Ionic liquids in gas separation processing

Ionic liquids in gas separation processing

Available online at www.sciencedirect.com ScienceDirect Current Opinion in Green and Sustainable Chemistry Ionic liquids in gas separation process...

735KB Sizes 0 Downloads 88 Views

Available online at www.sciencedirect.com

ScienceDirect

Current Opinion in

Green and Sustainable Chemistry

Ionic liquids in gas separation processing Dawei Shanga,b, Xinyan Liua, Lu Baia, Shaojuan Zenga, Qiuxia Xua,c, Hongshuai Gaoa and Xiangping Zhanga Ionic liquids (ILs) are recognized as novel solvents for both acid and base gases separations in industrial processes to solve the possible problems caused by the traditional organic solvent methods, such as high energy consumption and second pollutions. In this paper, the absorption performance and absorption mechanism of several typical gases, including CO2, SO2, H2S and NH3, in conventional and functionalized ILs are briefly summarized and discussed. Besides, the method of screening ILs with COSMOS-RS, and the process simulation, assessment and design for new IL-based gas separation processes are also reviewed. Addresses a Key Laboratory of Green Process and Engineering, State Key Laboratory of Multiphase Complex System, Beijing Key Laboratory of Ionic Liquids Clean Process, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100190, China b College of Chemical and Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China c School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China Corresponding author: Zhang, Xiangping ([email protected])

Current Opinion in Green and Sustainable Chemistry 2017, 5:74–81 This review comes from a themed issue on Green Solvents 2017 Edited by Charlotta Turner and Jianji Wang http://dx.doi.org/10.1016/j.cogsc.2017.03.015

separation technologies is an enduring R&D topic, and the key is to design new solvents or materials and then the corresponding novel processes. In recent years, ionic liquids (ILs) have emerged as a promising option for gas separations [6], which are entirely composed of cations and anions. Compared with traditional solvents, their desirable properties, such as negligible vapor pressures, high thermal stability and tunable structures, endow ILs the advantages of lower energy consumption, less loss of absorbents, no waste water discharge and so on [7]. The visual comparison of CO2 absorption by monoethanolamine (MEA) aqueous solution and 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) is as shown in Figure 1. The undesired industrial gases considered in this paper are mainly divided into acid gases and base gases, i.e., CO2, SO2, H2S and NH3. Research on such gases absorption by both conventional and functionalized ILs and the absorption mechanism, absorbents screening method with COSMO-RS, and process simulation for gas separation are also reviewed.

Absorption performance and mechanism of gases in ionic liquids CO2 solubility in ionic liquids and the absorption mechanism Physical absorption

The rapid development of human civilization during recent centuries is based on the energy and environment and at present, environmental degradation has become one of the main impediments for further progress of the society. For example, a large sum of undesired gases emitted from industries cause global warming [1,2], acid rain [3], fog and haze [4,5], which have severely threatened the living environment of human beings. Gas separation is an important operation unit to treat the industrial tail gases or process gases and there are already many technologies for gas separations, like physical or chemical solvents scrubbing, pressure swing absorption (PSA) and gas membrane separation. However, due to the complexity of the gas components and diverse conditions, most technologies still suffer from high energy consumption, high cost and secondary pollutions. Thus, developing new gas

The most common way in industries to capture CO2 is the absorption by organic amine solutions, such as MEA [8e10] and methyldiethanolamine/piperazine (MDEA/ PZ) aqueous solutions [11,12]. However, the drawbacks including pipeline corrosion, absorbent degradation and high energy consumption limit the applications of these methods. In order to solve the problem, many new absorbents have been developed [13] and among them, ILs are a promising option. In 1999, Blanchard et al. [14] first absorption by 1-butyl-3reported CO2 methylimidazolium hexafluorophosphate ([Bmim] [PF6]) and found the high solubility of CO2 in IL but insolubility of IL in CO2. Since then research on conventional and functionalized ILs for CO2 capture received great attentions. For traditional ILs, the interactions between CO2 and ILs are mainly composed of electrostatic, Van der Waals and hydrogen-bonding forces [15e19]. Therefore, the solubility of CO2 in such ILs is related to the structures of cations and anions. Aki et al. [20] measured CO2 solubility in ILs with different length of the cations’ alkyl chain and demonstrated that the longer the length of alkyl chain, the higher the CO2

Current Opinion in Green and Sustainable Chemistry 2017, 5:74–81

www.sciencedirect.com

2452-2236/© 2017 Elsevier B.V. All rights reserved.

Introduction

Ionic liquids in gas separation processing Shang et al.

75

Figure 1

CO2 absorption by MEA aqueous solution (a) and [Bmim][BF4] (b).

solubility. Anthony et al. [21] designed a few cations paired with different anions and found that the effect of anions on the CO2 solubility is much larger than the cations, which was also confirmed by other researchers [22,23]. Chemical absorption

Op]) could absorb 1.58 mol CO2/mol IL under ambient conditions and the probable absorption mechanism was as shown in Figure 2. SO2 solubility in ionic liquids and the absorption mechanism Physical absorption

In order to achieve higher CO2 absorption capacity to compete with conventional amine solutions, functionalized ILs by introducing amino or other groups onto cation or anion are developed and the higher CO2 absorption capacity is attributed to the chemical interactions between ILs and CO2 [24e36]. The first aminofunctionalized IL 1-butyl-3-propylamineimidazolium tetrafluoroborate ([NH2p-bim][BF4]) using for CO2 capture was reported by Bates et al. [24] and the molar ratio of CO2/IL was about 0.5 at 295 K, 100 kPa. The possible absorption mechanism was the reaction between CO2 and the amino group and then carbamate was formed. In addition to append amino on the cation, researchers also designed ILs with amino-functionalized anions and the ILs could even achieve equimolar absorption of CO2 [26,27]. Zhang et al. [37] synthesized a kind of dual amino-functionalized cation-tethered IL and the CO2 gravimetric capacity of the IL reached up to 18.5 wt %. However, not all NH2-functionalzied ILs can achieve such high CO2 absorption capacity for the reason that the HOMO and LUMO energies for CO2 and various NH2-functionalzied ILs were different [25,38]. For the sake of overcoming the high viscosities and complex synthesis of these amino-functionalized ILs, Wang et al. [30,32,33,35] developed a series of nonamino ILs to capture CO2, such as super base-derived protic ILs and diverse phenolic ILs with multi-active sites on anions. The results showed that trihexyl (tetradecyl)phosphonium 2- hydroxypyridinate ([P66614][2-

Another typical acid gas is SO2, often existing in flue gases emitted from power plants. In the past decades, design and synthesis of various ILs as efficient absorbents for SO2 absorption and separation offer a new opportunity for developing novel separation processes that are capable of reversibly capturing SO2 with a high capacity and low absorption enthalpy [3,39e49]. The relationship between the structures and the absorption performance of the conventional ILs had been clarified by many researchers [3,50]. Zeng et al. [51] systematically investigated the effect of the alkyl chain length of cations and various anions on SO2 solubility in ILs. The results revealed that the length of the alkyl chain had a minor influence on SO2 absorption performance, while anions played a dominant role in SO2 absorption. Moreover, the surprisingly high absorption capacity of SO2 in N-butylpyridinium thiocyanate ([C4Py][SCN]) was mostly attributed to the stronger electrostatic interaction between the anion and SO2. Ether and nitrile-functionalized ILs also displayed excellent capacity for SO2 capture and the enhanced absorption is due to the stronger physical interaction between ILs and SO2 in comparison with non-functionalized analogs [C4Py][SCN] [52,53].

www.sciencedirect.com

Current Opinion in Green and Sustainable Chemistry 2017, 5:74–81

Chemical absorption

Wu et al. [54] first reported TMG-based IL (1,1,3,3tetramethylguanidinium lactate, [TMG][L]) for SO2 absorption through physical and chemical interactions and

76 Green Solvents 2017

Figure 2

The plausible mechanism of CO2 absorption by [P66614][2-Op] through multiple-site cooperative interactions [35] (Reproduced with permission from Ref. [35]. Copyright 2014WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).

the IL can efficiently absorb SO2 with high capacity under both ambient and low partial pressures. Further explanation about the interactions between SO2 and TMG-based ILs combining experiments, molecular dynamic simulation and ab-initio calculation were conducted by other researchers [50,55,56]. On the basis of this, Wu et al. [56] proposed a new method to distinguish the functionalized ILs and non-functionalized ILs according to the pKa values of the acids forming the ILs. Subsequently, azole and phenolate-based ILs were developed to further improve SO2 capacity through multiple-site interactions and the SO2 solubility was up to 5.7 mol SO2/mol IL with tunable absorption enthalpy [42,46,47,57,58]. Interestingly, Zeng et al. [59] revealed the unusual viscosity changes of 1-(2-diethylaminoethyl)pyridinium thiocyanate ([NEt2C2Py][SCN]) during SO2 absorption owing to different absorption stages of chemical and physical interaction respectively, as shown in Figure 3.

H2S solubility in ionic liquids and the absorption mechanism

Natural gas and biogas often contain the poisonous acid gas H2S, which should be removed before utilization. The traditional amine aqueous solutions for natural gas sweetening suffer from many impediments [60]. Therefore, ILs are introduced to remove H2S from these gases. Pomelli et al. [61] studied the solubility of H2S in a series of imidazolium-based cation ILs with different anions and as expected, the cation has a moderate effect on the H2S solubility and strong hydrogen bonds formed between H2S and the anions, which is confirmed by Aparicio et al. [62] and Sakhaeinia et al. [63]. Dual Lewis base functionalized ILs were reported by Huang et al. for the selective absorption of H2S and the solubility reached 0.84 mol H2S/mol IL at 333 K, 100 kPa, attributing to the formation of the N/H/S hydrogen bond [64]. Ma et al. [65] studied the chemical reaction between 1.6

Figure 3

The viscosity of pyridinium-based ILs with SO2 absorption capacity [59] (Reproduced with permission from Ref. [59]. Copyright 2015 American Chemical Society). Current Opinion in Green and Sustainable Chemistry 2017, 5:74–81

www.sciencedirect.com

Ionic liquids in gas separation processing Shang et al.

[Et3NHCl]$[FeCl3] (triethylamine hydrochloride blending with ferric chloride, molar rate 1.6:1) and H2S and the solubility was up to 6.36 g/L in the Fe-based ILs. Huang et al. [66,67] further researched the selective absorption of H2S over CO2 with hydrophobic protic ionic liquids and substituted benzoate-based ILs, and the H2S/ CO2 selectivity was up to 37.2 at 298 K, 100 kPa. Also, Huang et al. [68] used ILs to serve as the efficient media for the Claus reaction of SO2 and H2S and 1-hexyl-3methylimidazolium chloride ([Hmim][Cl]) enabled the transformation of H2S to S8 with a conversion ratio as high as > 96% within 3 min. NH3 solubility in ionic liquids and the absorption mechanism

Direct emission of NH3 from chemical industries heavily pollutes the environment and the water scrubbing method is one of the main methods to treat the exhausted gases. Compared with water or acid scrubbing methods, ILs serving as NH3 absorbents have showed great advantages, such as no waste water discharge and recovery of pure NH3 product. Yokozeki et al. [69,70] first reported 8 kinds of ILs for NH3 absorption at ranges of temperatures and pressures and they concluded intermolecular complex interactions might form between NH3 and ILs. Shi et al. [71] declared that NH3 interacted more strongly with cations than the anions, which was in contrast to the situation of CO2 absorption by ILs. The further work about the influence of the length of the cation’s alkyl chain on the NH3 solubility was studied by Li et al. [72]. Systematically, Palomar et al. [73,74] screened 272 kinds of ILs and ultimately hydroxyl-functionalized ILs, 1e2 (-Hydroxyethyl)-3-methylimidazolium tetrafluoroborate and cholinium bis(tri([EtOHmim][BF4]) fluoromethylsulfonyl)imide ([choline][NTf2]), were selected to absorb NH3 and achieved high solubility. Li et al. [75] found the strong hydrogen bond interaction between NH3 and the H atom of the hydroxyl group, which resulted in the high NH3 absorption. Our group proposed protic ionic liquid 1-butyl imidazolium bis(trifluoromethylsulfonyl)imide ([Bim][NTf2]) with strong hydrogen bond donating ability for NH3 absorption and

77

solubility is up to 2.69 mol NH3/mol IL at 313 K, 100 kPa and the possible absorption mechanism was as shown in Figure 4 [76].

COSMO-RS for ionic liquids screening Apart from the synthesis of ILs, measurements of properties and solubility as well as understanding the absorption mechanism by experimental characteristics are also important. Thus another aspect in this area is to screen and design new ILs according to the thermodynamic model combining with process simulation method. UNIFAC [77], UNIQUAC and EOS models [78] are the traditional methods for predicting the thermodynamic properties of vapor-liquid systems and new methods have been developed. Compared with COSMO, COSMO-RS goes far beyond simple continuum solvation models (CSMs) because of the integrated concepts from quantum chemistry, dielectric continuum models, electrostatic surface interactions and statistical thermodynamics [79,80]. Since COSMO-RS is independent of experimental data and an alternative to structure interpolating group contribution methods, it has been widely used for a quick solvent screening or property predictions. Zhang et al. [81] used the COSMO-RS model to screen ILs for CO2 capture and obtained the Henry’s constants of CO2 in 408 ILs. They found that the ILs with anion [FEP] showed relative higher CO2 absorption capability than other ILs, while Maiti et al. [82] reported that the ILs with all guanidinium-functionalized cations and [BF4] anion possessed a higher CO2 solubility. Marco et al. [83] developed a simple model to predict the solubility of CO2 by combining COSMO-RS for unsymmetrical activity coefficient with PR EOS for calculation of CO2 fugacity coefficient. They found that the molecular mass of ILs has a great effect on Henry’s constant of CO2. Palomar et al. [73,74] performed quantumchemical COSMO-RS analysis to analyze NH3-solvent interactions and then a rational screening of Henry’s coefficient of NH3 over 272 ILs was done to select potential high solvents for NH3 capture. Based on the COSMO-RS model, Liu et al. [84] established a more

Figure 4

Possible NH3 absorption mechanism by [Bim][NTf2] [76] (Reproduced with permission from Ref. [76]. Copyright 2016, Royal Society of Chemistry). www.sciencedirect.com

Current Opinion in Green and Sustainable Chemistry 2017, 5:74–81

78 Green Solvents 2017

comprehensive and systematic method for the screening of ILs. Not only CO2 solubility and CO2/CH4 selectivity, but also the properties of viscosity and toxicity were taken into consideration. Further, a new CO2 capture process with the screened IL was developed and the energy consumption of the process was evaluated. The results showed that the IL-based process can realize energy-saving and environmental friendly target for carbon capture. Similarly, COSMO-RS models are also useful for other gases separation processes [85,86].

Simulation and assessment of ionic liquidsbased gas separation process The screening of appropriate ILs including experimental and COSMO-RS methods is the fundamental work for gas separations, but process simulation and assessment are also an indispensable step for industrial design. However, the thermodynamic properties of ILs are absent and these data are very necessary not only in process simulations but also in the assessment of a new technology. Huang et al. [87] developed a new fragment contribution-corresponding states (FC-CS) method to predict critical properties of ILs and the predicted results agreed well with the experimental data. Based on this reliable thermodynamic model, three ILs blending with MEA for CO2 capture processes were simulated and the CO2 capture cost of the IL-based process was evaluated [88]. Compared with the MEA process, the [C4Py] [BF4]-MEA process was regarded as energy-saving and cost-efficient carbon capture process and other researchers have also obtained the similar conclusions [89e 91]. Xu et al. [92] established process simulation for biogas upgrading and they found the energy consumption and green degree of the IL scrubbing process were respectively the lowest and highest among the three technologies studied. On the basis of COSMO-based process simulations, Ruiz et al. [93] evaluated NH3 absorption refrigeration cycles with ILs as absorbents and the ILs method provided the best cycle’s performance.

adsorption materials. These hybrid materials can keep the excellent features of both ILs and porous materials and meanwhile avoid the possible drawbacks of the pure ILs and traditional porous materials. For example immobilization of ILs in membranes has been extensively investigated to combine the advantages of membranes and ILs [94,95]. Metal organic frameworks (MOF), as an important kind of adsorption materials, have great potential as new porous materials for gas separations, which could be functionalized by ILs to create more adsorption sites for gas molecules and increase the gas selectivity of materials [96,97].

Acknowledgement This work was financially supported by the National Natural Science Fund for Distinguished Young Scholars (21425625), the National Natural Science Foundation of China (51574215, 21606233).

References Papers of particular interest, published within the period of review, have been highlighted as: * of special interest 1.

Figueroa JD, Fout T, Plasynski S, McIlvried H, Srivastava RD: Advances in CO2 capture technology—the U.S. Department of Energy’s Carbon Sequestration Program. Int. J. Greenh. Gas Control 2008, 2:9–20.

2.

Pipitone G, Bolland O: Power generation with CO2 capture: technology for CO2 purification. Int. J. Greenh. Gas Control 2009, 3:528–534.

3.

Anderson JL, Dixon JK, Maginn EJ, Brennecke JF: Measurement of SO2 solubility in ionic liquids. J. Phys. Chem. B 2006, 110: 15059–15062.

4.

Erisman JW, Bleeker A, Galloway J, Sutton MS: Reduced nitrogen in ecology and the environment. Environ. Pollut. 2007, 150:140–149.

5.

Wang G, Zhang R, Gomez ME, Yang L, Levy Zamora M, Hu M, Lin Y, Peng J, Guo S, Meng J, Li J, Cheng C, Hu T, Ren Y, Wang Y, Gao J, Cao J, An Z, Zhou W, Li G, Wang J, Tian P, Marrero-Ortiz W, Secrest J, Du Z, Zheng J, Shang D, Zeng L, Shao M, Wang W, Huang Y, Wang Y, Zhu Y, Li Y, Hu J, Pan B, Cai L, Cheng Y, Ji Y, Zhang F, Rosenfeld D, Liss PS, Duce RA, Kolb CE, Molina MJ: Persistent sulfate formation from London Fog to Chinese haze. Proc. Natl. Acad. Sci. U. S. A. 2016, 113: 13630–13635. http://www.pnas.org/content/113/48/13630.

6.

Lei Z, Dai C, Chen B: Gas solubility in ionic liquids. Chem. Rev. 2014, 114:1289–1326. http://pubs.acs.org/doi/abs/10.1021/ cr300497a.

7.

Zhang X, Zhang X, Dong H, Zhao Z, Zhang S, Huang Y: Carbon capture with ionic liquids: overview and progress. Energy Environ. Sci. 2012, 5:6668–6681.

8.

Budzianowski WM: Single solvents, solvent blends, and advanced solvent systems in CO2 capture by absorption: a review. Int. J. Glob. Warm. 2015, 7:184–225.

9.

Dutcher B, Fan M, Russell AG: Amine-based CO2 capture technology development from the beginning of 2013-a review. ACS Appl. Mater. Interfaces 2015, 7:2137–2148.

Conclusions The absorption of various undesired gases with ILs has displayed potential industrial applications, but there are still many challenges, such as how to design new ILs for better gas absorption performance and overcome the high price and reduce the viscosities of ILs. As mentioned above, it is suggested to screen ILs from the point of molecular simulation and then clarify the interactions of cationeanion, cation-gas and anion-gas and that would be very helpful and efficient. At present stage, blending ILs with organic solvents is a compromising but reasonable method to be applied into the gas separation process in order to reduce the viscosity and cost and however, the drawbacks of organic solvents cannot be totally avoided. In addition, new materials introducing ILs have become promising options for gas separations yet, including the IL-based membranes and Current Opinion in Green and Sustainable Chemistry 2017, 5:74–81

10. Wang T, Hovland J, Jens KJ: Amine reclaiming technologies in post-combustion carbon dioxide capture. J. Environ. Sci. China 2015, 27:276–289. 11. Wang M, Lawal A, Stephenson P, Sidders J, Ramshaw C: Postcombustion CO2 capture with chemical absorption: a stateof-the-art review. Chem. Eng. Res. Des. 2011, 89:1609–1624. 12. Yu CH, Huang CH, Tan CS: A review of CO2 capture by absorption and adsorption. Aerosol Air Qual. Res. 2012, 12: 745–769. www.sciencedirect.com

Ionic liquids in gas separation processing Shang et al.

79

13. MacDowell N, Florin N, Buchard A, Hallett J, Galindo A, Jackson G, Adjiman CS, Williams CK, Shah N, Fennell P: An overview of CO2 capture technologies. Energy Environ. Sci. 2010, 3:1645–1669.

33. Wang CM, Luo HM, Li HR, Zhu X, Yu B, Dai S: Tuning the physicochemical properties of diverse phenolic ionic liquids for equimolar CO2 capture by the substituent on the anion. Chem. Eur. J. 2012, 18:2153–2160.

14. Blanchard LA, Hancu D, Beckman EJ, Brennecke JF: Green processing using ionic liquids and CO2. Nature 1999, 399: 28–29.

34. Luo XY, Ding F, Lin WJ, Qi YQ, Li HR, Wang CM: Efficient and * energy-saving CO2 capture through the entropic effect induced by the intermolecular hydrogen bonding in anion-functionalized ionic liquids. J. Phys. Chem. Lett. 2014, 5:381–386. A strategy for improving CO2 capture by new anion-functionalized ionic liquids (ILs) making use of multiple site cooperative interactions is reported and the CO2 capacity was up to 1.60 mol CO2 per mol IL owing to the p-electron delocalization in the pyridine ring.

15. Kazarian SG, Briscoe BJ, Welton T: Combining ionic liquids and supercritical fluids: in situ ATR-IR study of CO2 dissolved in two ionic liquids at high pressures. Chem. Commun. 2000:2047–2048. 16. Dong K, Zhang S, Wang D, Yao X: Hydrogen bonds in imidazolium ionic liquids. J. Phys. Chem. A 2006, 110:9775–9782. 17. Crowhurst L, Mawdsley PR, Perez-Arlandis JM, Salter PA, Welton T: Solvent-solute interactions in ionic liquids. Phys. Chem. Chem. Phys. 2003, 5:2790–2794. 18. Cadena C, Anthony JL, Shah JK, Morrow TI, Brennecke JF, Maginn EJ: Why is CO2 so soluble in imidazolium-based ionic liquids? J. Am. Chem. Soc. 2004, 126:5300–5308. 19. Huang XH, Margulis CJ, Li YH, Berne BJ: Why is the partial molar volume of CO2 so small when dissolved in a room temperature ionic liquid? Structure and dynamics of CO2 dissolved in BmimPF6. J. Am. Chem. Soc. 2005, 127: 17842–17851. 20. Aki S, Mellein BR, Saurer EM, Brennecke JF: High-pressure phase behavior of carbon dioxide with imidazolium-based ionic liquids. J. Phys. Chem. B 2004, 108:20355–20365. 21. Anthony JL, Anderson JL, Maginn EJ, Brennecke JF: Anion effects on gas solubility in ionic liquids. J. Phys. Chem. B 2005, 109:6366–6374. 22. Bhargava BL, Balasubramanian S: Probing anion-carbon dioxide interactions in room temperature ionic liquids: gas phase cluster calculations. Chem. Phys. Lett. 2007, 444:242–246. 23. Seki T, Grunwaldt J-D, Baiker A: In situ attenuated total reflection infrared spectroscopy of imidazolium-based roomtemperature ionic liquids under “supercritical” CO2. J. Phys. Chem. B 2009, 113:114–122. 24. Bates ED, Mayton RD, Ntai I, Davis JH: CO2 capture by a taskspecific ionic liquid. J. Am. Chem. Soc. 2002, 124:926–927. 25. Yu GR, Zhang SJ, Zhou GH, Liu XM, Chen XC: Structure, interaction and property of amino-functionalized imidazolium ILs by molecular dynamics simulation and ab initio calculation. AIChE J. 2007, 53:3210–3221. 26. Gurkan BE, de la Fuente JC, Mindrup EM, Ficke LE, Goodrich BF, Price EA, Schneider WF, Brennecke JF: Equimolar CO2 absorption by anion-functionalized ionic liquids. J. Am. Chem. Soc. 2010, 132:2116–2117. 27. Goodrich BF, de la Fuente JC, Gurkan BE, Zadigian DJ, Price EA, Huang Y, Brennecke JF: Experimental measurements of amine-functionalized anion-tethered ionic liquids with carbon dioxide. Ind. Eng. Chem. Res. 2011, 50:111–118. 28. Zhang Y, Zhang S, Lu X, Zhou Q, Fan W, Zhang X: Dual aminofunctionalised phosphonium ionic liquids for CO2 capture. Chem. Eur. J. 2009, 15:3003–3011. 29. Xue Z, Zhang Z, Han J, Chen Y, Mu T: Carbon dioxide capture by a dual amino ionic liquid with amino-functionalized imidazolium cation and taurine anion. Int. J. Greenh. Gas Control 2011, 5:628–633. 30. Wang CM, Luo HM, Jiang DE, Li HR, Dai S: Carbon dioxide capture by superbase-derived protic ionic liquids. Angew. Chem. Int. Ed. 2010, 49:5978–5981. 31. Wang CM, Luo HM, Luo XY, Li HR, Dai S: Equimolar CO2 capture by imidazolium-based ionic liquids and superbase systems. Green Chem. 2010, 12:2019–2023. 32. Wang CM, Mahurin SM, Luo HM, Baker GA, Li HR, Dai S: Reversible and robust CO2 capture by equimolar taskspecific ionic liquid-superbase mixtures. Green Chem. 2010, 12:870–874.

www.sciencedirect.com

35. Luo XY, Guo Y, Ding F, Zhao HQ, Cui GK, Li HR, Wang CM: Significant improvements in CO2 capture by pyridinecontaining anion-functionalized ionic liquids through multiple-site cooperative interactions. Angew. Chem. Int. Ed. 2014, 53:7053–7057. 36. Ding F, He X, Luo X, Lin W, Chen K, Li H, Wang C: Highly efficient CO2 capture by carbonyl-containing ionic liquids through Lewis acid-base and cooperative C-HO hydrogen bonding interaction strengthened by the anion. Chem. Commun. 2014, 50:15041–15044. http://pubs.rsc.org/en/Content/ ArticleLanding/2014/CC/C4CC06944G#!divAbstract. 37. Zhang J, Jia C, Dong H, Wang J, Zhang X, Zhang S: A novel dual amino-functionalized cation-tethered ionic liquid for CO2 capture. Ind. Eng. Chem. Res. 2013, 52:5835–5841. 38. Zhang SJ, Yuan XL, Chen YH, Zhang XP: Solubilities of CO2 in 1-butyl-3-methylimidazolium hexafluorophosphate and 1,1,3,3-tetramethylguanidium lactate at elevated pressures. J. Chem. Eng. Data 2005, 50:1582–1585. 39. Lin H, Bai P, Guo X: Ionic liquids for SO2 capture: development and progress. Asian J. Chem. 2014, 26:2501–2506. 40. Huang K, Chen Y-L, Zhang X-M, Xia S, Wu Y-T, Hu X-B: SO2 absorption in acid salt ionic liquids/sulfolane binary mixtures: experimental study and thermodynamic analysis. Chem. Eng. J. 2014, 237:478–486. 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, N-methylimidazole, and N-methylpyrrolidone). J. Chem. Eng. Data 2014, 59:1202–1212. 42. Cui G, Lin W, Ding F, Luo X, He X, Li H, Wang C: Highly efficient SO2 capture by phenyl-containing azole-based ionic liquids through multiple-site interactions. Green Chem. 2014, 16:1211. 43. Lee KY, Kim HS, Kim CS, Jung K-D: Behaviors of SO2 absorption in BMIm OAc as an absorbent to recover SO2 in thermochemical processes to produce hydrogen. Int. J. Hydrogen Energy 2010, 35:10173–10178. 44. Lee KY, Kim CS, Kim H, Cheong M, Mukherjee DK, Jung K-D: Effects of halide anions to absorb SO2 in ionic liquids. Bull. Kor. Chem. Soc. 2010, 31:1937–1940. 45. Hou Y, Ren S, Wu W: Absorption and separation of SO2 by ionic liquids. Prog. Chem. 2011, 23:2031–2037. 46. Wang C, Cui G, Luo X, Xu Y, Li H, 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. 47. Shang Y, Li H, Zhang S, Xu H, Wang Z, Zhang L, Zhang J: Guanidinium-based ionic liquids for sulfur dioxide sorption. Chem. Eng. J. 2011, 175:324–329. 48. Yang ZZ, He LN, Song QW, Chen KH, Liu AH, Liu XM: Highly efficient SO2 absorption/activation and subsequent utilization by polyethylene glycol-functionalized Lewis basic ionic liquids. Phys. Chem. Chem. Phys. 2012, 14:15832. 49. Tailor R, Ahmadalinezhad A, Sayari A: Selective removal of SO2 over tertiary amine-containing materials. Chem. Eng. J. 2014, 240:462–468. 50. Huang J, Riisager A, Wasserscheid P, Fehrmann R: Reversible physical absorption of SO2 by ionic liquids. Chem. Commun. 2006:4027–4029. Current Opinion in Green and Sustainable Chemistry 2017, 5:74–81

80 Green Solvents 2017

51. Zeng S, Gao H, Zhang X, Dong H, Zhang X, Zhang S: Efficient and reversible capture of SO2 by pyridinium-based ionic liquids. Chem. Eng. J. 2014, 251:248–256.

and the solubility of H2S can reach 0.546 mol/mol IL1 (1 bar) and 0.225 mol/mol IL (0.1 bar), and the selectivity of H2S/CO2 can reach 37.2 at 1 bar and 15.4 at 1 bar in the hydrophobic protic ILs at 298.2 K.

52. Hong SY, Im J, Palgunadi J, Lee SD, Lee JS, Kim HS, Cheong M, Jung K-D: Ether-functionalized ionic liquids as highly efficient SO2 absorbents. Energy Environ. Sci. 2011, 4:1802–1806.

68. Huang K, Feng X, Zhang XM, Wu YT, Hu XB: The ionic liquid* mediated Claus reaction: a highly efficient capture and conversion of hydrogen sulfide. Green Chem. 2016, 18:1859–1863. Ionic liquids worked as efficient media for the liquid-phase Claus reaction of H2S with SO2 to result in solid sulfur (S8) under mild conditions without the addition of any catalysts and [Hmim][Cl] was found to be the most effective one and the transformation of H2S to S8 with a conversion ratio as high as > 96% within 3 min.

53. Zeng S, He H, Gao H, Zhang X, Wang J, Huang Y, Zhang S: * Improving SO2 capture by tuning functional groups on the cation of pyridinium-based ionic liquids. RSC Adv. 2015, 5: 2470–2478. Three kinds of novel functionalized ionic liquids were developed by introducing a tertiary amino group, ether group and nitrile group on the pyridinium cation to improve SO2 absorption performances and [NEt2C2Py][SCN] showed the highest absorption capacity of 1.06 gSO2$gIL−1 under ambient conditions. 54. Wu WZ, Han BX, Gao HX, Liu ZM, Jiang T, Huang J: Desulfurization of flue gas: SO2 absorption by an ionic liquid. Angew. Chem. Int. Ed. 2004, 43:2415–2417.

69. Yokozeki A, Shiflett MB: Ammonia solubilities in roomtemperature ionic liquids. Ind. Eng. Chem. Res. 2007, 46: 1605–1610. 70. Yokozeki A, Shiflett MB: Vapor–liquid equilibria of ammonia+ionic liquid mixtures. Appl. Energy 2007, 84:1258–1273.

55. Yu G, Chen X: SO2 capture by guanidinium-based ionic liquids: a theoretical study. J. Phys. Chem. B 2011, 115:3466–3477.

71. Shi W, Maginn EJ: Molecular simulation of ammonia absorption in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]). AIChE J. 2009, 55: 2414–2421.

56. Ren S, Hou Y, Tian S, Chen X, Wu W: What are functional ionic liquids for the absorption of acidic gases? J. Phys. Chem. B 2013, 117:2482–2486.

72. Li G, Zhou Q, Zhang X, LeiWang, Zhang S, Li J: Solubilities of ammonia in basic imidazolium ionic liquids. Fluid Phase Equilib. 2010, 297:34–39.

57. Cui G, Wang C, Zheng J, Guo Y, Luo X, Li H: Highly efficient SO2 capture by dual functionalized ionic liquids through a combination of chemical and physical absorption. Chem. Commun. 2012, 48:2633–2635.

73. Palomar J, Gonzalez-Miquel M, Bedia J, Rodriguez F, Rodriguez JJ: Task-specific ionic liquids for efficient ammonia absorption. Sep. Purif. Technol. 2011, 82:43–52.

58. 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. 59. Zeng S, Zhang X, Gao H, He H, Zhang X, Zhang S: SO2-Induced * variations in the viscosity of ionic liquids investigated by in situ fourier transform infrared spectroscopy and simulation calculations. Industrial Eng. Chem. Res. 2015, 54: 10854–10862. The effect of SO2 on the densities and viscosities during absorption processes of pyridinium-based ionic liquids (ILs) was investigated and the viscosity changes of the functionalized IL [NEt2C2Py][SCN] during SO2 absorption experienced two stages, implying the chemical and physical absorption process. 60. Chen J-J, Li W-W, Yu H-Q, Li X-L: Capture of H2S from binary gas mixture by imidazolium-based ionic liquids with nonfluorous anions: a theoretical study. AIChE J. 2013, 59:3824–3833. 61. Pomelli CS, Chiappe C, Vidis A, Laurenczy G, Dyson PJ: Influence of the interaction between hydrogen sulfide and ionic liquids on solubility: experimental and theoretical investigation. J. Phys. Chem. B 2007, 111:13014–13019. 62. Aparicio S, Atilhan M: Computational study of hexamethylguanidinium lactate ionic liquid: a candidate for natural gas sweetening. Energy Fuels 2010, 24:4989–5001. 63. Sakhaeinia H, Taghikhani V, Jalili AH, Mehdizadeh A, Safekordi AA: Solubility of H2S in 1-(2-hydroxyethyl)-3methylimidazolium ionic liquids with different anions. Fluid Phase Equilib. 2010, 298:303–309. 64. Huang K, Cai D-N, Chen Y-L, Wu Y-T, Hu X-B, Zhang Z-B: Dual Lewis base functionalization of ionic liquids for highly efficient and selective capture of H2S. Chempluschem 2014, 79: 241–249. 65. Ma YQ, Wang R: H2S absorption capacity and regeneration performance of amine Fe-based ionic liquid. Chem. J. Chin. Univ. Chin. 2014, 35:760–765. 66. Huang K, Wu YT, Hu XB: Effect of alkalinity on absorption capacity and selectivity of SO2 and H2S over CO2: substituted benzoate-based ionic liquids as the study platform. Chem. Eng. J. 2016, 297:265–276.

74. Bedia J, Palomar J, Gonzalez-Miquel M, Rodriguez F, Rodriguez JJ: Screening ionic liquids as suitable ammonia absorbents on the basis of thermodynamic and kinetic analysis. Sep. Purif. Technol. 2012, 95:188–195. 75. Li Z, Zhang X, Dong H, Zhang X, Gao H, Zhang S, Li J, Wang C: Efficient absorption of ammonia with hydroxyl-functionalized ionic liquids. RSC Adv. 2015, 5:81362–81370. 76. Shang D, Zhang X, Zeng S, Jiang K, Gao H, Dong H, Yang Q, * Zhang S: Protic ionic liquid [Bim][NTf2] with strong hydrogen bond donating ability for highly efficient ammonia absorption. Green Chem. 2017, 19:937–945. Three kinds of typical ILs were designed and applied to absorb NH3 and the protic ionic liquid [Bim][NTf2] with moderate pKa value exhibited the highest NH3 absorption capacity, up to 2.69 mol NH3/mol IL, 313 K, 100 kPa. 77. Gmehling J: Present status of group-contribution methods for the synthesis and design of chemical processes. Fluid Phase Equilib. 1998, 144:37–47. 78. Gmehling J: Present status and potential of group contribution methods for process development. J. Chem. Thermodyn. 2009, 41:731–747. 79. Klamt A, Schuurmann G: COSMO a new approach to dielectric screening in solvents with explicit expressions for the screening energy and its gradient. J. Chem. Soc. Perkin. Trans. 1993, 2 2:799. 80. Eckert F, Klamt A: Fast solvent screening via quantum chemistry COSMO-RS approach. AIChE J. 2002, 48:369–385. 81. Zhang X, Liu Z, Wang W: Screening of ionic liquids to capture CO2 by COSMO-RS and experiments. AIChE J. 2008, 54: 2717–2728. 82. Maiti A: Theoretical screening of ionic liquid solvents for carbon capture CHEMSUSCHEM 2. 2009:628–631. http://onlinelibrary. wiley.com/wol1/doi/10.1002/cssc.200900086/abstract. 83. Mortazavi-Manesh S, Satyro M, Marriott RA: A semiempirical Henry’s Law expression for carbon dioxide dissolution in ionic liquids. Fluid Phase Equilib. 2011, 307:208–215.

67. Huang K, Zhang XM, Hu XB, Wu YT: Hydrophobic protic ionic * liquids tethered with tertiary amine group for highly efficient and selective absorption of H2S from CO2. AIChE J. 2016, 62: 4480–4490. A class of novel hydrophobic protic ionic liquids containing free tertiary amine group as functional site for the absorption of H2S were designed

84. Liu X, Huang Y, Zhao Y, Gani R, Zhang X, Zhang S: Ionic liquid * design and process simulation for decarbonization of shale gas. Ind. Eng. Chem. Res. 2016, 55:5931–5944. Considering the CO2 solubility, CO2/CH4 selectivity, viscosity and toxicity of ILs, a more comprehensive COSMO-RS screening method is proposed and process design with the screened IL was developed and the result shows that the IL-based process can realize energy-saving and environmentally friendly.

Current Opinion in Green and Sustainable Chemistry 2017, 5:74–81

www.sciencedirect.com

Ionic liquids in gas separation processing Shang et al.

81

85. Fallanza M, González-Miquel M, Ruiz E, Ortiz A, Gorri D, Palomar J, Ortiz I: Screening of RTILs for propane/propylene separation using COSMO-RS methodology. Chem. Eng. J. 2013, 220:284–293.

93. Ruiz E, Ferro VR, de Riva J, Moreno D, Palomar J: Evaluation of ionic liquids as absorbents for ammonia absorption refrigeration cycles using COSMO-based process simulations. Appl. Energy 2014, 123:281–291.

86. Zhao X, Yang Q, Xu D, Bao Z, Zhang Y, Su B, Ren Q, Xing H: Design and screening of ionic liquids for C2H2/C2H4 separation by COSMO-RS and experiments. AIChE J. 2015, 61:2016–2027.

94. Deng J, Bai L, Zeng S, Zhang X, Nie Y, Deng L, Zhang S: Ether* functionalized ionic liquid based composite membranes for carbon dioxide separation. RSC Adv. 2016, 6:45184–45192. A series of composite membranes composed of ether-functionalized pyridinium-based ionic liquids were developed to conduct the CO2 separation experiment and the results showed that the CA+40 wt% [E1Py][NTf2] composite membrane exhibited a seven-fold increase in CO2 permeability with CO2/N2 and CO2/CH4 permselectivities of 32 and 24.

87. Huang Y, Dong H, Zhang X, Li C, Zhang S: A new fragment contribution-corresponding states method for physicochemical properties prediction of ionic liquids. AIChE J. 2013, 59:1348–1359. 88. Huang Y, Zhang X, Zhang X, Dong H, Zhang S: Thermodynamic modeling and assessment of ionic liquid-based CO2 capture processes. Ind. Eng. Chem. Res. 2014, 53:11805–11817.

95. Gin DL, Noble RD: Designing the next generation of chemical separation membranes. Science 2011, 332:674.

89. Shiflett MB, Drew DW, Cantini RA, Yokozeki A: Carbon dioxide capture using ionic liquid 1-butyl-3-methylimidazolium acetate. Energy Fuel 2010, 24:5781–5789.

96. Sezginel KB, Keskin S, Uzun A: Tuning the gas separation performance of CuBTC by ionic liquid incorporation. Langmuir 2016, 32:1139–1147.

90. Shifletta MB, Shiflett AD, Yokozeki A: Separation of tetrafluoroethylene and carbon dioxide using ionic liquids. Sep. Purif. Technol. 2011, 79:357–364.

97. Ban Y, Li Z, Li Y, Peng Y, Jin H, Jiao W, Guo A, Wang P, Yang Q, * Zhong C, Yang W: Confinement of ionic liquids in nanocages: tailoring the molecular sieving properties of ZIF-8 for membrane-based CO2 capture. Angew. Chem. Int. Ed. 2015, 54:15483–15487. Confining room temperature ionic liquid [Bmim][NTf2] into the nanocages of ZIF-8 through an in-situ ionothermal synthesis method, achieving an effective alteration of the molecular sieving properties of ZIF-8. Mixed matrix membranes containing IL-modified ZIF-8 showed great potential to separate CO2 from CO2/N2.

91. Basha OM, Keller MJ, Luebke DR, Resnik KP, Morsi BI: Development of a conceptual process for selective CO2 capture from fuel gas streams using [hmim][Tf2N] ionic liquid as a physical solvent. Energy Fuels 2013, 27:3905–3917. 92. Xu Y, Huang Y, Wu B, Zhang X, Zhang S: Biogas upgrading technologies: energetic analysis and environmental impact assessment. Chin. J. Chem. Eng. 2015, 23:247–254.

www.sciencedirect.com

Current Opinion in Green and Sustainable Chemistry 2017, 5:74–81