Highly selective hydrogenation of CO2 into C2+ alcohols by homogeneous catalysis

Article abstract of DOI:10.1039/c5sc02000j

The hydrogenation of CO₂ to produce alcohols with two or more carbons (C₂₊ alcohols) is of great importance, but is challenging. In this work, we found that a Ru₃(CO)₁₂/Rh₂(CO)₄Cl₂-LiI system could catalyze the reaction effectively in 1,3-dimethyl-2-imidazolidinone (DMI) under mild conditions. Methanol, ethanol, propanol, 2-methyl propanol, butanol, and 2-methyl butanol were produced in the homogeneous catalytic reaction. The C₂₊ alcohols could be generated at 160 °C, which is the lowest temperature reported so far for producing C₂₊ alcohols via CO₂ hydrogenation. The selectivity for the C₂₊ alcohols could be as high as 96.4% at the optimized conditions, which is higher than those reported in the literature. In addition, the catalytic system could be easily recycled. The route of the reaction for forming the C₂₊ alcohols was discussed on the basis of control experiments.

Full text of DOI:10.1039/c5sc02000j

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Highly selective hydrogenation of CO2 into C2+
alcohols by homogeneous catalysis†
Cite this: DOI: 10.1039/c5sc02000j
*
Qingli Qian, Meng Cui, Zhenhong He, Congyi Wu, Qinggong Zhu, Zhaofu Zhang,
*
Jun Ma, Guanying Yang, Jingjing Zhang and Buxing Han
The hydrogenation of CO2 to produce alcohols with two or more carbons (C2+ alcohols) is of great
importance, but is challenging. In this work, we found that a Ru3(CO)12/Rh2(CO)4Cl2–LiI system could
catalyze the reaction effectively in 1,3-dimethyl-2-imidazolidinone (DMI) under mild conditions.
Methanol, ethanol, propanol, 2-methyl propanol, butanol, and 2-methyl butanol were produced in the
homogeneous catalytic reaction. The C2+ alcohols could be generated at 160 ꢀC, which is the lowest
temperature reported so far for producing C2+ alcohols via CO2 hydrogenation. The selectivity for the
C2+ alcohols could be as high as 96.4% at the optimized conditions, which is higher than those reported
in the literature. In addition, the catalytic system could be easily recycled. The route of the reaction for
forming the C2+ alcohols was discussed on the basis of control experiments.
Received 4th June 2015
Accepted 29th June 2015
DOI: 10.1039/c5sc02000j
www.rsc.org/chemicalscience
alcohol was ethanol and the highest selectivity of C2+ alcohols in
the alcohols was about 70%.6 Kurakata et al.7 reported that
Introduction
[Rh10Se]/TiO2 could promote the hydrogenation of CO2 to
produce ethanol at temperatures from 250 to 450 C, and the
Carbon dioxide (CO2) is a renewable, abundant, and cheap C1
feedstock.1 The use of CO2 as a carbon source to produce fuels
and value-added chemicals is of great importance for the
sustainable development of our society. The transformation of
CO2 into various compounds, such as urea, salicylic acid,
carbonates, polymers, alcohols, and formic acid, has been
studied extensively.2
ꢀ
highest ethanol selectivity was 83%. Nieskens et al.8 fabricated a
CoMoS based catalyst for synthesizing C1–C3 alcohols via CO2
hydrogenation at 340 ꢀC, and the highest C2+ alcohol content in
the alcohol mixture was 35.6%. Li et al.9 prepared a K/Cu–Zn–Fe
catalyst, which was used in the reaction at 300 ꢀC. The selectivity
to C2+ alcohols reached 87.1%. Tominaga et al.16 reported CO2
hydrogenation using a Ru–Co homogeneous catalyst at 200 ꢀC,
and only methanol and ethanol were formed, with an ethanol
selectivity of 26.4% in the alcohol products.
The hydrogenation of CO2 to produce alcohols is one of the
most important routes for converting CO2, which has received
much attention, especially for producing methanol.3 In many
cases, ethanol and larger alcohols (C2+ alcohols hereaer) are
more desirable products, as neat fuels, fuel additives, and
chemicals, than methanol.4 However, producing C2+ alcohols by
CO2 hydrogenation is more difficult than producing methanol.
Up to now, heterogeneous catalysts have been designed and
used in the synthesis of C2+ alcohols by the catalytic hydroge-
nation of CO2, and some excellent results have been
obtained.5–15 For example, it was found that alkali-promoted
Mo/SiO2 catalystꢀs could catalyze CO2 hydrogenation to form C2+
alcohols at 250 C. The content of C2+ alcohols in the alcohol
mixture could be 75.6%.5 Supported Rh, Fe-based, and Cu-
based catalysts were combined for the synthesis of C2+ alcohols,
and the multi-functional heterogeneous catalysts could
As discussed above, the synthesis of C2+ alcohols by the
hydrogenation of CO2 has received considerable attention.
However, in general, the heterogeneous catalysts suffer from
low activity, low C2+ alcohol selectivity, and high reaction
temperature. There is no doubt that exploration of the routes for
highly selective CO2 hydrogenation to produce C2+ alcohols
under relatively mild conditions is of great importance. In this
work, we studied the hydrogenation of CO2 into C1–5 alcohols
catalyzed by a Ru–Rh bimetallic homogeneous catalyst using LiI
as the promoter (Scheme 1).
It was found that the catalytic system could catalyze the
reaction effectively under mild conditions. The liquid products
ꢀ
promote the reaction effectively at 330–370 C. The major C2+
Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Colloid,
Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy
of Sciences, Beijing 100190, China. E-mail: qianql@iccas.ac.cn; hanbx@iccas.ac.cn;
Tel: +86-10-62562821
† Electronic supplementary information (ESI) available: Supplementary gures
and tables. See DOI: 10.1039/c5sc02000j
Scheme 1 Synthesis of C2+ alcohols from CO2 hydrogenation.
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were mainly methanol, ethanol, propanol, 2-methyl propanol, but the selectivity to C2+ alcohols was very low (Entry 3). The
butanol and 2-methyl butanol, including both linear and results show that the promoter affected the activity, selectivity,
branched alcohols. The products were distinct from those and stability of the catalyst. The superiority of LiI in promoting
generated via homogeneous CO2 or CO hydrogenation reported the synthesis of C2+ alcohols may be partly attributed to the
in the literature. The alcohols could be generated at 160 ꢀC. The stronger Lewis acidity of the lithium cation, which could offer
selectivity for C2+ alcohols could be as high as 96.4% at the suitable coordination sites during the catalytic reaction. The
optimized conditions. In addition, the catalytic system could be anionic counterpart of the promoter also evidently inuenced
recycled and reused.
the catalytic performance. When LiCl was used, the selectivity
for C2+ alcohols was much lower (Entry 4). The better perfor-
mance of the iodide anion may be ascribed to its stronger
nucleophilicity, which would promote the chain growth
reaction.
Results and discussion
Different catalytic systems were tested for the reaction, and the
results are listed in Table 1. The corresponding selectivities for
the different alcohols are shown in detail in Table S1.† When
LiI was used as the promoter and 1,3-dimethyl-2-imidazolidi-
We also used Ru3(CO)12 (Entry 5) and Rh2(CO)4Cl2 (Entry 6)
separately, but the yield of the product and the selectivity to the
C
2+ alcohols was very low, indicating the synergistic effect of the
two catalysts in accelerating the reaction. Thus we choose the
space time yield (STY) to express the catalytic activity, which
may give an integrated evaluation of the bimetallic catalytic
system. The reaction was also carried out in other solvents, and
it was demonstrated that DMI was the best solvent for the
reaction (Entries 1 and 7–12). One of the main reasons is that
the catalyst was stable in DMI, but it was not stable in most of
the other solvents used. In N-methyl-2-pyrrolidone (NMP), the
catalyst was also stable, but the efficiency of the reaction was
lower than that in DMI. This indicates that the solvent effect is
also important for the reaction. Using LiI as the promoter and
DMI as the solvent, the performance of other mixed catalysts,
such as RuCl3$3H2O/Rh2(CO)4Cl2, Ru3(CO)12/RhCl3$xH2O, and
Ru3(CO)12/Rh6(CO)16, were also studied (Entries 13–15), but the
efficiencies were lower than that of Ru3(CO)12/Rh2(CO)4Cl2
because of their poor stability. The results above indicate that
the catalytic system composed of Ru3(CO)12/Rh2(CO)4Cl2, LiI,
and DMI had good activity, selectivity, and stability for the
hydrogenation of CO2 to generate C2+ alcohols. Therefore, the
effects of the reaction conditions were further studied using this
catalytic system.
none (DMI) as the solvent, the combined catalyst Ru3(CO)12
/
Rh2(CO)4Cl2 could catalyze the hydrogenation of CO2 very
effectively, with methanol, ethanol, propanol, 2-methyl prop-
anol, butanol, and 2-methyl butanol as the products, and other
products being negligible in the reaction solution (Fig. S1†).
The alcohol products, including both linear and branched
C1–C5 alcohols, are different from those obtained via CO
hydrogenation using Ru and/or Rh catalysts, since they give
largely linear hydrocarbons over heterogeneous catalysts, and
produce only C1 and C2 oxygenates in homogeneous catal-
ysis.17 Very interestingly, the selectivity for C2+ alcohols could
be as high as 96.4% (Entry 1), which is much higher than those
reported in the literature.
The promoter LiI played an important role in accelerating
the reaction. Without the promoter, a little amount of methanol
was generated, and the amount of the C2+ alcohols was negli-
gible (Entry 2). In the presence of LiI, the reaction solution was
clear aer reaction, but black ne metal powder was found
when LiI was not added, indicating that LiI could stabilize the
catalyst. When LiI was replaced by KI, the catalyst was also
stable at the reaction conditions with a high yield of methanol,
Table 1 The performances of various catalytic systems for CO2 hydrogenation to C2+ alcoholsa
Entry
Catalyst
Promoter
Solvent
STYc of alcohols
C2+OH%
1
Ru3(CO)12, Rh2(CO)4Cl2
Ru3(CO)12, Rh2(CO)4Cl2
Ru3(CO)12, Rh2(CO)4Cl2
Ru3(CO)12, Rh2(CO)4Cl2
Ru3(CO)12
LiI
—
KI
DMI
DMI
DMI
DMI
DMI
DMI
12.86
0.36
14.36
16.17
2.43
1.07
5.11
2.07
7.64
0.0
96.4
2.8
8.3
17.7
0.4
2.9
72.4
0.0
0.0
—
2b
3
4
LiCl
LiI
LiI
LiI
LiI
LiI
LiI
LiI
LiI
LiI
LiI
LiI
5
6b
7
Rh2(CO)4Cl2
Ru3(CO)12, Rh2(CO)4Cl2
Ru3(CO)12, Rh2(CO)4Cl2
Ru3(CO)12, Rh2(CO)4Cl2
Ru3(CO)12, Rh2(CO)4Cl2
Ru3(CO)12, Rh2(CO)4Cl2
Ru3(CO)12, Rh2(CO)4Cl2
RuCl3$3H2O, Rh2(CO)4Cl2
Ru3(CO)12, RhCl3$xH2O
Ru3(CO)12, Rh6(CO)16
NMP
1-Methyl piperidine
DMF
THF
Cyclohexane
Water
DMI
DMI
DMI
8b
9b
10b
11b
12b
13b
14b
15b
0.0
—
1.45
2.73
3.38
3.40
6.5
7.4
5.7
25.4
a
Reaction conditions: 28.2 mmol Ru catalyst and 51.5 mmol Rh catalyst (based on the metal), 2.26 mmol promoter, 2 mL solvent, 4 MPa CO2 and 4
MPa H2 (at room temperature), 200 ꢀC and 12 h. b Precipitate was observed aer the reaction. c STY stands for space time yield (C mmol LÀ1 hÀ1),
which is one of the commonly used units, especially when multi-metals are utilized.
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Fig. 1 depicts the results of the CO2 hydrogenation con- amount of the alcohols generated decreased slightly but the C2+
ducted at different temperatures. At 150 ꢀC, only methanol and alcohols selectivity increased greatly. However, as the dosage
ethanol were formed, and methanol was the major product. further increased to 3.39 mmol, the selectivity to C2+ alcohols
ꢀ
When the temperature reached 160 C, the yields of methanol remained high, but the total yield of the alcohols reduced
and ethanol increased, and C3+ alcohols emerged. Thus, 160 ꢀC considerably. The main reason may be that more active sites
was the initial temperature for the obvious formation of C3+ were occupied by iodide anions as an excess amount of LiI was
alcohols. So far this is the lowest temperature reported for the used, inhibiting the hydrogenation reaction. The atomic ratio of
formation of these alcohols. The yields of all the alcohols Ru and Rh also affected the yield of the reaction. At the same
increased as the temperature rose. From 180 to 200 ꢀC, the total amount of Ru and Rh (79.7 mmol), 28.2 mmol Ru and 51.5
methanol yield underwent a dramatic drop, accompanied with mmol Rh gave the highest total yield of the alcohols and the
an evident increase in the yields of the target C2+ alcohols. In the selectivity for C2+ alcohols (Entries 5 and 6 of Table 1, Entries 4,
ꢀ
range of 200–220 C, the yields of methanol and ethanol were 10, 11, 12 of Table 2). As expected, the total yield of the alcohols
nearly unchanged with increasing temperature, but the yields of increased with an increasing amount of the catalyst (Entries 4,
the other alcohols increased continuously with increasing 13, 14, 15), but the yield was less sensitive to the amount of
temperature. The main reason is that the methanol formed can catalyst as the amount was large enough.
be further transformed into ethanol, and the ethanol can be
We carried out experiments on the reuse of the catalytic
converted into larger alcohols, which will be discussed in more system. Aer reaction, the alcohols generated in the reaction
detail in the following paragraphs. The yield of methanol is were removed under vacuum, which was conrmed by GC
much lower than that of ethanol in this temperature range analysis. Then the catalyst, solvent (DMI), and the LiI were used
because methanol is more reactive than ethanol. Therefore, the directly for the next run. The results of the reuse experiments
methanol generated was converted into ethanol quickly.
are given in Table S3.† The yield of the total alcohols and the
The results in Fig. 1 suggest that 200 ꢀC is a suitable selectivity to C2+ alcohols did not change obviously aer ve
temperature. We further studied the effects of other parameters cycles (12 h each cycle), indicating that the catalyst was stable
on the reaction at this temperature, and the results are given in for at least 60 h at this temperature.
Table 2. The corresponding selectivities to different alcohols are
Fig. 2 presents the time course for the formation of the
shown in Table S2.† The C2–C5 alcohols were generated at all alcohols. Methanol, ethanol and propanol were generated
the conditions. At a xed pressure ratio of CO2 and H2 (1 : 1), within 1 h and their yields increased with time. Aer 6 h, a
the total yield of the alcohols and the selectivity to the C2+ considerable amount of 2-methyl propanol, butanol, and 2-
alcohols increased remarkably as the total pressure was raised methyl butanol could be detected and their amounts increased
from 2 MPa to 10 MPa (Entries 1–5). At the same pressure, the with time. The methanol content began to decrease quickly and
total yield of the alcohols increased with the partial pressure of the amounts of the higher alcohols increased continuously with
H2 (Entries 4, 6, 7), but the selectivity to C2+ alcohols was highest the reaction proceeding. Aer 12 h, the methanol content was
at a CO2 : H2 pressure ratio of 1 : 1. The dosage of LiI was crucial low and did not change considerably with time. At the same
for the alcohols generation (Entry 2 of Table 1, Entries 4, 8, and time, the ethanol content began to decrease slowly, and the
9 of Table 2). When the LiI dosage was in the range of 0–1.13 content of the C3+ alcohols continued to increase with reaction
mmol, both the total yield of the alcohols and the selectivity to time. The yield of methanol passed through a maximum with
C2+ alcohols increased signicantly with the increase in the increasing reaction time. With the increase of reaction time,
dosage. As the LiI dosage was increased to 2.26 mmol, the some of the methanol is transformed into ethanol and the
ethanol can be further converted, and so on.
The results above suggest that methanol was formed from
CO2 and H2 in the reaction. The methanol acts as the inter-
mediate for the generation of ethanol, and the ethanol can be
converted into larger alcohols in the reaction process. In order
to obtain more evidence to support this argument, we carried
out tracer experiments by adding small amounts of 13CH3OH or
13C2H5OH in the reaction system at 200 ꢀC with a reaction time
of 12 h. The GC-MS results with 13CH3OH and 13C2H5OH are
shown in Fig. S2 and S3,† respectively. When 13CH3OH was used
as the tracer, C2+ alcohols containing 13C were yielded. Simi-
larly, when the 13C2H5OH tracer was added in the reaction
system, 13C was present in some C3+ alcohols. Therefore, it can
be concluded that in the hydrogenation of CO2 for obtaining the
alcohols, the methanol and ethanol formed act as intermediates
for forming the larger alcohols.
Fig.
1 The space time yields (STY) of the alcohols at different
Only methanol and ethanol were produced as alcohol
products in the homogeneous CO2 hydrogenation.16 It was also
reported that only C1 and C2 oxygenates were yielded via CO
temperatures. Reaction conditions: 28.2 mmol Ru3(CO)12 and 51.5
mmol Rh2(CO)4Cl2 (based on the metal), 2.26 mmol LiI, 2 mL DMI, 4
MPa CO2 and 4 MPa H2 (at room temperature), and 12 h.
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Table 2 Effect of reaction parameters on hydrogenation of CO2 to alcoholsa
Entry
Ru/Rh [mmol]
LiI [mmol]
CO2/H2 [MPa]
STY of alcohols
C2+ [%]
1
2
3
4
5
6
7
8
28.2/51.5
28.2/51.5
28.2/51.5
28.2/51.5
28.2/51.5
28.2/51.5
28.2/51.5
28.2/51.5
28.2/51.5
8.0/71.7
39.9/39.9
55.8/23.9
0/0
2.26
2.26
2.26
2.26
2.26
2.26
2.26
1.13
3.39
2.26
2.26
2.26
2.26
2.26
2.26
1/1
2/2
3/3
4/4
5/5
2/6
6/2
4/4
4/4
4/4
4/4
4/4
4/4
4/4
4/4
1.13
3.39
5.37
12.86
14.10
20.66
3.17
14.25
5.88
3.32
12.07
8.57
0
77.0
90.6
92.6
96.4
96.1
39.0
84.2
40.6
97.1
84.0
76.9
80.4
—
9
10
11
12
13
14
15
14.1/25.8
42.3/77.3
4.48
16.31
47.8
93.9
a
Reaction conditions: Ru3(CO)12/Rh2(CO)4Cl2 were used as the catalysts and their dosage was based on the metal, LiI was used as the promoter, 2
mL DMI, 200 ꢀC, and 12 h.
catalytic system can be reused. In the reaction, methanol is rst
formed, and the small alcohol can act as the intermediate for
generating the larger ones. The C2+ alcohols include both linear
and branched alcohols, which is distinct from those produced
via homogeneous CO2 or CO hydrogenation reported in the
literature. We believe that many other catalytic systems can be
explored for the hydrogenation of CO2 by combination of
various homogeneous catalysts, co-catalysts, and solvents.
Experimental
Chemicals
Ruthenium carbonyl (Ru3(CO)12, purity > 98%) was purchased
from Adamas Reagent, Ltd. Tetracarbonyl-di-m-chlor-
odirhodium(I) (Rh2(CO)4Cl2, Rh 50.1–52.9%), rhodium(III)
chloride hydrate (RhCl3$xH2O, Rh 38.5–45.5%), anhydrous
lithium iodide (LiI, 99.95%), potassium iodide, (KI, 99.9%), and
1-methyl piperidine (99%) were obtained from Alfa Aesar China
Co., Ltd. Hexarhodiumhexadecacarbonyl (Rh6(CO)16, 98%) was
provided by J&K Chemical Ltd. (Shanghai). Ruthenium(III)
chloride hydrate (RuCl3$3H2O, Ru 36.7%) was provided by
Shenyang Jinke Reagent Co., Ltd. 1,3-Dimethyl-2-imidazolidi-
none (DMI, 99%) was purchased from TCI Shanghai Co., Ltd. N-
Methyl-2-pyrrolidone (NMP, 99.5%), N,N-dimethylformamide
(DMF, 99.5%) and cyclohexane (99.5%) were provided by Sino-
pharm Chemical Reagent Co., Ltd. Tetrahydrofuran (THF, A.R.
Grade) was obtained from Beijing Chemical Company. Toluene
(99.8%, HPLC) was obtained from Xilong Chemical Co., Ltd.
Methanol-13C (99 atom% 13C) and ethanol-13C2 (99 atom% 13C)
were purchased from Sigma-Aldrich Co. LLC. The CO2 (99.99%)
and H2 (99.99%) were provided by Beijing Analytical Instrument
Company.
Fig. 2 Time course of the alcohol formation. Reaction conditions:
28.2 mmol Ru3(CO)12 and 51.5 mmol Rh2(CO)4Cl2 (based on the metal),
2.26 mmol LiI, 2 mL DMI, 4 MPa CO2 and 4 MPa H2 (at room
temperature), and 200 ꢀC.
hydrogenation using homogeneous Ru and/or Rh catalysts.17,18
Whereas the alcohols generated by our catalytic system
included C1–C5 alcohols of both linear and branched structures.
This suggests that the reaction pathway of CO2 hydrogenation
using our catalytic system is obviously different from those of
the CO2 or CO hydrogenation reported in the literature.16–18
Conclusions
In summary, we have studied the performance of different
catalysts, promoters, and solvents for the synthesis of C2+
alcohols by the hydrogenation of CO2. It is discovered that
Ru3(CO)12, Rh2(CO)4Cl2, and LiI exhibit an excellent synergistic
effect in catalyzing the reaction using DMI as the solvent. The
Ru3(CO)12/Rh2(CO)4Cl2/LiI-DMI homogeneous catalytic system
can catalyze the reaction effectively and selectively at relatively
Hydrogenation of CO2
mild conditions. The target C2+ alcohols start to form at 160 ꢀC. All the reactions were conducted in a 16 mL Teon-lined
The selectivity to the C2+ alcohols can reach 96.4%, and the stainless steel reactor equipped with a magnetic stirrer. In a
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typical experiment, known amounts of the Ru and/or Rh cata-
2931; (j) Y. Y. Zhang, A. D. MacIntosh, J. L. Wong,
E. A. Bielinski, P. G. Williard, B. Q. Mercado, N. Hazari and
W. H. Bernskoetter, Chem. Sci., 2015, 6, 4291–4299.
3 (a) W. Wang, S. P. Wang, X. B. Ma and J. L. Gong, Chem. Soc.
Rev., 2011, 40, 3703–3727; (b) C. A. Huff and M. S. Sanford, J.
Am. Chem. Soc., 2011, 133, 18122–18125; (c) S. Wesselbaum,
T. Vom Stein, J. Klankermayer and W. Leitner, Angew. Chem.,
Int. Ed., 2012, 51, 7499–7502; (d) J. Graciani,
K. Mudiyanselage, F. Xu, A. E. Baber, J. Evans,
S. D. Senanayake, D. J. Stacchiola, P. Liu, J. Hrbek,
J. F. Sanz and J. A. Rodriguez, Science, 2014, 345, 546–550;
(e) C. H. Lim, A. M. Holder, J. T. Hynes and
C. B. Musgrave, J. Am. Chem. Soc., 2014, 136, 16081–16095;
(f) S. Wesselbaum, V. Moha, M. Meuresch, S. Brosinski,
K. M. Thenert, J. Kothe, T. V. Stein, U. Englert,
M. Holscher, J. Klankermayer and W. Leitner, Chem. Sci.,
2015, 6, 693–704; (g) N. M. Rezayee, C. A. Huff and
M. S. Sanford, J. Am. Chem. Soc., 2015, 137, 1028–1031.
4 (a) G. Centi and S. Perathoner, Catal. Today, 2009, 148, 191–
205; (b) J. Goldemberg, Science, 2007, 315, 808–810.
5 T. Tatsumi, A. Muramatsu and H. Tominaga, Chem. Lett.,
1985, 593–594.
lysts, LiI or another promoter, tracer (methanol-13
C or
ethanol-13C2 if used), and 2 mL solvent were loaded into the
reactor. The reactor was sealed and purged three times with CO2
of 3 MPa, and then CO2 and hydrogen were charged to the
desired pressure at room temperature, respectively. The reactor
was placed in an air bath of constant temperature, and the
magnetic stirrer was started at 800 rpm. Aer reaction, the
reactor was cooled in an ice-water bath for 1 h, the residual gas
was released carefully in a hood. The liquid mixture was
analyzed by GC (Agilent 7890B) equipped with a ame ioniza-
tion detector and a HP-5 capillary column (0.32 mm in diameter
and 30 m in length) using toluene as the internal standard.
Identication of the liquid products was done using a GC-MS
(SHIMADZU-QP2010) as well as by comparing the retention
times of the standards in the GC traces (Fig. S4†). The yields of
the products were calculated from the GC data.
To test the reusability of the catalytic system, the alcohols
formed in the reaction were removed at 80 ꢀC under vacuum for
1.5 h, and the catalytic system (Ru3(CO)12–Rh2(CO)4Cl2–LiI/
DMI) was used directly for the next run.
6 (a) T. Inui and T. Yamamoto, Catal. Today, 1998, 45, 209–214;
(b) T. Inui, T. Yamamoto, M. Inoue, H. Hara, T. Takeguchi
and J. B. Kim, Appl. Catal., A, 1999, 186, 395–406.
7 H. Kurakata, Y. Izumi and K. Aika, Chem. Commun., 1996,
389–390.
Acknowledgements
The authors thank the National Natural Science Foundation of
China (21373234, 21173239, 21303224, 21321063) and the
Chinese Academy of Sciences (KJCX2.YW.H30). We are grateful
for the help of Dr Jinchao Wei in the GC-MS analysis.
8 L. S. Davy, D. Nieskens, Y. Ferrari, R. Liu and J. Kolonko,
Catal. Commun., 2011, 14, 111–113.
9 S. G. Li, H. J. Guo, C. R. Luo, H. R. Zhang, L. Xiong,
X. D. Chen and L. L. Ma, Chem. Lett., 2013, 143, 345–355.
10 R. Kieffer, M. Fujiwara, L. Udron and Y. Souma, Catal. Today,
1997, 36, 15–24.
11 M. Kishida, K. Yamada, H. Nagata and K. Wakabayashi,
Chem. Lett., 1994, 555–556.
12 H. Kusama, K. Okabe, K. Sayama and H. Arakawa, Catal.
Today, 1996, 28, 261–266.
13 K. K. Bando, K. Soga, K. Kunimori and H. Arakawa, Appl.
Catal., A, 1998, 175, 67–81.
Notes and references
1 (a) M. Aresta, Carbon Dioxide as Chemical Feedstock, Wiley–
VCH, Weinheim, 2010; (b) M. Y. He, Y. H. Sun and
B. X. Han, Angew. Chem., Int. Ed., 2013, 52, 9620–9633.
2 (a) T. Sakakura, J. C. Choi and H. Yasuda, Chem. Rev., 2007,
107, 2365–2387; (b) T. Yu, R. Cristiano and R. G. Weiss,
Chem. Soc. Rev., 2010, 39, 1435–1447; (c) M. Aresta,
A. Dibenedetto and A. Angelini, Chem. Rev., 2014, 114,
´
1709–1742; (d) P. G. Jessop, F. Joo and C. C. Tai, Coord.
Chem. Rev., 2004, 248, 2425–2442; (e) Y. H. Li, T. Yan,
K. Junge and M. Beller, Angew. Chem., Int. Ed., 2014, 53,
10476–10480; (f) K. Beydoun, G. Ghattas, K. Thenert,
J. Klankermayer and W. Leitner, Angew. Chem., Int. Ed.,
2014, 53, 11010–11014; (g) O. Jacquet, X. Frogneux,
C. D. N. Gomes and T. Cantat, Chem. Sci., 2013, 4, 2127–
2131; (h) X. J. Cui, X. C. Dai, Y. Zhang, Y. Q. Deng and
F. Shi, Chem. Sci., 2014, 5, 649–655; (i) C. Liu, J. H. Xie,
G. L. Tian, W. Li and Q. L. Zhou, Chem. Sci., 2015, 6, 2928–
14 H. Kusama, K. Okabe, K. Sayama and H. Arakawa, Energy,
1997, 22, 343–348.
15 K. Okabe, H. Yamada, T. Hanaoka, T. Matsuzaki, H. Arakawa
and Y. Abe, Chem. Lett., 2001, 904–905.
16 K. Tominaga, Y. SaSaki, M. Saito, K. Hagihara and
T. Watanabe, J. Mol. Catal., 1994, 89, 51–56.
17 P. M. Maitlis, J. Mol. Catal. A: Chem., 2003, 204–205, 55–62.
18 R. W. Wegman and K. G. Moloy, US Pat., 4 727 200, 1988.
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