Energyless CO2 absorption, generation, and fixation using atmospheric CO2

Article abstract of DOI:10.1248/cpb.c15-00793

From an economic and ecological perspective, the efficient utilization of atmospheric CO₂ as a carbon resource should be a much more important goal than reducing CO₂ emissions. However, no strategy to harvest CO₂ using atm

Full text of DOI:10.1248/cpb.c15-00793

8
Chem. Pharm. Bull. 64, 8–13 (2016)
Vol. 64, No. 1
Communication to the Editor
CO gas from chemical absorbent requires heating at high
Energyless CO Absorption, Generation,
and Fixation Using Atmospheric CO2
2
2
temperature, which uses high amount of electricity. This
means that introducing CCS plants spends one part of electric-
generating capacity in power station. The limited number of
sites is also problematic because CCS plants must be con-
Fuyuhiko Inagaki,* Yasuhiko Okada,
Chiaki Matsumoto, Masayuki Yamada,
Kenta Nakazawa, and Chisato Mukai
structed near areas with high CO
use solar light and a metal catalyst. In this approach, CO is
densities. In contrast, APSs
2
2
12)
13)
transformed into HCO H or CO, whereby the products can
2
Division of Pharmaceutical Sciences, Graduate School of
Medical Sciences, Kanazawa University; Kakuma-machi,
Kanazawa 920–1192, Japan.
Received October 15, 2015; accepted November 10, 2015; advance
publication released online November 20, 2015
be converted to sources of energy (such as methanol). The use
of this system is more valuable than CCS from an economic
perspective; however, APSs have been shown to work only
when high concentrations of CO (>1atm) are present. Plant-
2
ing trees and developing alternative energy resources (e.g., H2,
biofuel, and solar power) are also ongoing activities. Unfortu-
From an economic and ecological perspective, the efficient
utilization of atmospheric CO as a carbon resource should nately, planting trees does not offer an immediate economic
2
be a much more important goal than reducing CO emissions. benefit,ꢀ andꢀ fossilꢀ fuelsꢀ remainꢀ theꢀ cheapestꢀ energyꢀ source.ꢀ
2
However, no strategy to harvest CO using atmospheric CO2 Continuous efforts to establish a more promising method for
2
at room temperature currently exists, which is presumably
due to the extremely low concentration of CO2 in ambient
air (approximately 400ppmꢀ0.04vol%). We discovered that
monoethanolamine (MEA) and its derivatives efficiently ab-
CO reduction are needed. Clearly, the lack of an immediate
2
economic advantage for CO reduction prevents positive ac-
2
tion toward solving this issue. In this regard, an indirect eco-
21)
nomic approach called “carbon emission trading” has been
introduced. This concept is currently one of the most effective
tactics for reducing carbon dioxide production, although it is
sorbed atmospheric CO without requiring an energy source.
2
We also found that the absorbed CO could be easily liberated
2
with acid. Furthermore, a novel CO generator enabled us to
2
yet to limit CO production to an ideal level. To address these
synthesize a high value-added material (i.e., 2-oxazolidinone
2
derivatives based on the metal catalyzed CO -fixation at room problems, we developed an “energyless CO
ꢀfixation”ꢀmethod,ꢀ
2
2
temperature) from atmospheric CO2.
or ECO -fix.ꢀECO -fixꢀisꢀaꢀnovelꢀatmosphericꢀCO ꢀfixationꢀre-
2
2
2
action that does not require energy input, such as solar power,
Key words carbon dioxide absorption; carbon dioxide gener-
ation;ꢀcarbonꢀdioxideꢀfixation;ꢀcyclization;ꢀatmosphericꢀchemistry
heating, cooling, or stirring. Moreover, ECO -fixꢀalsoꢀhasꢀtheꢀ
2
capacity to produce high value-added materials, such as pre-
cursors of medicines, chemical products, and energy sources.
In 2014, the Intergovernmental Panel on Climate Change ECO -fixꢀ hasꢀ fourꢀ majorꢀ advantages.ꢀ First,ꢀ theꢀ reactionꢀ
2
1)
(
IPCC) reported that warming of the climate is unequivo- absorbs CO , which mimics processes that occur in plants.
2
cal and that the largest contribution is a result of increasing Second, the valuable products generated from CO possess
2
atmospheric CO since 1750. In the previous year, the National financialꢀvalue.ꢀThird,ꢀcarbonꢀcreditsꢀcanꢀstillꢀbeꢀtradedꢀbasedꢀ
2
Oceanic and Atmospheric Administration (NOAA) in Mauna on the quantity of CO ꢀthatꢀcanꢀbeꢀfixed.ꢀFinally,ꢀregardlessꢀofꢀ
2
Loa, Hawaii, observed that the concentration of atmospheric geographic location, CO is abundant in the atmosphere. Thus,
2
CO ꢀsurpassedꢀ400ꢀppmꢀforꢀtheꢀfirstꢀtimeꢀsinceꢀmeasurementsꢀ the development of ECO -fixꢀwillꢀprovideꢀbothꢀecologicalꢀandꢀ
2
2
began in 1958. This value is approximately 120ppm higher economicꢀbenefits.
than that of the pre-industrial atmosphere (approximately
Since the discovery of the famous Kolbe–Schmidt
2)
22,23)
24)
2
80 ppm). Global CO emissions from fuel combustion in reaction
and Grignard reaction with CO , several CO
2
2 2
2
5–47)
2
012 reached a record of 31.7 gigatons (GtCO ) based on fixationꢀ methodsꢀ haveꢀ beenꢀ reportedꢀ inꢀ theꢀ literature.
2
calculations performed by the International Energy Agency However, no methods for CO ꢀfixationꢀareꢀsimilarꢀtoꢀECO -fix,ꢀ
2
2
3
)
(
IEA). On the other hand, there are many reports that CO
which is presumably due to the extremely low concentrations
The experi- of CO (approximately 400ppm, or 0.04%) in the ambient air.
2
4
–10)
is not an essential source for Climate Change.
2
mental fact can only prove the answer of these discussions. Air also contains other reactive species, including O (20%)
2
Thus, techniques for reduction of CO must be globally im- and water (approximately 0.4%, depending on the environ-
2
portant.
ment), which may prevent the desired reactions. Therefore,
14–20)
Current efforts for CO reduction include CO2 capture we focused on monoethanolamine (MEA 1),
which is a
and storage (CCS) ꢀ andꢀ artificialꢀ photosyntheticꢀ systemsꢀ chemical absorbent that is capable of capturing CO ꢀfromꢀflueꢀ
2
11)
2
1
2,13)
(
APSs).
CCS involves the capture of CO using chemical gas or other gaseous streams. Normal carbamic acid rapidly
2
14–20)
absorbent (i.e., monoethanolamine, MEA 1 etc.)
in high- decarboxylates to form an amine while liberating CO . The
2
density areas, such as industrial facilities and power stations, hydroxyethyl moiety of MEA 1 is crucial for trapping CO2,
and transporting CO to deep subsurface rock formations or whichꢀ isꢀ usefulꢀ informationꢀ forꢀ developingꢀ aꢀ methodꢀ toꢀ fixꢀ
2
the bottom of the ocean via pipelines. This is a useful and CO from the atmosphere. Nevertheless, the ability of MEA
2
efficientꢀtechniqueꢀthatꢀcanꢀpreventꢀtheꢀreleaseꢀofꢀlargeꢀquanti- 1 and its derivatives to absorb atmospheric CO has been un-
2
ties of CO . However, this technology does not provide any developed.ꢀThus,ꢀweꢀfirstꢀtestedꢀCO absorption from ambient
2
2
immediateꢀ economicꢀ benefit,ꢀ andꢀ theꢀ capturedꢀ CO2 is not air. For this experiment, we prepared a battery-powered CO2
chemically altered. In the projects of CCS, the liberation of monitor and dessicator (dimensions of 465×290×265mm,
*
ꢀToꢀwhomꢀcorrespondenceꢀshouldꢀbeꢀaddressed.ꢀ e-mail:ꢀfinagaki@p.kanazawa-u.ac.jp
©
2016 The Pharmaceutical Society of Japan

Vol. 64, No. 1 (2016)
Chem. Pharm. Bull.
9
Fig. 1. MEA and Its Derivatives Absorb Atmospheric CO without Consuming Energy
2
The individual panels show the ability of monoethanolamine derivatives (5mmol) to absorb CO2 (1: monoethanolamine (MEA), 2: diethanolamine (DEA), 3: triethanol-
amine (TEA), 4: 2-(methylamino)ethanol (MAE), 5: 2-amino-2-methylpropan-1-ol (AMP), 6: phenylglycinol (PG)). CO2 concentrations were measured using a CO2 moni-
tor in the sealed box. a) The desiccator used in these experiments had dimensions of 465×290×265mm (with a volume of 35.7L). After setting the absorbent on a Petri
dish and sealing the system, the CO2 concentration was measured using a CO2 monitor. b) The initial CO2 concentrations in our experiments ranged from 437 to 573ppm
(
0.70–0.91mmol CO ). The concentrations were monitored every 30min.
2
with a total volume of 35.7L) to monitor CO absorption in functionalities were also tested and were found to be less ef-
2
an enclosed space. The results are shown in Figs. 1a and b. fective than MEA 1.ꢀSpecifically,ꢀtheꢀCO absorption ability of
2
The initial CO concentration (437–573ppm, 0.70–0.91mmol diethanolamine (DEA 2) was lower than that of MEA 1, and
2
CO ) was highly dependent on uncontrollable variables in the absorption of CO by triethanolamine (TEA 3) was unde-
2
2
the experimental room, including the time, season, number tected. Thus, we concluded that MEA and certain derivatives
of people present, and air from ventilation. When 0.33mL with suitable functional groups are “active CO2 absorption
(5.0mmol) of MEA 1 was incubated in the sealed box, the species,” even under ambient pressures.
CO2 concentration immediately decreased from 551ppm to Next, we investigated the ratio of CO absorption in air
2
less than 10ppm within 17h. When 10mL of MEA 1 was using MEA 1. As shown in Fig. 2a, MEA 1 was placed on
incubated in the chamber, the concentration of CO reached a scale exposed to air and its weight was measured over
2
0
ppm after 6.5h. These results suggest that a large excess time. The average masses of MEA 1 over time from three
of MEA 1 in the atmosphere could reduce the global CO2 replicates are shown in Fig. 2b. While MEA 1 is a volatile
concentration (400ppm) to its pre-industrial level (280ppm) species, our results clearly indicate that the rate of CO ab-
2
within several hours. Next, we tested several MEA derivatives sorption is faster than that of evaporation. In our study, CO2
for their ability to absorb CO in the sealed box. The absorp- absorption reached equilibrium after approximately 1.5d. To
2
tion ability of N-methylated 2-(methylamino)ethanol (MAE 4) determine the composition of the mixture, elemental analy-
was similar to that of MEA 1. Next, we tested α-substituted ses were conducted (Fig. 2a). Samples collected after 1 and
derivatives of MEA 1. However, 2-amino-2-methylpropan-1-ol 7d were compared and analysed, revealing that the former
(
AMP 5) absorbed less CO than that of MEA 1, and phenylg- had not yet reached equilibrium. In addition, the elemental
2
lycinol (PG 6) did not reduce the concentration of CO in the analysis of the sample collected after 7d suggested that the
2
studied air. Derivatives of MEA having multiple hydroxyethyl mixture x(CO )·y(MEA)·z(H O) 7, which was at equilibrium,
2
2

1
0
Chem. Pharm. Bull.
Vol. 64, No. 1 (2016)
Fig. 2. MEA 1 Absorbs Atmospheric CO without Consuming Energy
2
a) Twenty milliliters of MEA 1 (20g, 0.33mol) was added to a Petri dish; its mass was measured over time using a balance. The ratio of structural components in the
resulting mixture was calculated from values determined by elemental analysis with ± 0.4% error. b) The CO2 absorption of MEA 1 based on measurements collected
from a balance. The masses were monitored approximately three times every 6h. c) Based on the NMR, IR, and elemental analysis, plausible structure of 7 was shown.
Fig. 3. Energyless CO Fixation under Atmospheric Conditions Occurs Only with Substrates Containing a N-Hydroxyethyl Functionality
2
Equation 1 shows Au or Ag catalysed reactions of propargylamine derivatives that do not possess a N-hydroxyethyl functionality. The reactions did not proceed. Equa-
tion 2 shows Au-catalysed CO ꢀfixationꢀofꢀHEPAꢀ10. Equation 3 shows metal-catalysed CO ꢀfixationꢀofꢀsubstitutedꢀHEPAꢀderivativesꢀ12. All reactions were performed and
2
2
analysed at least twice.
contained CO , MEA 1, and H O at a ratio of approximately sorption of CO ꢀtoꢀtheꢀfixationꢀofꢀCO without consuming ex-
2
2
2
2
1
:3:3. Water would be derived from moisture in atmosphere. ternal energy. For this purpose, a reaction in which urethana-
−1
13
Judging from the values of IR (1480cm ) and C-NMR (δ tion of propargylamines forms oxazolidinone derivatives using
39,41,47)
164.8), absorbed CO would be transformed into carbonate. a metal catalyst
was selected. Many types of pharmaco-
2
The plausible structure of 7 was shown in Fig. 2c. The chemi- logically active compounds containing oxazolidinone frame-
4
8,49)
cal yields of 7 from 1 showed between 85–95% yields.
works have been reported.
When propargylamine and its
After obtaining quantitative information regarding the abil- derivatives bearing alkyl or phenyl groups 8 were added to a
ity of MEA 1 to absorb CO , our efforts shifted from the ab- Au or Ag catalyst in MeOH under atmospheric conditions, no
2

Vol. 64, No. 1 (2016)
Chem. Pharm. Bull.
11
Fig. 4. CO Generator Provides Energyless Recycling of Atmospheric CO2
2
a) MEA 1 that had absorbed atmospheric CO2 for at least 1.5d to provide (CO )·3(MEA)·3(H O) 7 released CO after the addition of 10% HCl. b) The experimental
2
2
2
setup for CO2 generation and reaction. The CO2 liberated by the addition of 10% HCl to (CO )·3(MEA)·3(H O)7ꢀisꢀrapidlyꢀreleased,ꢀwhichꢀisꢀthenꢀableꢀtoꢀbeꢀfixedꢀusingꢀaꢀ
2
2
reaction that consumes CO . c) All reactions were examined using CO2 generator. The catalysts used in this study include catalyst A: Au(Xantphos)Cl, B: [Au(JohnPhos)-
2
(
NCMe)]SbF , C: Au(IPr)Cl, D: AgSbF , and E: AgOAc. These catalysts were independently selected after pre-examination using catalysts A–E or combination of A+D,
6
6
A+E, C+D, C+E.
desired product 9 was observed (Fig. 3, Eq. 1). The addition yields; these results were dependent on uncontrollable vari-
of MEA 1 or (CO )·3(MEA)·3(H O) 7 also failed to produce ables of the environment rather than the reactants (Eq. 3). The
2
2
9. These results suggested that the carboxylation of the amine addition of the N-hydroxyethyl group was necessary to ob-
to carbamic acid requires activation or high CO concentra- serve metal-catalysed urethanation in this study. However, its
2
tions. Thus, we prepared N-hydroxyethyl propargylamine reactivity was highly affected by variable CO concentrations
2
(
HEPA) 10. Because MEA 1 absorbs atmospheric CO , the and other atmospheric variables.
2
N-hydroxyethyl group of HEPA 10 should assist in the absorp-
Based on the reactions shown in Fig. 3, we inferred that
tion of CO , and intramolecular cyclization can occur more moreꢀ effectiveꢀ fixationꢀ wouldꢀ requireꢀ higherꢀ andꢀ moreꢀ
2
easily via an intermediate 10′. Indeed, the incubation of HEPA stable CO concentrations. During several experiments using
2
1
0 and 2mol% Au(Xantphos)Cl in MeOH at ambient tem- (CO )·3(MEA)·3(H O) 7, we found that the addition of 10%
2 2
5
0)
perature provided the desired product 11 (Eq. 2). Notably, HCl effectively liberated gaseous CO at room temperature
2
a lack of reproducibility regarding yields (2–20%) occurred, (Fig. 4a). The formation of ammonium ions may prompt
which is presumably due to variations in the CO concentra- CO2 disassociation. Thus, we devised a new CO2 genera-
2
tion (300–700ppm) in the studied air. No improvements were tor using atmospheric CO . The system is shown in Fig. 4b.
2
observed when additional MEA 1 or (CO )·3(MEA)·3(H O) The generation of gaseous CO2 by adding 10% HCl to
2
2
7
was added. Although other derivatives of 12 that contained (CO )·3(MEA)·3(H O) 7ꢀinꢀaꢀclosedꢀflaskꢀenabledꢀusꢀtoꢀcreateꢀ
2 2
1
2
an alkyl or phenyl group (R ) or hydroxyethyl group (R ) at an environment for the reaction with high CO levels. Using
2
the alkyne terminus provided the product 13 with up to 41% this improved technique, the reaction of HEPA 10 (2mol%

1
2
Chem. Pharm. Bull.
Vol. 64, No. 1 (2016)
4
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Menne M. J., Peterson T. C., Vose R. S., Zhang H.-M., Science, 348,
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good yield (73%) (Fig. 4c, entry 1). Moreover, the other select-
ed substrates 12a–g, which incorporated various substituents,
produced the desired products 13a–g with acceptable yields
and reliable reproducibilities (entries 2–9). We further demon-
strated that the intramolecular assistance of the hydroxyethyl
group in these substrates was not essential. Using propargyl-
amine (8a) or other derivatives (8b–d, i.e., no hydroxylethyl
groups) provided the carboxylated products 9a–d with high
yields (entries 10–14). Notably, such reactions do not require
1
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2
and catalyst in MeOH by shaking by hand for several seconds,
the reaction of 12a provided the product 13a with a compara-
ble yield (72%, entry 3). Similar results were observed for the
reaction of 8aꢀ(85%ꢀyield,ꢀentryꢀ11).ꢀThus,ꢀfixationꢀproceededꢀ
without external energy inputs.
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(
mospheric CO regardless of the ambient sunlight conditions
2
1
2
and without external energy inputs in the form of heating,
cooling, or stirring. We also developed CO ꢀfixationꢀreactionsꢀ
2
using oxazolidinone derivatives. An N-hydroxyethyl moiety
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the methods described herein will provide an alternative to
2
2
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2
2
3
Further improvements (e.g., recycling of MEA) and applica-
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2
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Acknowledgment We are grateful for the support of
Grant-in-Aidꢀ forꢀ Scientificꢀ Researchꢀ fromꢀ theꢀ Ministryꢀ ofꢀ
Education, Culture, Sports, Science and Technology of Japan.
8
3
(
3
5) Williams C. M., Johnson J. B., Rovis T., J. Am. Chem. Soc., 130,
Conflict of Interest Theꢀ authorsꢀ declareꢀ noꢀ conflictꢀ ofꢀ
interest.
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3
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2