A mild hydrothermal route to fix carbon dioxide to simple carboxylic acids

Article abstract of DOI:10.1021/ol9025414

CO₂+H₂O cat. iron nano-partices → hydrothermal condition HCOOH+CH₃COOH The reduction of carbon dioxide (CO ₂) under mild hydrothermal conditions was carried out in the presence of iron nanoparticles. In this reaction system, the iron nanopartlcles not only act as the reducing agent but also catalyze the reduction of CO₂ to form formic acid and acetic acid.

Full text of DOI:10.1021/ol9025414

ORGANIC
LETTERS
2010
Vol. 12, No. 4
649-651
A Mild Hydrothermal Route to Fix
Carbon Dioxide to Simple Carboxylic
Acids
Chao He, Ge Tian, Ziwei Liu, and Shouhua Feng*
State Key Laboratory of Inorganic Synthesis and PreparatiVe Chemistry, College of
Chemistry, Jilin UniVersity, Changchun 130021, P. R. China
shfeng@mail.jlu.edu.cn
Received November 3, 2009
ABSTRACT
The reduction of carbon dioxide (CO2) under mild hydrothermal conditions was carried out in the presence of iron nanoparticles. In this
reaction system, the iron nanoparticles not only act as the reducing agent but also catalyze the reduction of CO2 to form formic acid and
acetic acid.
According to the Intergovernmental Panel on Climate Change
(IPCC 2007),1 the Earth’s surface temperature has risen by
approximately 0.74 K from 1906 to 2006. The primary
contributor to this phenomenon is CO2 emission from fossil
fuel combustion. Presently, the concentration of CO2, which
is the most important anthropogenic greenhouse gas, is
increasing faster than at any other time. A great deal of effort
has been expended to reduce the concentration of CO2,
among which the chemical reduction of CO2 to organic
compounds is considered as one of the most expected
solutions for the “Greenhouse Effect” problem.2 CO2 can
be transformed from a detrimental greenhouse gas into a
valuable, inexhaustible, and eco-friendly carbon source
through this process. Many methods to reduce CO2 have been
carried out, such as the catalytic hydrogenation reduction,3
Fischer-Tropsch synthesis,4 photochemical reduction,5 elec-
trochemical reduction,6 and photoelectrochemical reduction,7
etc. Because of the poor yields, high cost, or rigorous reaction
conditions, the results are still not satisfactory.
The reduction of CO2 under hydrothermal conditions8 has
attracted more attention in these decades. On one hand, it
may be a feasible program to solve the “Greenhouse Effect”
problem; on the other hand, it has a plausible implication
for the abiotic synthesis of complex organic molecules in
the origin of life because the hydrothermal system is
considered to be one of the most optimal environments for
the origin of life.9,10 It is reported that nickel-iron alloy
-
can catalyze dissolved HCO3 with H2 to form CH4 under
hydrothermal conditions (200 to 400 °C and 50 MPa).8a
Formic acid could also be generated in the process of
hydrothermal reduction of CO2 at the effect of Ni-powder
(6) Vladimirov, M. G.; Ryzhkov, Y. F.; Alekseev, V. A.; Bogdanovskaya,
V. A.; Otroshchenko, V. A.; Kritsky, M. S. Origins Life EVol. Biospheres
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2007: The Physical Science Basis; Cambridge University Press: New York,
U.S.A., 2007.
(7) (a) Zhang, X. V.; Martin, S. T.; Friend, C. M.; Schoonen, M. A. A.;
Holland, H. D. J. Am. Chem. Soc. 2004, 126, 11247. (b) Barton, E. E.;
Rampulla, D. M.; Bocarsly, A. B. J. Am. Chem. Soc. 2008, 130, 6342.
(8) (a) Horita, J.; Berndt, M. E. Science 1999, 285, 1055. (b) Takahashi,
H.; Kori, T.; Onoki, T.; Tohji, K.; Yamasaki, N. J. Mater. Sci. 2008, 43,
2487. (c) Takahashi, H.; Liu, L. H.; Yashiro, Y.; Ioku, K.; Bignall, G.;
Yamasaki, N. J. Mater. Sci. 2006, 41, 1585. (d) Tian, G.; Yuan, H.; Mu,
Y.; He, C.; Feng, S. Org. Lett. 2007, 9, 2019.
(2) Olah, G. A.; Goeppert, A.; Prakash, G. K. S. J. Org. Chem. 2009,
74, 487.
(3) (a) Yu, K. M. K.; Yeung, C. M. Y.; Tsang, S. C. J. Am. Chem. Soc.
2007, 129, 6360. (b) An, X.; Li, J.; Zuo, Y.; Zhang, Q.; Wang, D.; Wang,
J. Catal. Lett. 2007, 118, 264. (c) Gao, L. Z.; Au, C. T. J. Catal. 2000,
189, 1. (d) Chan, B.; Radom, L. J. Am. Chem. Soc. 2006, 128, 5322.
(4) Pe´rez-Alonso, F. J.; Ojeda, M.; Herranz, T.; Rojas, S.; Gonza´lez-
Carballo, J. M.; Terreros, P.; Fierro, J. L. G. Catal. Commun. 2008, 9, 1945.
(5) (a) Usubharatana, P.; McMartin, D.; Veawab, A.; Tontiwachwuthikul,
P. Ind. Eng. Chem. Res. 2006, 45, 2558. (b) Koci, K.; Obalova, L.; Lacny,
Z. Chem. Pap. 2008, 62, 1. (c) Xia, X. H.; Jia, Z. J.; Yu, Y.; Liang, Y.;
Wang, Z.; Ma, L. L. Carbon 2007, 45, 717.
(9) Corliss, J. B.; Dymond, J.; Gordon, L. I.; Edmond, J. M.; von Herzen,
R. P.; Ballard, R. D.; Green, K.; Williams, D.; Bainbridge, A.; Crane, K.;
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10.1021/ol9025414  2010 American Chemical Society
Published on Web 01/27/2010

and Fe-powder.8b,c Since Fe is abundant and widespread,
which accounts for 5.0 wt % of the Earth’s crust, it is used
as catalyst widely in the reduction of CO2, and it could have
played an important role in prebiotic synthesis. In our
previous work, we also used Fe as catalyst to synthesize
phenol from the hydrothermal reaction of carbonate with
water.8d Our group has concentrated tremendous efforts on
the reduction of CO2 under hydrothermal conditions. Herein,
we described a mild hydrothermal route from CO2 to simple
carboxylic acids in the presence of iron nanoparticles.
The reactions of CO2 with water in the presence of iron
nanoparticles were carried out using the Endeavor Catalyst
Screening System (Argonaut Technologies, Inc.). Iron nano-
particles were prepared by reducing ferrous ion (Supporting
Information). The result of gas chromatography-mass spec-
troscopy (GC-MS) indicated that CO2 (99.999%) and
ultrapure water were free of any organic contamination. We
put the iron nanoparticles and ultrapure water into a reactor,
sealed it, and then pressurized it to 0.14-1.4 MPa by CO2
gas. The mixture was subjected to a hydrothermal treatment
at 80-200 °C for 5-200 h. After the reaction, the pH value
of the mixture was 5.5. The product was identified by
GC-MS.
Figure 2. Yields of formic acid and acetic acid at different
temperatures. Water: 6 mL. CO2: 1.4 MPa. Fe: 5 mmol. Reaction
time: 72 h.
acetic acid increases less. The total conversion of CO2 increases
as the temperature increases. We think that at higher temperature
H2 is produced more and faster, which provides a stronger
reducing environment and promotes the conversion of CO2.
Higher CO2 pressure can increase the yield of formic acid
because more CO2 is adsorbed and a more active center is
formed at the surface of the iron nanoparticles. The volume
of water has little effect on the conversion of CO2.
It is quite evident that formic acid and acetic acid were
formed after the hydrothermal reduction of CO2, when the
mass spectra of the products were compared to that of
standard substance (Supporting Information, Figures S1 and
S2). As shown in Figure 1, the yields of formic acid and
On the basis of the result of the reaction, we proposed a
possible reaction mechanism of formic acid and acetic acid
formation. Scheme 1 illustrates the main process of the reaction
Scheme 1. Proposed Mechanism for the Formation of Formic
Acid and Acetic Acid in the Presence of Nano Fe under
Hydrothermal Conditions
Figure 1. Kinetic curve of the hydrothermal production of formic
acid (A) and acetic acid (B). Water: 6 mL. CO2: 1.4 MPa. Fe: 5
mmol. Temperature: 200 °C.
acetic acid increase with the increase of reaction time,
reaching the maximum value after 72 h, and then remain
nearly constant. The yields of formic acid and acetic acid
are 8.5 and 3.5 mmol·L-1, respectively.
The effect of temperature was also taken into account. As
shown in Figure 2, the yield of formic acid increases
obviously with the increase of temperature, while the yield of
650
Org. Lett., Vol. 12, No. 4, 2010

(see details in Supporting Information, Scheme S1). At the first
stage of the reactions, the iron nanoparticles reacted with water,
producing H2. Meanwhile, the dissolved CO2 molecule was
adsorbed at the surface of the iron nanoparticles. At the attack
of H2, CO2 was reduced to intermediate A, which was
hydrolyzed to formic acid. Intermediate A continued reacting
with H2, generating intermediate B. At last, intermediate A and
intermediate B reacted to form intermediate C, which was
hydrolyzed to acetic acid.
In the reaction system, the iron nanoparticles not only act
as a reducing agent but also catalyze the reduction of CO2.
As shown in Figure 3, the diameter of the particles was about
Figure 4. XRD pattern of the residual solid after removal of
unreacted iron by a magnet.
an active reaction center, which was reduced by H2 to form
formic acid and acetic acid under this environment.
Compared to other reported methods of the reduction of
CO2, the characteristics of this reaction system are as follows:
first, the catalyst, Fe powder, is widespread and prepared
readily. Second, the reaction is carried out under lower
pressure and temperature, which is readily accessible. Third,
we do not need to add additional H2 as reducing agent to
the reaction system because H2 is autogenously generated
in the reaction. Fourth, water as the source of hydrogen is
necessary in this reaction, and it does not impede the
formation of the organic matter.
Figure 3. Low-magnification scanning electron microscopy (SEM)
images of the prepared iron nanoparticles.
In summary, we demonstrate a mild hydrothermal route
for reducing CO2 to formic acid and acetic acid with the
catalytic effect of iron nanoparticles. The present work is a
basic study for CO2 fixation, and it will provide a possible
way to reduce the concentration of CO2 and to mitigate the
“Greenhouse effect” after further research.
200 nms. The highly active iron nanoparticles reacted rapidly
with water to form H2, whose formation was confirmed by
igniting. After the reaction, the unreacted iron was separated
by magnet, and the residual solid was collected and then
checked by powder X-ray diffraction (XRD). The result of
XRD showed that the solid was ferrous carbonate (Figure
4). It is concluded that a great part of the iron nanoparticles
was converted to ferrous carbonate after the hydrothermal
reaction. The production of H2 and ferrous carbonate also
confirmed the suggested mechanism.
Acknowledgment. This work was supported by the
National Natural Science Foundation of China (No. 20631010
and 90922034).
Supporting Information Available: Experimental pro-
cedure, the preparation method of the catalyst, GC-MS
characterization, calibration curves of formic acid and acetic
acid for GC-MS and method of calculation for the yields,
and detailed mechanism for the formation of formic acid and
acetic acid. This material is available free of charge via the
Internet at http://pubs.acs.org.
The products of this reaction are formic acid and acetic
acid instead of phenol obtained in our previous work.8d We
think the amount of rapid formation of H2 plays an important
role in the selectivity of the product. At the beginning of
the reaction, more H2 was generated from the reaction of
the iron nanoparticles with water than from the reaction
of iron powder with water, which provided a stronger
reducing environment. Each adsorbed CO2 molecule formed
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