Spontaneous Cooling Absorption of CO2 by a Polymeric Ionic Liquid

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Spontaneous Cooling Absorption of CO2 by a Polymeric Ionic Liquid for Direct Air Capture Tao Wang, Chenglong Hou, Kun Ge, Klaus S. Lackner, Xiaoyang Shi, Jun Liu, Mengxiang Fang, and Zhongyang Luo J. Phys. Chem. Lett., Just Accepted Manuscript • DOI: 10.1021/acs.jpclett.7b01726 • Publication Date (Web): 10 Aug 2017 Downloaded from http://pubs.acs.org on August 12, 2017

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The Journal of Physical Chemistry Letters

Spontaneous Cooling Absorption of CO2 by a Polymeric Ionic Liquid for Direct Air Capture Tao Wang,*,† Chenglong Hou,† Kun Ge,† Klaus S. Lackner,*,‡ Xiaoyang Shi,‡ Jun Liu,† Mengxiang Fang,† and Zhongyang Luo† †

State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, PR China

‡

School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona 85287-9309, United States

AUTHOR INFORMATION Corresponding Author *Tao Wang.: E-mail: [email protected] * Klaus S. Lackner.: E-mail: [email protected]

ACS Paragon Plus Environment

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ABSTRACT. A polymeric ionic liquid (PIL), with quaternary ammonium ions attached to the polymer matrix, displays CO2 affinity controlled by moisture. This finding led to the development of moisture swing absorption (MSA) for direct air capture (DAC) of CO2. This work aims to elucidate the role of water in MSA. For some humidity range, CO2 absorption is an endothermic process associated with concurrent dehydration of the sorbent. The thermodynamic behavior of water indicates a decreased hydrophilicity of the PIL as the mobile anion transforms from CO32- to HCO3- during CO2 absorption. The decrease in hydrophilicity drives water out of the PIL, carrying heat away. The mechanism is elucidated by molecular modeling based on density functional theory. The finding of spontaneous cooling during absorption and its mechanism in the PIL opens new possibilities for designing an air capture sorbent with a strong CO2

affinity

but

low

absorption

heat.

TOC GRAPHICS


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The interactions of water molecules and ions in liquids, on surfaces and in gases profoundly affect the performances of sorbents that involve ions interacting with gases, such as CO2, H2S and NH3. The behavior of water has been an important subject of investigation for gas separation, e.g., CO2 capture for environmental applications. Water is ubiquitous and can distinctly alter the physical and chemical properties of solid surfaces and solutions in solids.1 In some instances, water simply competes for binding sites. Most CO2 sorbents, such as activated carbon,2 zeolites3 and metal-organic frameworks (MOFs),4-5 can lose over half of their CO2 capacity due to competitive adsorption of water. With the extensive development of CO2 sorbents, water has been found to have the opposite effect through new mechanisms, such as creating a Brønsted acid on a zeolite,6 occupying open metal sites7 and altering pore structures in MOFs.8 Recently, polymeric ionic liquids (PILs) have emerged as a new family of solid CO2 sorbents, as they possess both the unique characteristics of ionic liquids and the stability of macromolecular frameworks.9-11 Similar to ionic liquids, water has distinct effects on CO2 absorption in PILs.12-13 By introducing carbonate ions into quaternary-ammonium-based PILs (Figure 1),14-17 such as poly[4-vinylbenzyltrimethylammonium] (P[VBTEA]]), several groups found that these materials can capture CO2 directly from ambient air, enabling direct air capture (DAC) as a climate management tool. The sorbents bind CO2 when dry and release CO2 when wet. Using water in moisture swing absorption (MSA) rather than heat, CO2 was separated from air with high energy efficiency. PILs are formed via polymerization of constituent monomers contained in ionic liquids. In this work, cations (quaternary ammonium ions) are attached to the polymer structure, which is infused by water and mobile ions, mainly carbonate, bicarbonate and hydroxide ions, that balance the positive charge of the polymer scaffold. This perspective on the


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process focuses on the ion-rich liquid held in place by a polymer, emphasizing the need for transport of water and ions through the ‘liquid’ and naturally considering the binding of CO2 as an absorption process on the outside of the PIL structural framework that involves diffusion in the ‘liquid’ to fill the interior of the PIL. The focus of this work is on energy changes in a quaternary-ammonium-based PIL during the MSA of CO2. The CO2 binding strength is believed to be modulated by water availability and the interaction of water with anions on P[VBTEA] (process (1) in Figure 1).15, 18-19 The binding of additional CO2 will alter the hydration state of P[VBTEA] as the anions are converted from CO32- to HCO3- and OH- (process (2)). Different ions bind different amounts of water and affect its interaction with the PIL, which is accompanied by strong hydration/dehydration heat (∆H).

Figure 1. Water behavior during MSA of a quaternary-ammonium-based PIL. R+ represents the quaternary ammonium cation. ∆H1, ∆H2 and ∆H3 are the hydration heat, CO2 absorption heat and dehydration heat, respectively. CO2 absorption may alter the hydration state of the sorbent as the anions are converted from CO32- to HCO3-. The interactions of water and CO2 on the PIL at different relative humidities (RHs) were quantitatively determined by gravimetric and calorimetric techniques at 30 °C. The preparation


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and physical/chemical properties of P[VBTEA]-[CO32-] are provided in the Supporting Information.14 As illustrated in Figure 2, the RH shifts the absorption isotherms of both H2O and CO2. A considerable dehydration phenomenon was observed with CO2 absorption under a constant RH. The experimental dehydration data fits well with a previously developed theoretical model based on the Langmuir isotherm.20 One can infer that, during CO2 absorption, water transportation in P[VBTEA]-[CO32-] should be driven by a chemical potential change of the sorbent, which enables the valid prediction of the CO2/H2O interaction under any RH. The water absorption isotherms of the sorbent in the CO32- form (CO2 free) and HCO3- form (CO2 saturated) demonstrate similar patterns corresponding to D’Arcy & Watt isotherms but display different hydrophilicities. The D’Arcy & Watt model assumes the strong interaction of water molecules with the surface,21 which was measured as the H2O absorption heat (Table 1).

Figure 2. H2O/CO2 absorption isotherms and H2O transportation of the PIL sorbent. The amount of mobilized water during CO2 absorption is well fitted with the thermodynamic model. H2O mobilized during CO2 absorption was measured with 100% CO2 to enable similar saturation states for the product under different RHs. (FG = functional group, i.e., ion pair of [2N(CH3)4+]·CO32-).


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Considering the large latent heat of water vaporization, a considerable release of water during CO2 absorption would carry substantial heat from the sorbent. The mass and heat transfers during CO2 absorption under different RHs were directly characterized by gravimetric, calorimetric and temperature measurements. As the CO2 absorption capacity drops quickly with increased RH, three RHs lower than 50% were selected as representative conditions. The calorimetric results for the absorption process under different conditions are listed in Table 1. The CO2 absorption heat under a dry atmosphere (water vapor free) at 30 °C was determined to be -72.7 kJ/mol CO2, which is similar as that of solid amines.22 However, with an increased humidity, CO2 absorption transits from an exothermic reaction to an endothermic reaction, presenting an interesting phenomenon of spontaneous cooling absorption.

Table 1. Absorption of CO2/H2O at different RHs. Temperature (°C) H2O absorption[a]

CO2 absorption[d]

RH (%)

Reaction heat (kJ/mol FG)

30

36.4[b]

-48.8

30

48.6[c]

-47.6

30

0.0

-72.7

30

15.9

82.6

30

36.4

139.6

30

48.6

173.9

[a]

Water absorption by the sorbent in CO32- form (CO2 free). RH of 36.4%. [d] Pure CO2 under 1 atm pressure.

[b]

Initial RH of 15.9%. [c] Initial

Figure 3 illustrates the heat flow evolutions during CO2 absorption. Although the total process of CO2 absorption is endothermic under RHs of 15.9% and 36.4%, a sharp exothermic peak was still observed due to the strong interaction between CO2 and the alkaline functional groups. The subsequent endothermic process (starting at approximately 20 minutes after CO2 injection)


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corresponds to a dehydration process, which lasts quite a long period (hours). As discussed above, CO2 absorption is accompanied by a dehydration process. The propagation delay of the endothermic heat flow indicates that a dynamic difference exists between CO2 and H2O transport in the PIL sorbent. The gravimetric curves also demonstrate sharp peaks, which may result from the considerable delay of H2O transport during CO2 absorption. This phenomenon could be ascribed to the different diffusion rates for species inside the PIL. The cross-linked macromolecular framework of PIL in this work has pore sizes of approximately 10 to 20 Å for ion transport23. CO2 may diffuse inside as a gas molecule or carbonate ion, where the diffusion kinetics of the latter form would not be greatly influenced by the micro-pore structure.19 On the other hand, as interfacial water is released from the PIL, the vapor partial pressure inside the confined space, especially the nanometer-sized space, would rapidly rise, inhibiting the dehydration kinetics.24 The properties of the polar H2O molecules and hydrophilic quaternary ammonium material25 can further slow the dehydration process. The difference in the diffusion kinetics between CO2 and H2O inside the confined space was also observed by both hightemperature Fourier transform infrared (HT-FTIR) spectroscopy and molecular level simulations.26-27


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Figure 3. Evolutions of heat flow and mass change of the sorbent during CO2 absorption at 30 °C. The heat flow curve under a humid atmosphere exhibits a sharp exothermic peak and a subsequent endothermic process. The corresponding temperature curve exhibited a sharp increase followed by a gradual decrease. The gravimetric curve exhibits a peak due to CO2 absorption and similar delay of H2O transportation. The unique spontaneous cooling absorption was directly demonstrated through temperature measurements on the sorbent (Supporting Information), as shown in the inset of Figure 3. Due to the delayed dehydration, the sorbent showed a sharp peak of temperature increase during CO2 absorption even for the endothermic process. With increased RH, the peak value of the temperature change declined from 15.8 K to 7.6 K due to stronger dehydration (Figure S8). A subsequent mild temperature decrease of the sorbent was observed upon dehydration, and the sorbent temperature was under the ambient temperature for quite a long period. The mild temperature increase would benefit the absorption kinetics during the initial stages. On the other hand, the temperature rise is much lower than that of conventional sorbents, which would alleviate overheating issues. For example, a rise in excess of 80 K in the sorbent temperature was observed for non-adiabatic adsorption of CO2 on a zeolite.28 Moreover, the spontaneous cooling effect during the middle and late period of gas absorption would benefit the absorption thermodynamics and ensure excellent absorption capacity. This spontaneous cooling absorption is rarely reported for CO2 absorption processes and opens new possibilities for designing an air capture sorbent with a strong CO2 affinity but low absorption heat. To reveal the mechanism of spontaneous cooling absorption and to relate the enthalpy change to the interfacial water transportation, a complete heat and mass transfer route is depicted, as shown in Figure 4. The downward paths from carbonate to bicarbonate represent the CO2


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absorption coupled with H2O migration at fixed RHs. According to mass conservation and Hess’s law, the absorption heat and mass change of Path A and B should be the same, as these paths possess the same initial and final states. With the known isothermal data of CO2/H2O absorption for the sorbent in the CO32- form (∆H, ∆H’, ∆n, ∆n’), thermodynamic behavior of water (∆H’’, ∆n’’) in the sorbent in the bicarbonate form can be determined. The relative lower ∆H’’ compared to ∆H’ indicates a decreased hydrophilicity of the PIL during CO2 absorption. Moreover, in a wide humidity range, the absorption heat of H2O is barely affected by the humidity, no matter if the sorbent in the carbonate form, ∆H’, or the bicarbonate form, ∆H’’. This observation indicates that, under most humidity conditions, the migrated water molecules during CO2 absorption should be primarily located at the outer layers of absorbed water clusters and thus have similar absorption heat. Therefore, by considering the constant values of ∆H’ and ∆H’’ and with the known water absorption isotherms and a known ∆H0 as the initial state, one can predict the absorption heat of CO2 (∆H) under any RH. This prediction could substitute extensive calorimetric measurements, which are time consuming. The equivalence of the thermodynamic paths also reveals that the difference of the hydrophilicity of the sorbent between the carbonate and bicarbonate forms should be the theoretical basis of spontaneous cooling absorption.


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Figure 4. Pathways of heat and mass transfer during MSA. Path A and B have the same initial and final states. ∆H, ∆H’ and ∆H” are the CO2 absorption heat and the water absorption heat of the carbonate and bicarbonate forms. In the case of CO32-, water molecules are uniformly located around the anion, while the water molecules self-associated or form clusters in the case of HCO3. Rg is the gyration radius of the water molecules around the anion. (Oxygen: red, nitrogen: blue, carbon: gray, hydrogen: white). To gain a deep understanding of the interaction between the interfacial water and sorbent with different ion pairs, the optimized molecular structures of the hydrated ion pairs were calculated by density functional theory (DFT), as shown in Figure 4. The spatial distribution of the interfacial water molecules is quite different for the sorbent with different counter anions. In the case of carbonate, the water molecules are uniformly located around the anion with a gyration radius (Rg) of 3.247 Å, while the water molecules self-associate or form a cluster with a Rg of 1.852 Å in the case of bicarbonate. These observations indicate the different hydrophilicity for the sorbent with different counter anions. The interactions between the interfacial water and ion pairs can be measured by the hydrogen bonds between them, which are shown in Table 2. The length of the hydrogen bonds in the case of bicarbonate was found to be larger than that of carbonate, indicating weaker intermolecular interactions. In general, a greater electronegativity of the hydrogen bond acceptor will create a stronger hydrogen bond. In a bicarbonate anion, part of the negative charge is neutralized by the added proton, which results in a decrease of the strength of the hydrogen bonds.29 More direct evidence for the different hydrophilicities can be presented by comparing the standard Gibbs free energy of hydration of the sorbent (∆G0, Supporting Information). On the other hand, with the decrease of hydration number, the O-H bond length in the most active water increases which indicates higher possibility of water


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dissociation. As much more OH- is produced through proton transfer of water, higher CO2 absorption capacity could be obtained with decreased RH 14.

Table 2. Properties of hydrated water in the model compounds of the sorbent with different anions. Anions

Hydration number

r1 [a](Å)

r2 [b] (Å)

∆G0 (kJ/mol)

CO32-

0

-

-

-29.48

1

1.001

1.654

-19.95

2

0.998

1.685

-4.42

3

0.985

1.720

-

0

-

-

-5.18

1

0.981

1.731

0.97

2

0.977

1.756

1.11

3

0.971

1.829

-

HCO3-

[a]

O-H bond length in the most active hydrated water. the most hydrated water.

[b]

The length of the hydrogen bond of

In conclusion, we demonstrated a spontaneous cooling absorption of CO2 by a PIL. The thermodynamic studies indicated a decreased hydrophilicity of the PIL as the anion transformed during CO2 absorption, inducing dehydration and cooling effects of the sorbent. The mechanism was elucidated by DFT-based molecular simulations, which showed weakened hydrogen bonds for the PIL with a bicarbonate anion. The findings shed light on a new design for PILs with low absorption heat, not only for direct air capture but also for CO2 capture from concentrated sources.

ASSOCIATED CONTENT


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AUTHOR INFORMATION *E-mail: [email protected] (T.W.); [email protected] (K.S.L.). Notes The authors declare no competing financial interests. ACKNOWLEDGMENT This study is supported by the National Natural Science Foundation of China (No. 51676169) and the Fundamental Research Funds for the Central Universities. Supporting Information Available. Material characterization, isothermal equilibriums of CO2 and H2O, calorimetric experiments, temperature measurement, and modeling methodology.

REFERENCES (1) Oncak, M.; Wlodarczyk, R.; Sauer, J. Water on the MgO(001) Surface: Surface Reconstruction and Ion Solvation. J. Phys. Chem. Lett. 2015, 6, 2310-2314. (2) Sevilla, M.; Fuertes, A. B. Sustainable Porous Carbons with a Superior Performance for CO2 Capture. Energy Environ. Sci. 2011, 4, 1765-1771. (3) Stuckert, N. R.; Yang, R. T. CO2 Capture from the Atmosphere and Simultaneous Concentration Using Zeolites and Amine-grafted SBA-15. Environ. Sci. Technol. 2011, 45, 10257-10264. (4) Yu, J.; Balbuena, P. B. Water Effects on Postcombustion CO2 Capture in Mg-MOF74. J. Phys. Chem. C 2013, 117, 3383-3388.


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(5) Bhatt, P. M.; Belmabkhout, Y.; Cadiau, A.; Adil, K.; Shekhah, O.; Shkurenko, A.; Barbour, L. J.; Eddaoudi, M. A Fine-Tuned Fluorinated MOF Addresses the Needs for Trace CO2 Removal and Air Capture Using Physisorption. J. Am. Chem. Soc. 2016, 138, 9301-9307. (6) Wang, Q.; Luo, J.; Zhong, Z.; Borgna, A. CO2 Capture by Solid Adsorbents and Their Applications: Current Status and New Trends. Energy Environ. Sci. 2011, 4, 42-55. (7) Yazaydin, A. O.; Benin, A. I.; Faheem, S. A.; Jakubczak, P.; Low, J. J.; Willis, R. R.; Snurr, R. Q. Enhanced CO2 Adsorption in Metal-Organic Frameworks via Occupation of Open-Metal Sites by Coordinated Water Molecules. Chem. Mater. 2009, 21, 1425-1430. (8) Llewellyn, P. L.; Bourrelly, S.; Serre, C.; Filinchuk, Y.; Ferey, G. How Hydration Drastically Improves Adsorption Selectivity for CO2 over CH4 in the Flexible Chromium Terephthalate MIL-53. Angew. Chem. Int. Edit. 2006, 45, 7751-7754. (9) Tang, J. B.; Tang, H. D.; Sun, W. L.; Radosz, M.; Shen, Y. Q. Low-pressure CO2 Sorption in Ammonium-based Poly(ionic liquid)s. Polymer 2005, 46, 12460-12467. (10) Yuan, J.; Mecerreyes, D.; Antonietti, M. Poly(ionic liquid)s: An Update. Prog. Polym. Sci. 2013, 38, 1009-1036. (11) Mecerreyes, D. Polymeric Ionic Liquids: Broadening the Properties and Applications of Polyelectrolytes. Prog. Polym. Sci. 2011, 36, 1629-1648. (12) Tang, J. B.; Tang, H. D.; Sun, W. L.; Plancher, H.; Radosz, M.; Shen, Y. Q. Poly(ionic liquid)s: A New Material with Enhanced and Fast CO2 Absorption. Chem. Commun. 2005, 3325-3327. (13) Zhao, Q.; Anderson, J. L. Selective Extraction of CO2 from Simulated Flue Gas Using Polymeric Ionic Liquid Sorbent Coatings in Solid-phase Microextraction Gas Chromatography. J. Chromatogr. A 2010, 1217, 4517-4522.


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(14) Wang, T.; Lackner, K. S.; Wright, A. Moisture Swing Sorbent for Carbon Dioxide Capture from Ambient Air. Environ. Sci. Technol. 2011, 45, 6670-6675. (15) Wang, T.; Ge, K.; Chen, K.; Hou, C.; Fang, M. Theoretical Studies on CO2 Capture Behavior of Quaternary Ammonium-based Polymeric Ionic Liquids. Phys. Chem. Chem. Phys. 2016, 18, 13084-13091. (16) He, H.; Li, W.; Zhong, M.; Konkolewicz, D.; Wu, D.; Yaccato, K.; Rappold, T.; Sugar, G.; David, N. E.; Matyjaszewski, K. Reversible CO2 Capture with Porous Polymers Using the Humidity Swing. Energy Environ. Sci. 2013, 6, 488-493. (17) Wang, T.; Liu, J.; Huang, H.; Fang, M.; Luo, Z. Preparation and Kinetics of a Heterogeneous Sorbent for CO2 Capture from the Atmosphere. Chem. Eng. J. 2016, 284, 679-686. (18) Quinn, R. Ion Exchange Resins as Reversible Acid Gas Absorbents. Sep. Sci. Technol. 2003, 38, 3385-3407. (19) Shi, X.; Xiao, H.; Lackner, K. S.; Chen, X. Capture CO2 from Ambient Air Using Nanoconfined Ion Hydration. Angew. Chem. Int. Ed. 2016, 55, 4026-4029. (20) Wang, T.; Lackner, K. S.; Wright, A. B. Moisture-swing Sorption for Carbon Dioxide Capture from Ambient Air: A Thermodynamic Analysis. Phys. Chem. Chem. Phys. 2013, 15, 504-514. (21) Terzyk, A. P.; Rychlicki, G.; Gauden, P. A. Energetics of Water Adsorption and Immersion on Carbons: Part 2. Adsorption on Non-modified, Oxidised, and Modified via Ionic Exchange Carbons from Polyfurfuryl Alcohol. Colloids Surf. A: Physicochem. Eng. Aspects 2001, 179, 39-55. (22) Alkhabbaz, M. A.; Bollini, P.; Foo, G. S.; Sievers, C.; Jones, C. W. Important Roles of Enthalpic and Entropic Contributions to CO2 Capture from Simulated Flue Gas and Ambient Air Using Mesoporous Silica Grafted Amines. J. Am. Chem. Soc. 2014, 136, 13170-13173.


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(23) Grubhofer, V. N. Zur struktur von mit divinylbenzol vernetzten polystyrollonenaustauschern. Makromol. Chem. 1959, 30, 96-108. (24) Hanot, S.; Lyonnard, S.; Mossa, S. Sub-diffusion and Population Dynamics of Water Confined in Soft Environments. Nanoscale 2016, 8, 3314-3325. (25) Shishatskiy, S.; Pauls, J. R.; Nunes, S. P.; Peinemann, K. V. Quaternary Ammonium Membrane Materials for CO2 Separation. J. Membr. Sci. 2010, 359, 44-53. (26) Svoboda, M.; Brennan, J. K.; Lísal, M. Molecular Dynamics Simulation of Carbon Dioxide in Single-walled Carbon Nanotubes in the Presence of Water: Structure and Diffusion Studies. Mol. Phys. 2015, 113, 1124-1136. (27) Radica, F.; Della Ventura, G.; Bellatreccia, F.; Cinque, G.; Marcelli, A.; Guidi, M. C. The Diffusion Kinetics of CO2 in Cordierite: An HT-FTIR Microspectroscopy Study. Contrib. Mineral. Petrol. 2016, 171, 12. (28) Mulgundmath, V. P.; Jones, R. A.; Tezel, F. H.; Thibault, J. Fixed Bed Adsorption for the Removal of Carbon Dioxide from Nitrogen: Breakthrough Behaviour and Modelling for Heat and Mass Transfer. Sep. Purif. Technol. 2012, 85, 17-27. (29) Sanderson, R. T. Electronegativity and Bond Energy. J. Am. Chem. Soc. 1983, 105, 2259-2261.


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Water behavior during MSA of a quaternary-ammonium-based PIL. R+ represents the quaternary ammonium cation. ∆H1, ∆H2 and ∆H3 are the hydration heat, CO2 absorption heat and dehydration heat, respectively. CO2 absorption may alter the hydration state of the sorbent as the anions are converted from CO32- to HCO3-. 41x21mm (600 x 600 DPI)


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H2O/CO2 absorption isotherms and H2O transportation of the PIL sorbent. The amount of mobilized water during CO2 absorption is well fitted with the thermodynamic model. H2O mobilized during CO2 absorption was measured with 100% CO2 to enable similar saturation states for the product under different RHs. (FG = functional group, i.e., ion pair of [2N(CH3)4+]·CO32-). 56x38mm (600 x 600 DPI)



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Evolutions of heat flow and mass change of the sorbent during CO2 absorption at 30 °C. The heat flow curve under a humid atmosphere exhibits a sharp exothermic peak and a subsequent endothermic process. The corresponding temperature curve exhibited a sharp increase followed by a gradual decrease. The gravimetric curve exhibits a peak due to CO2 absorption and similar delay of H2O transportation. 56x39mm (600 x 600 DPI)


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Pathways of heat and mass transfer during MSA. Path A and B have the same initial and final states. ∆H, ∆H’ and ∆H” are the CO2 absorption heat and the water absorption heat of the carbonate and bicarbonate forms. In the case of CO32-, water molecules are uniformly located around the anion, while the water molecules self-associated or form clusters in the case of HCO3-. Rg is the gyration radius of the water molecules around the anion. (Oxygen: red, nitrogen: blue, carbon: gray, hydrogen: white). 59x42mm (600 x 600 DPI)



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TOC 49x49mm (300 x 300 DPI)


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Spontaneous Cooling Absorption of CO2 by a Polymeric Ionic Liquid

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