Selective hydrogenation of 5-hydroxymethylfurfural to 2,5-bis-(hydroxymethyl)furan using Pt/MCM-41 in an aqueous medium: A simple approach

Article abstract of DOI:10.1039/c4gc01127a

The hydrogenation of HMF has been conducted in a neutral aqueous medium. Without any additive, HMF was hydrogenated to 2,5-bis-(hydroxymethyl)furan (BHMF) with complete conversion and selectivity (98.9%) using Pt/MCM-41 as catalyst. A very low temperature of 35 °C and 0.8 MPa of hydrogen pressure was used to accomplish the highest selectivity of BHMF within a reaction time of 2 h. Different reaction parameters such as reaction time, hydrogen pressure and the amount of water was optimized to achieve the highest catalytic activity. In particular, the presence or absence of water and the amount of water played an important role to determine the conversion and product distribution of the reaction. For instance, in the absence of water or a large excess of water, the selectivity of BHMF was decreased. In addition, instead of water the influence of three different groups of organic solvent were also explored to obtain BHMF under the studied reaction conditions. It has been observed that the studied organic solvents strongly influenced the catalytic performance, such as solvents with a negative δ value, which followed a clear trend with the substrate conversion, whereas no impact was observed for solvents with a positive δ value. Catalyst recycling experiments revealed that the catalyst could be recycled several times without any significant loss of catalytic activity.

Full text of DOI:10.1039/c4gc01127a

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Selective hydrogenation of 5-hydroxymethylfurfural
to 2,5-bis-(hydroxymethyl)furan using Pt/MCM-41
in an aqueous medium: a simple approach†
Cite this: DOI: 10.1039/c4gc01127a
a
a
a,b
Maya Chatterjee,* Takayuki Ishizaka and Hajime Kawanami*
The hydrogenation of HMF has been conducted in a neutral aqueous medium. Without any additive, HMF
was hydrogenated to 2,5-bis-(hydroxymethyl)furan (BHMF) with complete conversion and selectivity
(98.9%) using Pt/MCM-41 as catalyst. A very low temperature of 35 °C and 0.8 MPa of hydrogen pressure
was used to accomplish the highest selectivity of BHMF within a reaction time of 2 h. Different reaction
parameters such as reaction time, hydrogen pressure and the amount of water was optimized to achieve
the highest catalytic activity. In particular, the presence or absence of water and the amount of water
played an important role to determine the conversion and product distribution of the reaction. For
instance, in the absence of water or a large excess of water, the selectivity of BHMF was decreased. In
addition, instead of water the influence of three different groups of organic solvent were also explored
to obtain BHMF under the studied reaction conditions. It has been observed that the studied organic
solvents strongly influenced the catalytic performance, such as solvents with a negative δ value, which
followed a clear trend with the substrate conversion, whereas no impact was observed for solvents with a
positive δ value. Catalyst recycling experiments revealed that the catalyst could be recycled several times
without any significant loss of catalytic activity.
Received 17th June 2014,
Accepted 3rd August 2014
DOI: 10.1039/c4gc01127a
www.rsc.org/greenchem
also an important compound because of its application as a
Introduction
6
7
solvent, a monomer and also for the production of different
8
In recent years, considerable interest has grown for the devel- high-value chemicals such as 1,6-hexanediol. In this context,
opment of new pathways to obtain biomass derived platform several catalysts were tested by different methods using
9
10
11
chemicals. 5-Hydroxymethylfurfural (HMF) is considered to be sodium borohydride, formic acid
and formaldehyde.
a versatile platform molecule that can be produced by the acid- In catalytic hydrogenation, using molecular hydrogen, the
catalysed dehydrogenation of lignocellulose compounds such product distribution changed depending on the reaction con-
as glucose and fructose. A combination of furan ring, –OH and ditions and catalyst used. Schiavo et al. investigated the reac-
–CvO groups make it more appealing for various kind of tion in an aqueous medium in the presence of RANEY® Ni, Cu
transformations towards the sustainable formation of valuable chromite and carbon-supported metal catalysts at 140 °C and
1
,2
chemicals. In particular, the selective hydrogenation of the 7 MPa of hydrogen pressure. Cu or Pt catalysts yielded 80%–
CvO group in HMF to 2,5-bis-(hydroxymethyl)furan (BHMF), 100% of BHMF, while BHMTHF was the predominant product
–
1
2
has great potential for applications in the preparation of over Ni and Pd catalysts. Furthermore, HMF was converted to
resins, polymers and artificial fibers. It can be also used as an BHMF in a 96% yield over Au sub-nano clusters supported on
intermediate in the synthesis of drugs as well as crown alumina at 120 °C under 6.5 MPa of H
ethers. In addition, further hydrogenation of BHMF results obtained 81% selectivity of BHMF using a Ru/CeO
3
4
13
2
for 2 h. Alamillo et al.
catalyst
5
2
1
4
2
,5-bis-(hydroxymethyl)-tetrahydrofuran (BHMTHF), which is along with the formation of reduced BHMTHF. A bimetallic
catalyst such as Ni–Pd (Ni/Pd = 7 molar basis) was also used to
hydrogenate HMF and resulted in a 96% yield of BHMTHF at
1
5
a
Organic Synthesis Team, Research Center for Compact Chemical System,
40 °C and 8 MPa of hydrogen pressure. In a recent report,
Tamura et al. applied a Ir–ReO catalyst for the hydrogenation
AIST Tohoku, 4-2-1, Nigatake, Miyagino-ku, Sendai 983-8551, Japan.
Tel: +81 22 237 5213
x
of HMF and obtained a 99% yield of BHMF after 6 h of
b
CREST, Japan Science and Technology (JST), 4-1-8, Honcho, Kawaguchi,
16
reaction at 30 °C and a hydrogen pressure of 0.8 MPa. While
Saitama 332-0012, Japan. E-mail: c-maya@aist.go.jp, h-kawanami@aist.go.jp;
Fax: +81 22 237 5388
preparing this manuscript another group detected a 99% yield
of BHMF at 100 °C after 3 h of reaction in ethanol over a
†
Electronic supplementary information (ESI) available. See DOI: 10.1039/c4gc01127a
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copper-doped porous metal oxide prepared by the calcination Table 1 Catalyst screening
1
7
of hydrotalcite. Thus, in most of the cases, higher hydrogen
pressure, longer reaction time, organic solvents or additional
metal oxide additive were used to achieve a high yield of Entry Catalyst
BHMF.
Product selectivity (%)
Conv. (%) BHMF MF MFA ROP UK
1
2
3
4
5
6
7
8
9
1
1
Ni/MCM-41
13.0
37.0
100.0
16.2
>1
42.1
9.0
89.0
10.2
98.9
73.6
—
60.7
43.1
0.0
2.4
20.0 12.1
1.1 0.0
0.0 11.1
0.0
5.5 3.1
48.2 9.5
0.0 0.0
13.8 1.5
In the present work, we have attempted the hydrogenation
of HMF under a mild reaction conditions (temperature =
Pd/MCM-41
Pt/MCM-41
Au/MCM-41
Ru/MCM-41
Rh/MCM-41
Ir/MCM-41
Pt/MCM-41
Pt/MCM/41
Pt/MCM/41
Pt/MCM-41
3
5 °C, PH2 = 0.8 MPa, reaction time = 2 h) in an aqueous
—
—
—
—
medium using Pt/MCM-41 as catalyst without any additive to
improve the catalytic performance.
0
27.0
3.0
0.0
32.4 3.9
29.9 0.0
0.0 0.0
a
b
75.4
2.6
0.0 73.0
—
—
85.6
90.1
0.0
—
—
c
0
1
15.2
96.6
—
99.2
—
0.8
d
0.0 0.0
Results and discussion
Reaction conditions: catalyst: substrate (wt ratio) = 1 : 5; temperature =
5 °C; reaction time = 2 h; water = 2 ml; PH2 = 0.8 MPa; BHMF = 2,5-
A typical reaction profile for HMF hydrogenation under the
working conditions is shown in Scheme 1. Accordingly, HMF bis-(hydroxymethyl)furan, MF = 5-methylfurfural; MFA = 5-methylfurfuryl
was hydrogenated to BHMF followed by the conversion to MFA
and MTHFA. In a minor route, MF was formed from HMF via
3
alcohol, UK = unknown (unidentified), ROP = ring opening products
including 1,2-hexanediol, 2,5-hexanedione and 4-hydroxypentanoic
a
b
c
acid. MF as substrate. BHMF as substrate. BHMF as substrate and
d
th
hydrogenolysis.
the reaction time is 6 h. 7 recycle.
Catalyst screening
Rh > Ir. BHMF, which derives from the selective hydrogenation
We have targeted the development of a simple method for of the –CvO bond was more prominent over Ni, Pt, Au and Rh
hydrogenation of HMF to BHMF using a heterogeneous cata- but a relatively high selectivity of MF, the hydrogenolysis
lyst. In search of the desired catalyst, the reaction was con- product of HMF (27%) was detected in the presence of Ir. In
ducted over different metals such as Ni, Pt, Pd, Au, Ru, Rh and contrast, the Pd catalyst was very active, which produced a 48%
Ir supported on MCM-41. To avoid the complexity generated yield of ring opening products (ROP), including 2,5-hexane-
from the support material, neutral Si-MCM-41 was used as the dione (hydrogenolysis and hydrolysis) and 4-hydroxypentanoic
support. All the catalysts contain ∼1 wt% of metal. Table 1 acid (hydration and reduction) (Table 1; entry 2), highest
shows the result of catalyst screening on the hydrogenation of among the other catalysts used. In addition, some unidentified
HMF. Depending on the metal, the catalytic performance was products (UK) were also detected using the Ni, Pd and Rh cata-
different. Regarding the conversion of HMF, Pt gave complete lysts. Hence, the product distribution was strongly influenced
conversion (entry 3), whereas 35% to 40% conversion was by the nature of the metal used. Therefore, depending on the
detected over Pd and Rh catalysts (entries 2 and 6). In other target performance to achieve the highest conversion of HMF
cases, the conversion was as low as 13.0% and 16.2% for Ni and selectivity to BHMF, Pt/MCM-41 was selected as an
and Au (entries 1 and 4), respectively, and less than 10% for effective catalyst for the hydrogenation of HMF. We also opti-
the Ir catalyst (entry 7). Among the utilized catalysts, Ru (entry mized different reaction parameters to obtain high catalytic
5
) was completely inactive under the reaction conditions activity. In the absence of catalyst no reaction was observed.
studied. The metal supported catalysts followed the conversion
order of Pt > Rh > Pd ≈ Ni ≈ Au > Ir. Considering the product
Effect of reaction time
distribution, except Pd, BHMF was the major product detected To understand the temporal evaluation of products, during the
for all the catalysts and the selectivity order was Pt > Ni > Au > hydrogenation of HMF using the Pt/MCM-41 catalyst, the
Scheme 1 Reaction path of HMF hydrogenation under the reaction conditions studied.
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Effect of hydrogen pressure
The impact of hydrogen pressure on the conversion of HMF
under the studied reaction conditions is shown in Fig. 2.
Hydrogen pressure was varied from 0.2 to 4 MPa, while
keeping the other parameters constant. As expected, the con-
version of HMF was increased from 67.6% to 100% along with
an increase in pressure from 0.2 to 0.8 MPa, and then remains
constant. The selectivity of BHMF slightly dropped to 86.7%
when the high pressure of 4 MPa was used. Interestingly, at
higher pressure, the selectivity of MFA was enhanced from 1%
to 11%. As mentioned beforehand, MFA was generated by the
hydrogenation of MF; hence, it may confirm that the reaction
Fig. 1 Evaluation of product yield as a function of reaction time. Reac- became faster at higher hydrogen pressure. In addition, ROP
H
tion conditions: P 2
= 0.8 MPa; catalyst: substrate (wt ratio) = 1 : 5;
were also detected at a very low selectivity of 2.1%. Therefore,
to achieve a higher conversion and selectivity of BHMF, a lower
hydrogen pressure of 0.8 MPa was chosen throughout the
investigations towards optimization of the other parameters.
No conversion of HMF was detected in the absence of
hydrogen.
Temp. = 35 °C and water = 2 ml.
reaction was studied as a function of reaction time and the
results are shown in Fig. 1. As the time changed from 15 min
to 18 h, the product distribution changed in a complex
manner. The major product observed after 15 min, was Variation of the amount of water
BHMF (∼30%), along with the formation of minor products
In this study, an aqueous solution of HMF was used for hydro-
such as MF (∼5%) and MFA (∼2%). As time progressed, the
yield of MF decreased rapidly to zero. However, the yield of
BHMF increased monotonically, and reached its maximum
genation over Pt/MCM-41. To predict the role of water as a
solvent, experiments were conducted in the presence and in
the absence of water (Fig. 3). According to the results, in the
absence of water, conversion as well as the selectivity of BHMF
were low at ∼40% and 15.3%, respectively. On the other hand,
when water was used as a solvent, the conversion and the
selectivity of BHMF was enhanced significantly. Hence, the
presence of water was required to achieve high conversion and
selectivity of BHMF. For example, the addition of 1 ml of water
increased the conversion to 86% and the selectivity of BHMF
was improved (95.8%). A similar result was also observed
during the hydrogenation of bisphenol-A in water using Ru/
(
98.9%) after 2 h of reaction. By increasing the reaction time
from 2 h to 6 h the yield of MFA changed from 1.1% to 9.9%,
followed by the formation of MTHFA. Additional experimen-
tation with the prolonged reaction time of 18 h resulted in
the decreased yield of BHMF to 69.5%, whereas the yield of
MFA and MTHFA were increased to 11.4% and 16%, respect-
ively. To confirm the validity of the reaction pathway as
depicted in Scheme 1, experiments were conducted separately
with MF and BHMF as starting materials under similar reac-
tion conditions and the results are shown in Table 1 (entries
19
MCM-41 as catalyst. They suggested that the hydroxyl groups
8
and 9). The results revealed that MF is more reactive and
on the silica surface could form hydrogen bonding with water
molecules. The hydrogen bonds could help the water mole-
cules surround the catalyst surface, thus, creating a better dis-
persion of the catalyst, which in turn provide better catalytic
within a reaction time of 2 h, the intermediate was converted
mainly to MFA with a conversion of 75.4%. On the contrary,
under similar reaction conditions, the conversion of BHMF
was very low at ∼2% and the main product detected was MFA
20
activity in an aqueous medium. Recently, it has been also
(
Table 1, entry 9), and the conversion was increased to only
∼
13% even after 6 h of reaction (Table 1; entry 10). Hence, a
fast transformation of MF to MFA could be the reason behind
the initial formation of MFA, which was also reported pre-
1
8
viously and a slow reaction of BHMF to MFA could be pre-
dicted under the working conditions. To restate, HMF was
hydrogenated to BHMF (major route) and the yield of BHMF
increased with time, whereas MF, which was obtained via
hydrogenolysis (minor route) was diminished to zero, and the
yield of MFA remained almost constant within the reaction
time of 2 h. This observation tempted us to suggest the con-
version of MF or MFA to BHMF. However, at this stage, we
have no direct experimental evidence for the specific reaction
pathway to confirm this point; thus, it is shown as a possible
reaction pathway (dotted line) in Scheme 1 but it needs
further investigation.
Fig. 2 Effect of hydrogen pressure on the hydrogenation of HMF. Reac-
tion conditions: catalyst : substrate (wt ratio) = 1 : 5; Temp. = 35 °C,
water = 2 ml and reaction time = 2 h.
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Fig. 4 Effect of pH on the hydrogenation of HMF in water. Reaction
conditions: catalyst: substrate (wt ratio) = 1 : 5; PH2 = 0.8 MPa, Temp. =
Fig. 3 Variation of the amount of water. Reaction conditions: catalyst:
substrate (wt ratio) = 1 : 5; PH2 = 0.8 MPa, Temp. = 35 °C, and reaction
time = 2 h.
35 °C, water = 2 ml and reaction time = 2 h.
tetrahydrofuran (THF)) and (iii) nonpolar (hexane) solvents
were used to elucidate the solvent effect on the hydrogenation
of HMF.
pointed out that water could accelerate chemical reactions, in
which hydrogen was used as a reactant.
However, the role of water is complicated and needs separate
attention. After confirming the necessity of water, the volume of
water was varied from 1 to 16 ml to investigate its effect on the
catalytic activity (Fig. 3). The conversion of HMF increased from
2
1
Table 2 summarizes the results of the hydrogenation of
HMF conducted in several solvents at 35 °C under 0.8 MPa of
hydrogen for 2 h. From the results it is evident that the cataly-
tic activity was strongly dependent on the solvent used. Among
the solvents from first group, the conversion decreases in the
following order: methanol (72.1%) > ethanol (55.6%) > propa-
nol (27.2%) > butanol (24.4%). There are several parameters
related to solvent properties accounting for the solvent effect
on the catalytic reactions. However, a simple approach is the
consideration of donor and acceptor numbers of solvents,
which are related to a quantitative measure of Lewis basicity
and acidity, respectively. Here we plotted the conversion of
HMF with the δ value of the solvents (Fig. 5). This δ value rep-
resents the difference between donor number and acceptor
8
2
6.5% to 100% upon increasing the amount of water from 1 to
ml and then decreased to 71.4% with further addition of water
(16 ml). The decreased conversion upon addition of an excess of
water was attributed to the dilution effect, which causes reduced
collisions between the reactants and catalyst. Interestingly, the
selectivity of BHMF was not significantly affected with an
additional amount of water. Hence, an optimum amount of
water (2 ml) was used throughout the experiments under the
stated reaction conditions. From the results, it could be
suggested that the addition of an appropriate amount of water
has a strong influence to accelerate the reaction.
2
2
number. From the results, it is evident that the behaviour of
the studied solvents can be divided into two groups: (i) sol-
vents with negative δ values are capable of accepting electrons
and (ii) solvents with positive δ values with the capability of
donating electrons. The first group of solvents are methanol,
ethanol, butanol and propanol, providing a higher conversion
of HMF. A clear trend was observed with the δ value and the
Effect of pH
According to the literature, acidic by-products or solvent phase
acidity affect the product selectivity during the hydrogenation
1
2
of HMF. Thus, the reaction was performed in acidic and
basic conditions and the results shown in Fig. 4, which
suggest poor catalytic performance was observed under both
acidic or basic conditions. When the hydrogenation of HMF
was conducted in an acidic medium of pH ∼ 3, this reaction
proceeded with 73% conversion, and the selectivity of BHMF
dropped significantly due to the formation of unidentified by-
products. On the other hand, in a basic aqueous solution, the
transformation of HMF was slower, which resulted in a lower
conversion and selectivity of 40% and ∼80%, respectively.
Hence, the results suggest that under the studied reaction con-
ditions, a neutral aqueous medium was the best choice for the
hydrogenation of HMF to BHMF.
Table 2 Hydrogenation of HMF in different organic solvents
Product yield (%)
Entry Solvent
Conv. (%) BHMF MF MFA HD
UK
0.0
3.4
9.1
1
2
3
4
5
6
7
8
Water
100.0
72.1
55.6
27.2
24.4
12.0
18.2
10.1
98.9
89.8
87.2
77.9
70.5
41.3
32.4
82.5
0.0 1.1
5.6 1.2
3.7 0.0
3.6 1.2
1.8 0.0
0.0 0.0
5.8 0.0
6.6 1.0
0.0
0.0
0.0
0.0
Methanol
Ethanol
Propanol
Butanol
Acetone
THF
17.3
6.2/0 21.5
0.0
54.8/0
0.0
58.3
7.0
9.9
Comparison with other solvents
Hexane
Instead of water, the hydrogenation of HMF was conducted in
different types of organic solvents. Three different categories
of solvent including (i) polar protic, (methanol, ethanol,
Reaction conditions: catalyst: substrate (wt ratio) = 1 : 5; temperature =
5 °C; reaction time = 2 h; Solvent = 2 ml; PH2 = 0.8 MPa; BHMF = 2,5-
bis-(hydroxymethyl)furan, MF = 5-methylfurfural; MFA = 5-methylfurfuryl
3
butanol and propanol), (ii) polar aprotic (acetone and alcohol, HD = 1,2-hexanediol, UK = unknown (unidentified products).
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is possible to recycle the catalyst at least six times. The result
th
after the 6 recycle suggested a moderate decrease in the
activity (Table 1, entry 11; ESI Fig. S3†) possibly due to slight
changes in the structure of the catalyst and Pt particle size
(
ESI Fig. S1(b) and S2(b)†).
Conclusion
In conclusion, a simple method has been demonstrated
towards the hydrogenation of HMF to BHMF in an aqueous
medium under mild reaction conditions. The described
method was highly selective for BHMF. The selectivity of the
targeted compound was affected by hydrogen pressure, as well
Fig. 5 The relationship between conversion of HMF and the δ value
of the solvent. Reaction conditions: catalyst: substrate (wt ratio) = 1 : 5;
H
P 2 = 0.8 MPa, Temp. = 35 °C, solvent = 2 ml and reaction time = 2 h.
substrate conversion. In the presence of those solvents the con- as the presence or absence of water. In particular, an appropri-
version decreased with an increase in the δ value, which was ate amount of water was necessary to obtain a high yield of the
attributed to a possible correlation between the Lewis acidity targeted compound but an excess of water hampered the cata-
and substrate conversion. In addition, the selectivity of BHMF lytic activity. In addition, a neutral medium was preferred over
was almost the same for methanol (89.8%; Table 2, entry 2) basic or acidic medium. A comparison with different organic
and ethanol (87.2%; Table 2, entry 3), whereas a comparatively solvents revealed the superiority of water as a reaction medium
lower selectivity of ∼78% and 77% were detected in propanol for this reaction. Further work is necessary to understand the
and butanol, respectively (Table 2, entries 4 and 5). The sol- role of the medium. It is believed that this strategy could be
vents with positive δ values have no effect on the conversion. extended to the other furan compounds and tuning the reac-
In the presence of the second group of solvents (acetone, tion conditions might provide scope to obtain other valuable
hexane and THF), the conversion of HMF was very poor and in compounds.
the range of ∼15%, which provoked us to suggest that partial
blocking of the metal active sites was occurring due to solvent
adsorption. The role of solvent in a reaction is a complex Experimental section
matter when catalysts containing noble metals are used
Reagents: 5-hydroxymethylfurfural, cetyltrimethylammonium
bromide and H PtCl were obtained from Aldrich. Tetraethyl
2 6
because of their tendency to interact with solvents containing
2
3
oxygen, nitrogen and sulphur. From the above results, we
suggest that water was the best choice as solvent for the hydro-
genation of HMF to BHMF under the reaction conditions
studied, but solvents with negative δ values provide better per-
formance in comparison to solvents with positive δ values.
orthosilicate and organic solvents (methanol, ethanol, butanol,
-propanol, acetone, hexane, THF and chloroform) were pur-
1
chased from Wako Pure chemicals.
Catalyst synthesis
Reaction pathway
Hydrothermal synthesis of Pt/MCM-41 was based on the
2
8
It is too early to predict the reaction path of HMF hydrogen- method described in our previous work. In brief, sodium
ation over Pt/MCM-41 in water. However, from the accumu- hydroxide and cetyltrimethylammonium bromide (CTAB) were
lated experimental results, it was observed that BHMF was added to de-ionized water and stirred until complete dissolu-
obtained as the major product. In the present reaction con- tion. A ∼1 wt% solution of Pt salt (H PtCl ) was introduced to
2
6
ditions, Pt/MCM-41 was selectively hydrogenating the –CvO the resulting gel and again stirred for 2 h, followed by the
group of HMF and consequently BHMF was formed. A similar addition of tetraethyl orthosilicate (TEOS) with stirring conti-
trend of Pt catalysis was also observed during the hydrogen- nued for another 2 h to reach homogeneity. The final gel com-
2
4
ation of cinnamaldehyde over a Pt catalyst. Hence, primarily, position was as follows: 1TEOS : 0.45Na O : 0.12CTAB : 118H O.
2
2
it could be speculated that the adsorption of HMF takes place The gel was then autoclaved at 140 °C for 48 h. The solid
via the –CvO group and the reaction occurred through the for- product was then filtered, washed thoroughly with de-ionized
2
5
mation of an alkoxide intermediate. Alkoxide formation is water followed by oven drying at 60 °C. To remove the tem-
favoured at low temperatures, followed by the subsequent plate, the as-synthesized material was calcined at 550 °C for
addition of a second hydrogen atom to produce BHMF. A 8 h in air. Before application, the calcined material was pri-
similar mechanism was also predicted for the hydrogenation marily characterized by XRD and TEM to obtain an insight of
2
6,27
of furfural to furfuryl alcohol.
its structure (ESI Fig. S1(a) and S2(a)†).
Catalyst recycling
Catalytic activity
After reaction, the catalyst was separated by simple filtration The hydrogenation of HMF was conducted in a 50 ml batch
and was ready to recycle. Recycling experiments showed that it reactor. In a typical experiment, a specified amount of catalyst
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(
0.1 g) was placed into the reactor containing a 2 ml aqueous
8 (a) T. J. Connolly, J. L. Considine, Z. Ding, B. Forsatz,
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oven equipped with a fan heater to maintain a constant temp-
erature. After reaching the desired temperature, hydrogen at
the required pressure was introduced into the reactor. The
reaction mixture was stirred continuously with a Teflon-coated
magnetic bar during the reaction. After the reaction, the liquid
part was separated by simple filtration. Finally, the product
9 L. Cottier, G. R. Descotes and Y. Soro, Synth. Commun.,
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GC-MS (Varian Saturn 2200). Quantification of the products Int. Ed., 2010, 49, 6616.
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product. The selectivity to each product was calculated by the Anal. Chem., 1954, 26, 898.
following expression S = C /∑C , where C is the concentration 12 V. Schiavo, G. Descotes and J. Mentech, Bull. Soc. Chim. Fr.,
i
i
p
i
of the product ‘i’ and ∑Cp is the total concentration of the
1991, 128, 704.
product.
13 J. Ohyama, A. Esaki, Y. Yamamoto, S. Arai and A. Satsuma,
RSC Adv., 2013, 3, 1033.
1
4 R. Alamillo, M. Tucker, M. Chia, Y. Pagán-Torres and
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Acknowledgements
1
H. Kawanami was funded by the Japan-U.S. cooperation
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