Efficient Ag2O–Ag2CO3 Catalytic Cycle and Its Role in Minimizing the

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Cite This: ACS Sustainable Chem. Eng. 2019, 7, 10234−10240

Efficient Ag2O−Ag2CO3 Catalytic Cycle and Its Role in Minimizing the Energy Requirement of Amine Solvent Regeneration for CO2 Capture Umair H. Bhatti,†,‡ Dharmalingam Sivanesan,† Sungchan Nam,† Sung Youl Park,† and Il Hyun Baek*,† †

Korea Institute of Energy Research, 217 Gajeong-ro Yuseong-gu, Daejeon 34129, South Korea University of Science and Technology, 217 Gajeong-ro Yuseong-gu, Daejeon 34113, South Korea

‡

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S Supporting Information *

ABSTRACT: The worldwide large-scale deployment of the state-of-the-art CO2 capture technique is being delayed due to the overwhelmingly high energy consumption in the stripper. Here, we reveal an efficient Ag2O−Ag2CO3 catalytic cycle and analyze its activity in the amine solvent regeneration step which is capable of greatly minimizing the energy requirement by desorbing greater amounts of CO2 at up to 1000% higher desorption rate, at low temperature, e.g. 80 °C. After substantially improving the CO2 desorption, the Ag2O converts into Ag2CO3 which is even more efficient. The Ag2CO3 ultimately decomposes into Ag2O in the amine regeneration step, and this cycle continues. The validity of the cyclic catalytic behavior was tested for ten cycles. Furthermore, the mechanism of Ag2O/Ag2CO3 facilitated CO2 desorption was elucidated using 1H and 13C nuclear magnetic resonance spectroscopy. KEYWORDS: CO2 capture, Amine, Ag2O−Ag2CO3, Catalytic cycle, Nuclear magnetic resonance

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INTRODUCTION Thermal amine scrubbing is the most mature and commercially available climate change mitigation technique, projected to play a vital role in controlling the CO2 emissions.1−4 However, high capital cost and the huge amount of energy required for amine solvent regeneration remain major deficiencies of this technique, and are considered the main reasons delaying the construction of hundreds and thousands of largescale CO2 capture plants, which are essential to achieving the “well below 2 °C” warming goal set by the Paris climate accord (COP21).5,6 Despite significant attention from industrial and academic groups for many decades, the commercialization of the amine-based postcombustion CO2 capture technology remains limited to a couple of operating facilities.7,8 Obviously, this method has yet to fulfill its potential role in controlling CO2 concentrations in the atmosphere.9 The primary shortfalls of this technique are highly energy intensive solvent regeneration, solvent degradation, and facility corrosion.3,10 In particular, the energy requirement for solvent regeneration accounts for around 70% of the total process cost, and is the most significant economic penalty.11−13 In the past two decades, many researchers have attempted to overcome the large heat duty drawback by screening/ synthesizing energy-efficient amine solvents. Chawdhury et al. studied many amine solvents and found several potential solvents which have lower heat of reaction, higher absorption capacity, and can be regenerated efficiently.14−16 Diethylenetriamine (DETA) and triethylenetetramine (TETA) and have © 2019 American Chemical Society

also been studied and found to have a lower regeneration heat duty than the benchmark monoethanolamine (MEA) solvent.17,18 Guo et al. studied nonaqueous MEA and DEA amine solvents and concluded that the solvent regeneration energy can be reduced up to 50%.19 Recently, catalyst-aided regeneration has emerged as an energy-efficient and environmentally promising technique enabling the CO2-rich amine solvent to be regenerated at low temperature.20 The catalyst weakens the N−C bond of the carbamate, which is the main form of CO2 absorbed species in the primary and secondary amines, and subsequently releases the CO2 at lower temperatures.21 Liang et al. reported that HZSM5 and γ-Al2O3 catalysts can facilitate the MEA solvent regeneration and considerably minimize the heat requirement.21 Zhang et al. analyzed the catalytic performances of SAPO-34, SO42−/TiO2, and Al2O3/HZSM-5 catalysts and demonstrated that substantial reduction in the solvent regeneration heat duty is possible.22,23 Various solid metal oxides, TiO(OH)2, and metal ions have also been reported to facilitate the CO2 desorption at lower temperature and thus minimizing the overall heat requirement for solvent regeneration.24−28 The current work reveals a novel catalytic cycle and illustrates its potential in minimizing the energy heat requirement of amine solvent regeneration step. This catalytic Received: March 27, 2019 Revised: May 23, 2019 Published: May 30, 2019 10234

DOI: 10.1021/acssuschemeng.9b01709 ACS Sustainable Chem. Eng. 2019, 7, 10234−10240

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ACS Sustainable Chemistry & Engineering

Figure 1. CO2 desorption rate curves and total amounts of desorbed CO2 from amine solution without and with catalysts (a) CO2 desorption curves for MEA without and with Ag2O and Ag2CO3 catalysts, as a function of time and temperature. (b) Improvements in CO2 desorption rate from Ag2O and Ag2CO3 solutions in comparison with noncatalytic MEA solvent. (c) CO2 desorption curves for MEA without and with Ag2O and Ag2CO3 catalysts, during temperature ramp-up stage. (d) Total amounts of CO2 desorbed throughout the experiments form MEA solution without and with Ag2O and Ag2CO3 catalysts. (e) Amount of CO2 desorbed from MEA solution without and with Ag2O and Ag2CO3 catalyst, during temperature ramp-up stage.

MEA solution was loaded with CO2 at typical absorber conditions (40 °C, 15% CO2), and the CO2 loading values were determined using a total organic carbon analyzer (Analytik Jena multi N/C 3100). 100 g of CO2-rich MEA solution was used in each experiment. The catalyst was added to the CO2-rich amine solvent and the temperature of the solvent was gradually increased until it reached the desired temperature point, i.e. 82 °C (see Note 1), and was maintained there. Upon heating the amine solvent, a pure stream of CO2 started to desorb, which was mixed with an N2 flow rate of 100 mL/min prior to analysis in the gas chromatograph. All experiments were repeated thrice, and the error was found to be ∼2%, 3.9%, and 3.1% for the blank (without catalyst), Ag2O, and Ag2CO3 catalytic experiments. The regeneration performance of MEA with 5 wt % inert microporous boiling chips was also studied to examine whether the addition of solid particles would facilitate the CO2 desorption by enhancing bubble formation in the gas−liquid mixture and thereby increase the mass transfer rate. It was found that adding the inert boiling chips slightly increased the desorbed CO2 amount (∼3%); however, it did not lower the regeneration temperature (Figure S2). As a result, this effect was deemed insignificant and was not taken into account. The CO2 desorption profiles for MEA without and with Ag2O and Ag2CO3 catalysts, as a function of temperature, are presented in Figure 1a. It can be seen that, without the catalyst, the CO2 desorption rate from MEA is limited within the studied temperatures. However, at the same temperature, the Ag2O significantly increased the CO2 desorption rate and improved the solvent regeneration

cycle, apart from its high efficiency in optimizing the CO2 desorption, itself is novel, and different from the behavior of many other metal oxides for which such cyclic catalytic behavior is not available in the amine regeneration process.24 However, this article describes the activity of this cycle in the amine regeneration step only. Herein, we report an Ag2O−Ag2CO3 catalytic cycle for amine solvent regeneration that improves the CO2 desorption rate and solvent cyclic capacity at temperatures around 80 °C, which means that a substantial reduction in the regeneration heat duty is possible. As an example, the regeneration performance of the benchmark solvent, 30 wt % monoethanolamine (MEA), without and with Ag2O and Ag2CO3 was examined. The addition of the Ag2O catalyst to the MEA regeneration step was found to be effective, and the Ag2O was subsequently converted into Ag2CO3. The formation and decomposition of Ag2CO3 was confirmed using X-ray powder diffraction (XRD). More interestingly, the Ag2CO3 was even more efficient in the CO2 desorption step and ultimately converted back into Ag2O and this cycle continued. The catalytic effects of Ag 2 O and Ag 2 CO 3 in the amine regeneration are discussed using nuclear magnetic resonance (NMR) spectroscopy.

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RESULTS AND DISCUSSION The regeneration performance of CO2-rich 30 wt % MEA solvent without and with 5 wt % Ag2O and Ag2CO3 catalysts was evaluated in a semibatch reactor (shown in Figure S1) under mild temperature conditions (40−82 ± 1 °C). The 10235

DOI: 10.1021/acssuschemeng.9b01709 ACS Sustainable Chem. Eng. 2019, 7, 10234−10240

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ACS Sustainable Chemistry & Engineering

Figure 2. XRD patterns for Ag2O and Ag2CO3 (a) XRD patterns for pure Ag2O and Ag2CO3 recorded before using (b) XRD patterns for the precipitates collected at the end regeneration experiments from Ag2O and Ag2CO3 catalytic solutions.

continues. Overall, the Ag2O and Ag2CO3 catalytic solutions were responsible for improvements of around 52 and 74% in the total amount of desorbed CO2 during the experiments, respectively, in comparison with the noncatalytic MEA solution (Figure 1d). However, it is important to note that, the catalytic solutions tended to shift the CO2 desorption extensively toward the low temperature zone, and thus the improvements in desorbed CO2 for the Ag2O and Ag2CO3 catalytic solutions during the temperature ramp-up stage were around 334% and 620% of the amount of CO2 desorbed by the noncatalytic MEA solution (Figure 1e). It is to be noted that these catalysts differ from the typical behavior of a solid acid catalyst in which the catalyst accelerates the reaction rate but remains in the system unchanged until the end of the reaction. Rather, in this work, the Ag2O and Ag2CO3 catalyst act as pseudocatalysts, which accelerate the reaction rate and convert to other species. However, this conversion follows a strict pattern (formation of Ag2CO3 from Ag2O and decomposition of Ag2CO3 into Ag2O) and the same species can be obtained after every two cycles. Therefore, these catalysts do not consume irreversibly and thus cannot be regarded as sacrificial catalysts. To investigate the catalytic activity, 1H and 13C NMR spectra for MEA before and after CO2 purging, and with Ag2O and Ag2CO3 catalysts were recorded in D2O (Figure 3). For the 1H NMR spectra for the MEA−H2O and MEA−H2O− CO2 systems, the free MEA protons appeared as two triplet peaks at 3.60 and 2.72 ppm respectively for −CH2OH and −CH2NH2, while after CO2 loading the generated species were carbamate and protonated MEA (MEAH+). The respective peaks for carbamate appeared at 2.99(t) ppm and 2.55(t) ppm, and the corresponding MEAH+ peaks were at 3.19(t) ppm and 2.53(t) ppm (Figure 3a). The change in the chemical shift of the MEA protons after CO2 loading was compared with previously reported literature values.29 From the 1H NMR spectra for the MEA−H2O−CO2−Ag2O system, it can be seen that adding Ag2O into the CO2-loaded MEA solution leads to a change in the chemical shift of MEAH+ and the carbamate species (Figure 3a, Table S1). The possible interaction between the Ag2O and carbamate is shown in Figure 3a. Under basic conditions, MEAH+ interacts with Ag2O which leads to a change in the chemical shift of the protons in the NMR spectra. More importantly, the carbamate amine group is

performance accordingly. The highest CO2 desorption rate for Ag2O solution was recorded at 81 °C, which was ∼386% higher than the noncatalytic MEA solution at the same point (Figure 1b). Figure 1b shows the improvement in the CO2 desorption rate for the catalytic solutions in comparison with the noncatalytic MEA solution. Notably, the CO2 desorption rate for the Ag2O solution is quite high at the start of the experiment, at low temperatures: at those temperatures the noncatalytic MEA solution is barely desorbing any CO2 while the Ag2O substantially accelerated the CO2 desorption rate (see Figure 1c also). A higher CO2 desorption rate, especially at lower temperatures, is crucial to minimizing the amine solvent heat duty, because the heat required to vaporize the water and raise the temperature of the amine solvent and water can be extensively reduced. Further advantages of elevated desorption rates include, but are not limited to, reduced stripper column and reboiler dimensions. The catalyst collected at the end of the Ag2O catalytic regeneration experiment was examined using XRD and Fourier-transform infrared (FTIR), which confirmed the formation of Ag2CO3 via a combination of Ag2O and CO2 (Figure 2, Figure S3). With the Ag2CO3, obtained from the Ag2O regeneration experiment, the catalyst-aided regeneration experiment was conducted again under the same conditions, and the CO2 desorption rate was recorded to be even greater than that of the Ag2O catalyst. The peak value of the CO2 desorption rate for the Ag2CO3 catalytic solution was recorded at 79 °C, which was around 550% greater than the CO2 desorption rate of the noncatalytic MEA solution at the same point (Figure 1a,b). Notably, the improvement in CO2 desorption rate went as high as around 1010% (Figure 1b). This is because MEA without a catalyst is unable to desorb reasonable amounts of CO2 at lower temperature due to stable carbamate. In contrast, the Ag2O and Ag2CO3 catalysts offer a new catalytic path with lower activation energy for CO2 desorption, which results in significant CO2 desorption at lower temperatures. Another reason for the extraordinary CO2 desorption rate with the Ag2CO3 catalytic solution is that while Ag2CO3 is catalyzing the CO2 desorption reactions it is simultaneously decomposing into Ag2O and CO2 (Figure 2b). As a result, the CO2 generated by the decomposition reaction is added to the total CO2 being released from the solution. In this way, the Ag2CO3 converts back into Ag2O, and this cycle 10236

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Figure 3. NMR spectra for MEA solutions (a) 1H NMR spectra of (1) MEA+H2O, (2) MEA+H2O+CO2, (3) MEA+H2O+CO2+Ag2O, and (4) MEA+H2O+CO2+Ag2CO3. (b) 13C NMR spectra of (1) MEA+H2O, (2) MEA+H2O+CO2, (3) MEA+H2O+CO2+Ag2O, and (4) MEA+H2O +CO2+Ag2CO3.

solution led to a change in the chemical shift of the carbamate and MEAH+ (Figure 3) due to the interactions of both catalysts with carbamate and MEAH+. The widely accepted mechanism for CO2 absorption in MEA is via two step zwitterion. At high CO2 loadings, HCO3− and CO32− are present in the system, as confirmed by the NMR spectrum. The main reactions for CO2 absorption in MEA are given in eqs 1−5, and desorption is carried out by reversing these reaction.30

bound with Ag2O, which results in the change in the carbamate protons’ chemical shift. The addition of Ag2CO3 to MEA− H2O−CO2 resulted in a 1H NMR spectrum similar to that of MEA−H2O−CO2−Ag2O, which reveals that, in the solvent regeneration step, both of the catalysts are interacting with CO2-loaded MEA in a similar fashion. In the 13C NMR spectra, the free MEA shows two peaks at 63.98(C1) and 42.62 (C2), while after CO2 purging, the MEA generated six peaks in the 13C NMR spectrum (Figure 3b). The peaks at 164, 61.31, and 57.70 ppm correspond to the carbamate, while the peaks at 63.16 and 41.24 are attributed to MEAH+. The peak appearing at 160.9 ppm confirmed the presence of bicarbonate (HCO3−). The obtained peak values were compared with previously reported literature values.29 The addition of Ag2O and Ag2CO3 into the CO2-loaded MEA 10237

MEA + CO2 ↔ zwitterion ↔ MEA−COO− + H+

(1)

CO2 + H 2O ↔ CO32 − + 2H+

(2)

CO2 + H 2O ↔ HCO3− + H+

(3)

DOI: 10.1021/acssuschemeng.9b01709 ACS Sustainable Chem. Eng. 2019, 7, 10234−10240

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ACS Sustainable Chemistry & Engineering

Figure 4. Plausible reaction scheme indicating the Ag2O facilitated breakage of N−C bond in the carbamate and formation of Ag2CO3.

Figure 5. Validity and activity of the catalytic cycle. (a) XRD patterns for pure Ag and the precipitates collected at the end ninth and tenth cycles from Ag2O and Ag2CO3 catalytic solutions. (b) Amounts of CO2 desorbed from ten cyclic regeneration tests for both catalysts.

MEAH+ + HCO3− ↔ MEA + H 2O + CO2

(4)

MEAH+ + H 2O ↔ MEA + H3O+

(5)

Figure 2b) and used in the next experiments with fresh CO2rich solution. The recovered catalysts were dried under vacuum and then pretreated at 100 °C for 1 h to remove any attached amine vapors. It should be noted that the Ag2O was slightly soluble in the solution, and thus the recovered catalysts were supplemented by fresh catalyst to maintain the catalyst to amine solution ratio. Employed this way, the catalyst was tested for ten cycles (five times for each of the Ag2O and Ag2CO3 catalyst) and at the end of the ninth and tenth cycles, XRD patterns of the recovered catalysts were recorded and compared with the XRD patterns for the pure Ag2O and Ag2CO3 catalysts (Figure 5a,b). From the XRD patterns, it was confirmed that the catalytic cycle (conversion of Ag2O to Ag2CO3 and vice versa) is valid. For the XRD pattern of the catalyst recovered from the Ag2CO3 solution, a couple of minute peaks for free Ag metal were recorded. The activity of the catalysts was evaluated in terms of total amount of desorbed CO2 during regeneration experiments. The gathered data revealed that the activity of the catalysts is almost stable with just a marginal decrease over the course of ten cycles (Figure 5c). The slight decrease in the efficiency can be attributed to the mechanical regression and particle agglomerations induced by the stirring bar. Overall, the XRD

Without a catalyst, the CO2 is released by the provided thermal energy. However, based on the results obtained from NMR spectroscopy, the catalysts are evidently attaching to carbamate, and thus provide a new route with lower activation energy for CO2 release. Both catalysts can be involved in the proton donating/accepting reactions, and metal atoms can attach to the carbamate and rob its lone pair of electrons, which weakens the N−C bond and subsequently releases the CO2 at low temperatures.21 A possible reaction mechanism of Ag2O mediated CO2 desorption and subsequent formation of Ag2CO3 is shown in Figure 4. The catalytic activity of Ag2CO3 is possibly similar to that of Ag2O; the Ag2CO3 catalyst decomposes to Ag2O and CO2 and the Ag2O improves the CO2 desorption. To examine the validity and activity of the Ag2O−Ag2CO3 catalytic cycle, we tested the catalytic performance for ten cycles. The Ag2O was added to CO2-rich MEA solution and the solution was regenerated. The catalyst was recovered at the end of the experiment (which was found to be Ag2CO3, see 10238

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(8) Mumford, K. A.; Wu, Y.; Smith, K. H.; Stevens, G. W. Review of solvent based carbon-dioxide capture technologies. Front. Chem. Sci. Eng. 2015, 9, 125−141. (9) Bui, M.; Adjiman, C.; Bardow, A.; Anthony, E.; Boston, A.; Brown, S.; Fennell, P.; Fuss, S.; Galindo, A.; Hackett, L.; Hallett, J.; Herzog, H.; Jackson, G.; Kemper, J.; Krevor, S.; Maitland, G.; Matuszewski, M.; Metcalfe, I.; Petit, C.; Puxty, G.; Reimer, J.; Reiner, D.; Rubin, E.; Scott, S.; Shah, N.; Smit, B.; Trusler, J.; Webley, P.; Wilcox, J.; Mac Dowell, N. Carbon capture and storage (CCS): the way forward. Energy Environ. Sci. 2018, 11, 1062−1176. (10) Sreedhar, I.; Nahar, T.; Venugopal, A.; Srinivas, B. Carbon capture by absorption−path covered and ahead. Renewable Sustainable Energy Rev. 2017, 76, 1080−1107. (11) Markewitz, P.; Kuckshinrichs, W.; Leitner, W.; Linssen, J.; Zapp, P.; Bongartz, R.; Schreiber, A.; Müller, T. E. Worldwide innovations in the development of carbon capture technologies and the utilization of CO2. Energy Environ. Sci. 2012, 5, 7281−7305. (12) Feng, B.; Du, M.; Dennis, T. J.; Anthony, K.; Perumal, M. J. Reduction of energy requirement of CO2 desorption by adding acid into CO2-loaded solvent. Energy Fuels 2010, 24 (1), 213−219. (13) Shakerian, F.; Kim, K. H.; Szulejko, J. E.; Park, J. W. A comparative review between amines and ammonia as sorptive media for post-combustion CO2 capture. Appl. Energy 2015, 148, 10−22. (14) Chowdhury, F. A.; Yamada, H.; Higashii, T.; Goto, K.; Onoda, M. CO2 capture by tertiary amine absorbents: a performance comparison study. Ind. Eng. Chem. Res. 2013, 52, 8323−8331. (15) Chowdhury, F. A.; Yamada, H.; Higashii, T.; Matsuzaki, Y.; Kazama, S. Synthesis and characterization of new absorbents for CO2 capture. Energy Procedia 2013, 37, 265−272. (16) Goto, K.; Okabe, H.; Chowdhury, F. A.; Shimizu, S.; Fujioka, Y.; Onoda, M. Development of novel absorbents for CO2 capture from blast furnace gas. Int. J. Greenhouse Gas Control 2011, 5, 1214− 1219. (17) Zhang, X.; Fu, K.; Liang, Z.; Rongwong, W.; Yang, Z.; Idem, R.; Tontiwachwuthikul, P. Experimental studies of regeneration heat duty for CO2 desorption from diethylenetriamine (DETA) solution in a stripper column packed with Dixon ring random packing. Fuel 2014, 136, 261−267. (18) Luo, X.; Fu, K.; Yang, Z.; Gao, H.; Rongwong, W.; Liang, Z.; Tontiwachwuthikul, P. Experimental studies of reboiler heat duty for CO2 desorption from triethylenetetramine (TETA) and triethylenetetramine (TETA)+ N-methyldiethanolamine (MDEA). Ind. Eng. Chem. Res. 2015, 54, 8554−8560. (19) Guo, H.; Li, C.; Shi, X.; Li, H.; Shen, S. Nonaqueous aminebased absorbents for energy efficient CO2 capture. Appl. Energy 2019, 239, 725−734. (20) Liu, H.; Zhang, X.; Gao, H.; Liang, Z.; Idem, R.; Tontiwachwuthikul, P. Investigation of CO2 regeneration in single and blended amine solvents with and without catalyst. Ind. Eng. Chem. Res. 2017, 56, 7656−7664. (21) Liang, Z.; Idem, R. O.; Tontiwachwuthikul, P.; Yu, F.; Liu, H.; Rongwong, W. Experimental study on the solvent regeneration of a CO2-loaded MEA solution using single and hybrid solid acid catalysts. AIChE J. 2016, 62, 753−65. (22) Zhang, X.; Zhang, X.; Liu, H.; Li, W.; Xiao, M.; Gao, H.; Liang, Z. Reduction of energy requirement of CO2 desorption from a rich CO2-loaded MEA solution by using solid acid catalysts. Appl. Energy 2017, 202, 673−684. (23) Zhang, X.; Liu, H.; Liang, Z.; Idem, R.; Tontiwachwuthikul, P.; Al-Marri, M. J.; Benamor, A. Reducing energy consumption of CO2 desorption in CO2-loaded aqueous amine solution using Al2O3/ HZSM-5 bifunctional catalysts. Appl. Energy 2018, 229, 562−576. (24) Bhatti, U. H.; Shah, A. K.; Kim, J. N.; You, J. K.; Choi, S. H.; Lim, D. H.; Nam, S. C.; Park, Y. H.; Baek, I. H. Effects of Transition Metal Oxide Catalysts on MEA Solvent Regeneration for the PostCombustion Carbon Capture Process. ACS Sustainable Chem. Eng. 2017, 5, 5862−5868. (25) Bhatti, U. H.; Sivanesan, D.; Lim, D. H.; Nam, S. C.; Park, S.; Baek, I. H. Metal oxide catalyst-aided solvent regeneration: A

patterns and solvent regeneration results confirm the stability and validity of the catalytic cycle.

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CONCLUSIONS In summary, we report an efficient Ag2O−Ag2CO3 catalytic cycle and investigate its potential to regenerate CO2-rich amine solvents for the postcombustion CO2 capture process. The catalytic cycle can substantially improve the CO2 desorption rate at lower temperatures. The formation of Ag2CO3 from Ag2O and its decomposition was also revealed and the validity of the catalytic cycle was tested up to ten cycles. A technoeconomic analysis of Ag2O/Ag2CO3 facilitated amine solvent regeneration process is required to assess the impact of the catalyst cost on overall process economy.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.9b01709.

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Experimental procedure and setup, FTIR spectra of fresh and recovered catalysts, tabulation of NMR peak values, CO2-loading values (PDF)

AUTHOR INFORMATION

Corresponding Author

*I. H. Baek. E-mail: [email protected]. Phone: +82-42-8603648. Fax: +82-42-860-3134. ORCID

Il Hyun Baek: 0000-0002-6589-9737 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by “Next Generation Carbon Upcycling Project” (Project No. 2017M1A2A2043151) through the National Research Foundation (NRF) funded by the Ministry of Science and ICT, Republic of Korea.

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REFERENCES

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DOI: 10.1021/acssuschemeng.9b01709 ACS Sustainable Chem. Eng. 2019, 7, 10234−10240