0,124.4, 122.7, 64.3, 45.5, 36.6, 15.5 ppm. FTIR: 3315, 3147, 3100, 2940, 2870, 1572, 1453, 1389, 1333, 1169, 1087, 1037, 960, 883, 859, 756, 700 cm−1. Absorption and Desorption of SO2. DES (about 1.0 g) was charged into a glass tube with an inner diameter of 10 mm, and the glass tube was immersed in a water or oil bath of the desired temperature. SO2 was bubbled through the solvent in the tube at a flow rate of 50 mL/min. The SO2 absorbed by the solvent was determined at regular intervals during the absorption process by an electronic balance with an accuracy of ±0.1 mg (Mettler Toledo XS204). The method described was also used for the absorption of SO2 under reduced partial pressure. For SO2 absorption at different partial pressures, the SO2 pressure was obtained by controlling the flow rates of SO2 and N2. In the regeneration process, N2 at atmospheric pressure was bubbled through the solutions at the desired temperature [80 °C for EmimCl-EG (2:1) and EmimCl-EG (1:1) and 60 °C for EmimCl-EG (1:2)], with a flow rate of 50 mL/min.

absorption amount increased as the EmimCl concentration increased in DESs. The SO2 solubilities in EmimCl-EG (1:2), EmimCl-EG (1:1), and EmimCl-EG (2:1) are 0.82 g (45 wt %), 1.03 g (51 wt %), and 1.15 g (53 wt %) of SO2 per gram of solvent, respectively. The high SO2 absorption capacity may be due to the strong charge transfer interactions of acidic SO2 and Cl− in EmimCl.9,34,35 There is no obvious color change for the solvents upon SO2 absorption. Compared with the EmimCl-EG solvents, the viscosity of the three DESs decreased obviously after saturation with SO2 at 1.0 atm. Moreover, we also sutdied the SO2 absoprtion capacity of EG at 20 °C and 1.0 atm, and the value was 0.28 g of SO2 per g of EG, which is much lower than that of the EmimCl-EG (2:1) solvent. The results indicate that EmimCl is very important to improve the SO2 absorption capacity of DESs. Figure 2 shows the effect of temperature on SO2 absorption by the solvents at 1.0 atm pressure. As shown in Figure 2, the

Figure 2. Effect of temperature on SO2 absorption by EmimCl-EG at 1.0 atm.

SO2 absorption capacities of the eutectics decreased continuously with increasing temperature. For example, the solubility of SO2 in EmimCl-EG (2:1) decreased from 1.15 to 0.59 g SO2/g solvent when the temperature increased from 20 to 60 °C. These results indicate that most captured SO2 could easily be released by heating the absorption system, and low temperatures are favorable for the solvent to capture SO2. The effects of SO2 partial pressure on the absorption performances of the solvents were also studied because of the low SO2 concentrations in flue gas.6,12 The results are shown in Figure 3. As shown in Figure 3, the SO2 absorption capacity

■

RESULTS AND DISCUSSION In this work, three EmimCl-EG DESs with different EmimClEG molar ratios (from 2:1 to 1:2) were prepared, and their absorption capacities for SO2 at different conditions were determined. Figure 1 presents the time-dependent absorption of SO2 by the solvents at 20 °C and 1.0 atm. As clearly shown, the absorption of SO2 by these eutectics can be completed within 10 min. Moreover, Figure 1 shows that the composition of DESs greatly affects their absorption capacity. The SO2

Figure 3. Effect of SO2 pressure on SO2 absorption by EmimCl-EG at 20 °C.

decreased with decreasing SO2 partial pressure. For example, the SO2 absorption capacity of EmimCl-EG (2:1) decreased from 1.15 to 0.42 g SO2/g solvent as the SO2 pressure decreased from 1.0 to 0.10 atm. The SO2 absorption capacities of the three solvents were compared with those of the typical DESs and ILs reported in the literatures, as shown in Table 1. As shown, EmimCl-EG (2:1) exhibits an extremely high absorption capacity at both 1.0 and 0.10 atm. Note that 1.0 g of Emim-EG (2:1) could absorb

Figure 1. SO2 absorption capacities of EmimCl-EG as a function of time at 20 °C and 1.0 atm. 6383

DOI: 10.1021/acssuschemeng.7b01554 ACS Sustainable Chem. Eng. 2017, 5, 6382−6386

Letter

ACS Sustainable Chemistry & Engineering

behavior of DESs can be tuned. The results indicate more choices for SO2 capture by DESs. Moreover, as shown in Figure 4, no notable change in the SO2 absorption capacity of the solvent was seen during five consecutive absorption− desorption cycles, indicating that the capture of SO2 by EmimCl-EG solvents is highly reversible. FTIR and NMR spectra of the solvent before and after SO2 absorption were analyzed to study the absorption mechanism. The FTIR spectra are shown in Figure 5. Comparing the

Table 1. Comparison of SO2 Absorption Capacities of Different DESs and ILs SO2 absorption (g SO2/g solvent) IL or DES

T (°C)

1.0 atm

0.10 atm

ref

EmimCl-EG (2:1) [Emim][SCN] [NEt2C2Py][SCN] EmimCl-EG (1:1) [E3mim][Tetz] EmimCl-EG (1:2) ChCl-Thiourea (1:1) ChCl-Glycerol (1:1) TEAC-LA (1:3) CPL-KSCN (3:1) ChCl-LA (1:3) ChCl-EG (1:2) [P66614][Tetz] Bet-EG (1:3) L-car-EG (1:3)

20 20 20 20 20 20 30 20 20 20 20 30 20 40 40

1.15 (53%)c 1.13 1.06 1.03 (51%) 0.95 0.82 (45%) 0.70 0.678 0.625 0.607 0.557 0.55 0.43 0.366 0.365

0.42 (30%) 0.37 0.37 0.31 (24%) 0.34 0.22 (18%) 0.09a 0.153 − − 0.124 0.16a 0.18 0.0701b 0.151b

this work 8 23 this work 24 this work 32 30 31 36 31 32 6 33 33

a

Figure 5. FTIR spectra for EmimCl-EG (2:1) before and after capture of SO2.

At 0.20 atm. bAt 0.02 atm. cData in brackets are the mass fraction.

0.42 g of SO2 at 0.10 atm. This could be advantageous because of the low SO2 partial pressure in flue gas, and it is important to improve the SO2 absorption capacities of the solvents at low pressures. To the best of our knowledge, among DESs, EmimCl-EG (2:1) has the highest absorption amount (1.15 g SO2/g solvent) under similar conditions according to what has been reported. The reusability of the solvent is also an important factor for SO2 absorption. We studied the absorption/desorption recycling properties of the solvent in this work. Figure 4

spectra before and after SO2 absorption shows that two typical vibrational frequencies of SO2 appear near 1292 and 1132 cm−1, which are attributed to the asymmetrical (Vas) and symmetrical (Vs) stretching vibration,31,40 respectively. However, these bands are found at 1344 and 1145 cm−1 for SO2 in noncomplexating CCl4.37 We also investigated the FTIR spectra of EG before and after SO2 absorption. The Vas and Vs peaks of SO2 appeared at 1326 and 1148 cm−1 for SO2 in EG, respectively. So, based on the above disscusion, after SO2 is absorbed in the EmimCl-EG solvent, the Vas and Vs peaks of SO2 shift to low frequencies, which may be a result of the charge−transfer interaction of the electropositive sulfur atom of SO2 with Cl− in the solvent.34 In the 1H and 13C NMR spectra (Figure 6), neither obvious chemical shifts nor new peaks are found, suggesting that SO2 interacts physically with EG and the cation of EmimCl. Furthermore, we caculate the absorption enthalpy of SO2 for EmimCl-EG (2:1) based on the experimental data, and the value is −40.6 kJ/mol, which is lower than that of EG (∼ −26.1 kJ/mol).41This is mainly due to the strong charge−transfer interaction of the sulfur atom of SO2 with Cl−, and this result is inconsistent with the FTIR and NMR disccusion.

Figure 4. Five consecutive cycles of SO2 absorption and desorption by the solvents: ■ = EmimCl-EG (2:1), ⧫ = EmimCl-EG (1:1), ▼ = EmimCl-EG (1:2).

illustrates the absorption/desorption processes. Most of the SO2 (about 96%) captured by EmimCl-EG (2:1) can be released at 80 °C within 50 min by bubbling N2 through the solution. For the EmimCl-EG (1:1) system, all the captured SO2 can be released completely at the same condition. The desorption temperature is much lower than that of BmimCl (140 °C).35 Furthermore, all the SO2 captured by EmimCl-EG (1:2) can be desorbed at 60 °C within 50 min, indicating the lower energy cost for SO2 desorption. The desorption behaviors are different mainly because the interaction between EmimCl and SO2 can be reduced at an increasing concentration of EG, which is favorable for the release of SO2. The more EG in the solvent there is, the stronger hydrogen interaction is between EG and EmimCl, which will reduce the interaction between EmimCl and SO2. These results indicate that not only the SO2 absorption capacity but also the SO2 desorption

■

CONCLUSIONS DESs formed by EmimCl and EG absorbed SO2 efficiently. The SO2 absorption capacity of EmimCl-EG DES increased as EmimCl concentration increased in the solvents. The SO2 solubility in the solvents decreased with increasing temperature or decreasing SO2 partial pressure. The Emim-EG (2:1) solvent could absorb 1.15 (53 wt %) g SO2/g solvent at 20 °C and 1.0 atm, a much higher capture rate than that of other DESs reported to date in the literature at the same conditions. Moreover, the desorption temperature could be tuned by changing the DES composition, and EmimCl-EG DES showed excellent reusability. All the results showed that EmimCl-EG DESs are promising absorbents for SO2. 6384

DOI: 10.1021/acssuschemeng.7b01554 ACS Sustainable Chem. Eng. 2017, 5, 6382−6386

Letter

ACS Sustainable Chemistry & Engineering

(6) Wang, C. M.; Cui, G. K.; Luo, X. Y.; Xu, Y. J.; Li, H. R.; Dai, S. Highly Efficient and Reversible SO2 Capture by Tunable Azole-Based Ionic Liquids through Multiple-Site Chemical Absorption. J. Am. Chem. Soc. 2011, 133, 11916−11919. (7) Cui, G.; Zheng, J.; Luo, X.; Lin, W.; Ding, F.; Li, H.; Wang, C. Tuning Anion-Functionalized Ionic Liquids for Improved SO2 Capture. Angew. Chem., Int. Ed. 2013, 52, 10620−10624. (8) Wang, C. M.; Zheng, J. J.; Cui, G. K.; Luo, X. Y.; Guo, Y.; Li, H. R. Highly efficient SO2 capture through tuning the interaction between anion-functionalized ionic liquids and SO2. Chem. Commun. 2013, 49, 1166−1168. (9) Xing, H. B.; Liao, C.; Yang, Q. W.; Veith, G. M.; Guo, B. K.; Sun, X. G.; Ren, Q. L.; Hu, Y. S.; Dai, S. Ambient Lithium-SO2 Batteries with Ionic Liquids as Electrolytes. Angew. Chem., Int. Ed. 2014, 53, 2099−2103. (10) Jin, M. J.; Hou, Y. C.; Wu, W. Z.; Ren, S. H.; Tian, S. D.; Xiao, L.; Lei, Z. G. Solubilities and Thermodynamic Properties of SO2 in Ionic Liquids. J. Phys. Chem. B 2011, 115, 6585−6591. (11) Yang, Z. Z.; He, L. N.; Song, Q. W.; Chen, K. H.; Liu, A. H.; Liu, X. M. Highly efficient SO2 absorption/activation and subsequent utilization by polyethylene glycol-functionalized Lewis basic ionic liquids. Phys. Chem. Chem. Phys. 2012, 14, 15832−15839. (12) Anderson, J. L.; Dixon, J. K.; Maginn, E. J.; Brennecke, J. F. Measurement of SO2 solubility in ionic liquids. J. Phys. Chem. B 2006, 110, 15059−15062. (13) Cui, G. K.; Zhang, F. T.; Zhou, X. Y.; Huang, Y. J.; Xuan, X. P.; Wang, J. J. Acylamido-Based Anion-Functionalized Ionic Liquids for Efficient SO2 Capture through Multiple-Site Interactions. ACS Sustainable Chem. Eng. 2015, 3, 2264−2270. (14) Dzida, M.; Zorębski, E.; Zorębski, M.; Ż arska, M.; GeppertRybczyńska, M.; Chorążewski, M.; Jacquemin, J.; Cibulka, I. Speed of Sound and Ultrasound Absorption in Ionic Liquids. Chem. Rev. 2017, 117, 3883−3929. (15) Nelyubina, Y. V.; Shaplov, A. S.; Lozinskaya, E. I.; Buzin, M. I.; Vygodskii, Y. S. A New Volume-Based Approach for Predicting Thermophysical Behavior of Ionic Liquids and Ionic Liquid Crystals. J. Am. Chem. Soc. 2016, 138, 10076−10079. (16) Greaves, T. L.; Drummond, C. J. Protic Ionic Liquids: Evolving Structure-Property Relationships and Expanding Applications. Chem. Rev. 2015, 115, 11379−11448. (17) Hayes, R.; Warr, G. G.; Atkin, R. Structure and Nanostructure in Ionic Liquids. Chem. Rev. 2015, 115, 6357−6426. (18) Cui, G.; Wang, J.; Zhang, S. Active chemisorption sites in functionalized ionic liquids for carbon capture. Chem. Soc. Rev. 2016, 45, 4307−4339. (19) Ho, T. D.; Zhang, C.; Hantao, L. W.; Anderson, J. L. Ionic Liquids in Analytical Chemistry: Fundamentals, Advances, and Perspectives. Anal. Chem. 2014, 86, 262−285. (20) Zhang, L. H.; Zhang, Z. J.; Sun, Y. L.; Jiang, B.; Li, X. G.; Ge, X. H.; Wang, J. T. Ether-Functionalized Ionic Liquids with Low Viscosity for Efficient SO2 Capture. Ind. Eng. Chem. Res. 2013, 52, 16335− 16340. (21) Hong, S. Y.; Im, J.; Palgunadi, J.; Lee, S. D.; Lee, J. S.; Kim, H. S.; Cheong, M.; Jung, K. D. Ether-functionalized ionic liquids as highly efficient SO2 absorbents. Energy Environ. Sci. 2011, 4, 1802−1806. (22) Yang, D. Z.; Hou, M. Q.; Ning, H.; Ma, J.; Kang, X. C.; Zhang, J. L.; Han, B. X. Reversible Capture of SO2 through Functionalized Ionic Liquids. ChemSusChem 2013, 6, 1191−1195. (23) Zeng, S. J.; He, H. Y.; Gao, H. S.; Zhang, X. P.; Wang, J.; Huang, Y.; Zhang, S. J. Improving SO2 capture by tuning functional groups on the cation of pyridinium- based ionic liquids. RSC Adv. 2015, 5, 2470− 2478. (24) Cui, G. K.; Wang, C. M.; Zheng, J. J.; Guo, Y.; Luo, X. Y.; Li, H. R. Highly efficient SO2 capture by dual functionalized ionic liquids through a combination of chemical and physical absorption. Chem. Commun. 2012, 48, 2633−2635. (25) Zhang, Q. H.; De Oliveira Vigier, K.; Royer, S.; Jerome, F. Deep eutectic solvents: syntheses, properties and applications. Chem. Soc. Rev. 2012, 41, 7108−7146.

Figure 6. 1H NMR (a) and 13C NMR (b) of EmimCl-EG (2:1) before and after capture of SO2.

■

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (D. Yang). *E-mail: [email protected] (S. Dai). ORCID

Dezhong Yang: 0000-0003-4490-3423 Sheng Dai: 0000-0002-8046-3931 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was supported financially by the National Natural Science Foundation of China (No. 21503196) and the Fundamental Research Funds of the Central Universities (No. 2652015192). S. Dai was supported by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, US Department of Energy.

■

REFERENCES

(1) Wu, H.; Pan, D.; Huang, R.; Hong, G.; Yang, B.; Peng, Z.; Yang, L. Abatement of Fine Particle Emission by Heterogeneous Vapor Condensation During Wet Limestone-Gypsum Flue Gas Desulfurization. Energy Fuels 2016, 30, 6103−6109. (2) Córdoba, P. Status of Flue Gas Desulphurisation (FGD) systems from coal-fired power plants: Overview of the physic-chemical control processes of wet limestone FGDs. Fuel 2015, 144, 274−286. (3) Shannon, M. S.; Irvin, A. C.; Liu, H. N.; Moon, J. D.; Hindman, M. S.; Turner, C. H.; Bara, J. E. Chemical and Physical Absorption of SO2 by N-Functionalized Imidazoles: Experimental Results and Molecular-level Insight. Ind. Eng. Chem. Res. 2015, 54, 462−471. (4) Srivastava, R. K.; Jozewicz, W. Flue gas desulfurization: The state of the art. J. Air Waste Manage. Assoc. 2001, 51, 1676−1688. (5) Wu, W. Z.; Han, B. X.; Gao, H. X.; Liu, Z. M.; Jiang, T.; Huang, J. Desulfurization of flue gas: SO2 absorption by an ionic liquid. Angew. Chem., Int. Ed. 2004, 43, 2415−2417. 6385

DOI: 10.1021/acssuschemeng.7b01554 ACS Sustainable Chem. Eng. 2017, 5, 6382−6386

Letter

ACS Sustainable Chemistry & Engineering (26) Paiva, A.; Craveiro, R.; Aroso, I.; Martins, M.; Reis, R. L.; Duarte, A. R. C. Natural Deep Eutectic Solvents - Solvents for the 21st Century. ACS Sustainable Chem. Eng. 2014, 2, 1063−1071. (27) Smith, E. L.; Abbott, A. P.; Ryder, K. S. Deep Eutectic Solvents (DESs) and Their Applications. Chem. Rev. 2014, 114, 11060−11082. (28) Wagle, D. V.; Zhao, H.; Baker, G. A. Deep Eutectic Solvents: Sustainable Media for Nanoscale and Functional Materials. Acc. Chem. Res. 2014, 47, 2299−2308. (29) Garcia, G.; Aparicio, S.; Ullah, R.; Atilhan, M. Deep Eutectic Solvents: Physicochemical Properties and Gas Separation Applications. Energy Fuels 2015, 29, 2616−2644. (30) Yang, D. Z.; Hou, M. Q.; Ning, H.; Zhang, J. L.; Ma, J.; Yang, G. Y.; Han, B. X. Efficient SO2 absorption by renewable choline chlorideglycerol deep eutectic solvents. Green Chem. 2013, 15, 2261−2265. (31) Deng, D. S.; Han, G. Q.; Jiang, Y. T. Investigation of a deep eutectic solvent formed by levulinic acid with quaternary ammonium salt as an efficient SO2 absorbent. New J. Chem. 2015, 39, 8158−8164. (32) Sun, S. Y.; Niu, Y. X.; Xu, Q.; Sun, Z. C.; Wei, X. H. Efficient SO2 Absorptions by Four Kinds of Deep Eutectic Solvents Based on Choline Chloride. Ind. Eng. Chem. Res. 2015, 54, 8019−8024. (33) Zhang, K.; Ren, S. H.; Hou, Y. C.; Wu, W. Z. Efficient absorption of SO2 with low-partial pressures by environmentally benign functional deep eutectic solvents. J. Hazard. Mater. 2017, 324, 457−463. (34) Ando, R. A.; Siqueira, L. J. A.; Bazito, F. C.; Torresi, R. M.; Santos, P. S. The sulfur dioxide-1-butyl-3-methylimidazolium bromide interaction: Drastic changes in structural and physical properties. J. Phys. Chem. B 2007, 111, 8717−8719. (35) Lee, K. Y.; Kim, C. S.; Kim, H.; Cheong, M.; Mukherjee, D. K.; Jung, K. D. Effects of Halide Anions to Absorb SO2 in Ionic Liquids. Bull. Korean Chem. Soc. 2010, 31, 1937−1940. (36) Liu, B. Y.; Wei, F. X.; Zhao, J. J.; Wang, Y. Y. Characterization of amide-thiocyanates eutectic ionic liquids and their application in SO2 absorption. RSC Adv. 2013, 3, 2470−2476. (37) vanDam, M. H. H.; Lamine, A. S.; Roizard, D.; Lochon, P.; Roizard, C. Selective sulfur dioxide removal using organic solvents. Ind. Eng. Chem. Res. 1997, 36, 4628−4637. (38) Li, H. P.; Chang, Y. H.; Zhu, W. S.; Wang, C. W.; Wang, C.; Yin, S.; Zhang, M.; Li, H. M. Theoretical evidence of charge transfer interaction between SO2 and deep eutectic solvents formed by choline chloride and glycerol. Phys. Chem. Chem. Phys. 2015, 17, 28729− 28742. (39) Liu, B.; Zhao, J.; Wei, F. Characterization of caprolactam based eutectic ionic liquids and their application in SO2 absorption. J. Mol. Liq. 2013, 180, 19−25. (40) Yang, Z. Z.; He, L. N.; Zhao, Y. N.; Yu, B. Highly efficient SO2 absorption and its subsequent utilization by weak base/polyethylene glycol binary system. Environ. Sci. Technol. 2013, 47, 1598−1605. (41) Huang, K.; Xia, S.; Zhang, X. M.; Chen, Y. L.; Wu, Y. T.; Hu, X. B. Comparative study of the solubilities of SO2 in five low volatile organic solvents (sulfolane, ethylene glycol, propylene carbonate, Nmethylimidazole, and N-methylpyrrolidone). J. Chem. Eng. Data 2014, 59, 1202−1212.

6386

DOI: 10.1021/acssuschemeng.7b01554 ACS Sustainable Chem. Eng. 2017, 5, 6382−6386