Chemoselective hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol

Article abstract of DOI:10.1039/b822942b

Direct conversion of tetrahydrofurfuryl alcohol, which is one of the biomass-derived chemicals, to 1,5-pentanediol was realized by chemoselective hydrogenolysis catalyzed by Rh/SiO₂ modified with ReO_x species, and this reaction route gave higher yield than the conventional multi-step method.

Full text of DOI:10.1039/b822942b

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Chemoselective hydrogenolysis of tetrahydrofurfuryl alcohol
to 1,5-pentanediolw
Shuichi Koso,a Ippei Furikado,a Akira Shimao,a Tomohisa Miyazawa,a Kimio Kunimoria
and Keiichi Tomishige*ab
Received (in Cambridge, UK) 19th December 2008, Accepted 27th January 2009
First published as an Advance Article on the web 26th February 2009
DOI: 10.1039/b822942b
Direct conversion of tetrahydrofurfuryl alcohol, which is one of
the biomass-derived chemicals, to 1,5-pentanediol was realized
by chemoselective hydrogenolysis catalyzed by Rh/SiO2
modified with ReOx species, and this reaction route gave higher
yield than the conventional multi-step method.
The Rh–ReOx/SiO2 catalysts were prepared by impregnation
method using RhCl3Á3H2O and NH4ReO4. The loading
amount of Rh was 4 wt%, and that of Re was in the range
of 0.25–1.0 by molar ratio of Re to Rh. Commercially
available 5 wt% Ru/C, copper chromite, and RANEYs Ni
were used as reference catalysts. Catalytic testing of tetra-
hydrofurfuryl alcohol, tetrahydrofuran, and tetrahydropyran-
2-methanol was performed in a stainless steel autoclave
with an inserted glass vessel. Products were analyzed by a
gas chromatograph. Catalysts were characterized by CO
adsorption measurement, transmission electron microscope
observation, powder X-ray diffraction, and X-ray absorption
spectroscopy. Methods for catalyst preparation, activity test,
product analysis, and catalyst characterization are described in
detail in the ESI.w
Utilization of biomass as a renewable raw material will
gain importance in the industrial production of chemical
substances for sustainability and as a substitute for petroleum
for energy production.1,2 Since biomass-related raw materials
usually have a high oxygen content, useful oxygenates such as
terminal-diols3 will be one of the target chemicals derived from
biomasses. Terminal-diols, which have a linear carbon–carbon
chain and carbons at both edges with the OH group, have been
used as monomers for the production of polyesters and
polyurethanes. Development of catalysts and catalytic reaction
for the production of terminal-diols from renewable resources
has been needed,3 and one candidate among the terminal-diols
is 1,5-pentanediol. It has been known that 1,5-pentanediol is
formed by hydrogenolysis of tetrahydrofurfuryl alcohol.
Tetrahydrofurfuryl alcohol is one of the derivatives of furfural,
which has been produced by acidic degradation of hemicellulose
contained in agricultural raw materials abundantly.4 However,
the selectivity to 1,5-pentanediol was low, and 1,2-pentanediol
tends to be formed more preferably than 1,5-pentanediol over
conventional hydrogenolysis catalysts.5 This low selectivity to
1,5-pentanediol is regarded as the limit of heterogeneous
catalyst systems for hydrogenolysis.3 Therefore, it has been
proposed that 1,5-pentanediol is produced via dihydropyran
and d-hydroxyvaleraldehyde from tetrahydrofurfuryl alcohol
achieving 70% yield.6 This method circumvents the
hydrogenolysis with low selectivity, but three steps with
isolation and purification of the intermediates by distillation
are needed.6 This communication reports a heterogeneous
catalyst for the production of 1,5-pentanediol by chemoselective
hydrogenolysis of tetrahydrofurfuryl alcohol. We found that
Rh–ReOx/SiO2 is much more active and selective in the
hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol
than conventional hydrogenolysis catalysts.
In the hydrogenolysis of tetrahydrofurfuryl alcohol,
Rh–ReOx/SiO2 (Re/Rh
=
0.5) gave 77% yield of
1,5-pentanediol after 24 h (Table 1, entry 1), and higher yield
than the reported multi-step method6 was obtained. In order
to compare the catalytic activity, 4 h reaction time was
applied. The activity of Rh/SiO2 and ReOx/SiO2 is much
lower than Rh–ReOx/SiO2 (Table 1, entries 5, 6), although
Rh/SiO2 is effective in the hydrogenolysis of glycerol as
reported previously7. The catalyst stability in the hydrogenolysis
of tetrahydrofurfuryl alcohol was verified over Rh–ReOx/SiO2
(Re/Rh = 0.5) by the recycle use of the catalyst. The product
distribution on the reused catalyst was almost the same as that
on the fresh catalyst, and the conversion decreased a little to
52.0% from 56.9%, which is due to a small amount of Re
leaching from the ICP analysis as described in the ESI.w In
addition, Ru/C,8–10 copper chromite,10,11 and RANEYs
Ni10,12 have been used for hydrogenolysis of glycerol to
propylene glycol. Therefore, these catalysts were also
evaluated and the results are listed in Table 1. The Ru/C
showed much lower activity than the Rh–ReOx/SiO2
(Re/Rh = 0.5), and the degradation by the cracking of the
C–C bond was mainly catalyzed by the Ru/C (Table 1, entry
7). This behavior has also been observed in the reaction of
glycerol. Since the activity of copper chromite and RANEYs
Ni catalysts were extremely low at 393 K and 0.05 g catalyst,
the amount of the catalysts and the reaction temperature were
increased. In spite of higher reaction temperature and larger
catalyst amount, copper chromite and RANEYs Ni exhibited
a very low catalytic activity (Table 1, entries 8, 9). It is
concluded that these conventional hydrogenolysis catalysts
are not suitable for the chemoselective hydrogenolysis of
tetrahydrofurfuryl alcohol to 1,5-pentanediol.
a Institute of Materials Science, University of Tsukuba, 1-1-1,
Tennodai, Tsukuba, Ibaraki, 305-8573, Japan.
E-mail: tomi@tulip.sannet.ne.jp; Fax: 81-029-853-5499
b International Center for Materials Nanoarchitectonics Satellite
(MANA), National Institute of Materials Science (NIMS) and
University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki, 305-8573,
Japan
w Electronic supplementary information (ESI) available: Additional
experimental details. See DOI: 10.1039/b822942b
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Results of the hydrogenolysis of tetrahydrofurfuryl alcohol, tetrahydrofuran and tetrahydropyran-2-methanol
Molar ratio Catalyst
Re/Rh
Reaction Conversion
temperature/K Time/h (%)
Entries Catalyst
weight/g
Selectivity of product (%)
Tetrahydrofurfuryl alcoholc
1.5-PeD
80.1
94.2
85.1
84.6
18.0
0.0
15.1
0.0
13.1
1,2-PeD
0.0
0.0
0.0
0.0
61.7
31.2
26.1
9.4
1-PeOH
15.9
4.4
11.2
12.0
6.2
5.1
7.8
Others
4.0
1.4
3.7
3.4
14.1
63.7
51.0
87.6
65.2
1
2
3
4
5
6
7
8
9
Rh–ReOx/SiO2
Rh–ReOx/SiO2
Rh–ReOx/SiO2
Rh–ReOx/SiO2
Rh/SiO2
ReOx/SiO2
Ru/C
Copper chromite
RANEYs Ni
0.5
0.5
0.25
1.0
—
—
—
—
—
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.50
0.50
393
393
393
393
393
393
393
453
453
24
4
4
4
4
4
4
4
4
96.2
56.9
40.8
48.3
5.7
b
o0.1
5.0
0.6
3.0
8.9
0.2
12.7
Tetrahydrofurand
1-BuOH
499.9
499.9
10
11
Rh–ReOx/SiO2
Rh/SiO2
0.5
—
0.05
0.05
393
393
4
4
1.5
9.4
Tetrahydropyran-2-methanole
1,6-HeD 1,2-HeD 1-HeOH Others
12
13
Rh–ReOx/SiO2
Rh/SiO2
0.5
—
0.05
0.05
393
393
4
4
32.2
2.7
89.7
13.2
0.0
34.5
7.1
25.4
3.2
26.9
a
b
c
Reaction conditions: 8.0 MPa initial H2 pressure. Loading amount on ReOx/SiO2 the same as that of Rh–ReOx/SiO2 (Re/Rh = 0.5). 20 ml
d
e
5 wt% aqueous solution of tetrahydrofurfuryl alcohol. 20 ml 5 wt% aqueous solution of tetrahydrofuran. 10 ml 5 wt% aqueous solution of
tetrahydropyran-2-methanol. PeD = pentanediol. PeOH = pentanol. BuOH = butanol. HeD = hexanediol. HeOH = hexanol.
Since ReOx/SiO2 showed no hydrogenolysis activity, Rh is
an essential component for the hydrogenolysis reaction and
synergy between Rh and Re enhanced the activity and
chemoselectivity simultaneously. In order to elucidate the
mechanism of the synergy, characterization of the active
structure is important. At first, the number of surface Rh
atoms can be determined by the measurement of the amount
of CO adsorbed because CO is adsorbed more preferably on
the surface of Rh atoms than of ReOx species at room
temperature.13,14 The amount of CO adsorbed (the molar
ratio of adsorbed CO to Rh: CO/Rh) on Rh–ReOx/SiO2
(Re/Rh = 0.5) (CO/Rh = 0.17) was much smaller than that
of Rh/SiO2 (CO/Rh = 0.39). The average particle size of
Rh–ReOx/SiO2 (Re/Rh = 0.5) and Rh/SiO2 was determined
to be 4.3 Æ 0.4 and 3.5 Æ 0.4 nm by TEM observation,
respectively (ESIw). In addition, the crystal size of Rh
metal determined by X-ray diffraction was 3.2 Æ 0.3 nm and
2.8 Æ 0.3 nm on Rh–ReOx/SiO2 and Rh/SiO2, and the
tendency was similar to that from TEM observation.
Considering that the particle size of Rh–ReOx/SiO2 was
similar to that of Rh/SiO2, it is suggested that the CO
adsorption on Rh–ReOx/SiO2 can be suppressed, probably
because of the covering of Rh metal particles with Re species.
Next, in order to characterize the interaction of Re species
with Rh metal particles, EXAFS analysis was carried out.
Table 2 lists the curve fitting results of Re L3-edge EXAFS of
Rh–ReOx/SiO2 (Re/Rh = 0.5) after the reaction. The
detection of the Re–O bond indicates that Re species is not
fully reduced to metallic state and this is also supported by Re
L3–edge X-ray near edge structure (Fig. S3, ESIw). The Re–Rh
bond is related to the suppression of CO adsorption and the
Re atoms interact directly with Rh species judging from the
bond length of 0.268 nm. This means there are no oxygen
atoms located between Rh and Re species and there is no
interaction between Rh and oxygen. In addition, oxygen
atoms in the Re–O bond are originated mainly from the
precursor of Re species. If most oxygen atoms are originated
from the support, the Re should be located between the Rh
metal particles and the support. In this case, a bare Rh metal
surface is exposed and this cannot explain the complete
switching of product selectivity by Re addition as mentioned
below. The Re L3-edge EXAFS analysis suggests the formation
of small ReOx clusters attached on the surface of Rh metal
particles on Rh–ReOx/SiO2 from the presence of the Re–Re
bond. The structure of Rh–ReOx is compared to a core-shell
one where the core and shell consist of ReOx clusters and Rh
metal particles, respectively. This structure was constructed
after the reduction as indicated by similar XANES and
EXAFS results (Fig. S3, ESIw) to that after the reaction, and
it was maintained during the reaction. The amount of CO
adsorbed on the used catalyst (CO/Rh = 0.15) was almost the
same as that on the fresh catalyst, and this also supports
the maintenance of the active structure. On the other hand, the
catalytic activity of tetrahydrofurfuryl alcohol hydrogenolysis
was much dependent on the additive amount of ReOx on
Rh–ReOx/SiO2 (Table 1, entries 2–4), and the maximum
was observed at Re/Rh = 0.5. Too much Re addition can
decrease the Rh surface atoms and catalytic activity. Another
interesting point is that a main product over Rh–ReOx/SiO2
was 1,5-pentanediol (Table 1, entries 1–4), on the other hand,
that over Rh/SiO2 was 1,2-pentanediol (Table 1, entry 5). In
particular, the formation of 1,2-pentanediol and 2-pentanol in
the hydrogenolysis of tetrahydrofurfuryl alcohol was not
detected at all over Rh–ReOx/SiO2 (Table 1, entries 1–4). This
indicates that the C–O bond in Scheme 1(a) among three types
of the C–O bond in the molecule of tetrahydrofurfuryl alcohol
is dissociated selectively over Rh–ReOx/SiO2. In contrast, a
different C–O bond is dissociated over Rh/SiO2 (Scheme 1(b)).
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Table 2 The curve fitting results of Re L3-edge EXAFS of Rh–ReOx/SiO2 after the hydrogenolysis of tetrahydrofurfuryl alcohol
Catalyst
Molar ratio Re/Rh
0.5
Shells
CNa
R/10À1 nmb
s/10À1 nmc
DE0/eVd
Rf (%)e
Rh–ReOx/SiO2
Re–O
Re–Rh
Re–Re
1.3
3.6
2.8
2.13
2.68
2.73
0.099
0.063
0.064
10.8
10.9
2.6
1.0
a
b
Coordination number. Bond distance. Debye–Waller factor. Difference in the origin of photoelectron energy between the reference and the
c
d
e
sample. Residual factor. Fourier filtering range: 0.129–0.301 nm.
production from transesterification of vegetable oils. As a
result, the tetrahydropyran-2-methanol can be regarded as a
biomass-derived chemical. The Rh–ReOx/SiO2 showed
much higher activity than Rh/SiO2 and the Re modification
switched the selectivity from 1,2-hexanediol to 1,6-hexanediol.
It is found that Rh–ReOx/SiO2 is applicable to the chemo-
selective hydrogenolysis of tetrahydropyran-2-methanol to
1,6-hexanediol (Scheme S1, ESIw). It is concluded that
chemoselective hydrogenolysis to terminal-diols such as
Scheme 1 Reaction routes in the hydrogenolysis of tetrahydrofurfuryl
1,5-pentanediol and 1,6-hexanediol is catalyzed effectively by
heterogeneous Rh–ReOx/SiO2 catalysts, and this work
alcohol.
demonstrated that high chemoselectivity is available on
This indicates that the modification of Rh/SiO2 with
heterogeneous catalysts with suitable active structures in the
ReOx switched the main product from 1,2-pentanediol to
catalytic conversion of biomass-derived chemicals containing
1,5-pentanediol by changing the dissociation of the C–O bond.
various functional groups.
This work was in part supported by World Premier
High selectivity of Rh–ReOx/SiO2 can be realized by the
promotion of the 1,5-pentanediol route (Scheme 1(a)) and
International Research Center (WPI) Initiative on Materials
simultaneous suppression of the route to 1,2-pentanediol. In
Nanoarchitectonics, MEXT, Japan. X-Ray absorption spectra
order to evaluate the suppression, the hydrogenolysis of
were measured at BL-01B1 in the SPring-8 with the
tetrahydrofuran was also tested as listed in Table 1. The
approval of the Japan Synchrotron Radiation research center
(JASRI, proposal No 2008B1235).
Rh/SiO2 showed
a higher activity than Rh–ReOx/SiO2
(Table 1, entries 10, 11), and the activity order in the
tetrahydrofuran hydrogenolysis was opposite to that in the
tetrahydrofurfuryl alcohol hydrogenolysis. This tendency
represents that the addition of ReOx accelerates the tetra-
hydrofurfuryl alcohol hydrogenolysis and decelerates the
tetrahydrofuran hydrogenolysis. This can bring out high
chemoselectivity in the hydrogenolysis of tetrahydrofurfuryl
alcohol. In the case of the hydrogenolysis of tetrahydrofuran,
the reaction can proceed on a bare Rh metal surface, and the
modification with ReOx makes the surface of Rh ensemble
smaller by the attachment of ReOx and the reaction is
inhibited on the small Rh ensemble. The much higher reactivity
of tetrahydrofurfuryl alcohol than tetrahydrofuran suggests
that the hydrogenolysis of tetrahydrofurfuryl alcohol can be
strongly assisted by the interaction of the –CH2OH group in
tetrahydrofurfuryl alcohol with Rh–ReOx/SiO2, since it has
been known that adsorbed methoxy species is formed by the
interaction between methanol and ReOx.15
Notes and references
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Furthermore, the hydrogenolysis of tetrahydropyran-2-
methanol was tested (Table 1, entries 12, 13). This is because
the chemical structure of tetrahydropyran-2-methanol is analo-
gous to that of tetrahydrofurfuryl alcohol. Tetrahydropyran-
2-methanol can be synthesized by hydrogenation of acrolein
dimer,3 and acrolein dimer will be produced by the dimerization
of acrolein using Diels–Alder reaction,16 and acrolein is given
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Chem. Commun., 2009, 2035–2037 | 2037