Liquid phase hydrogenation of methyl levulinate over the mixture of supported ruthenium catalyst and zeolite in water

Article abstract of DOI:10.1016/j.apcata.2013.10.059

Liquid-phase hydrogenation of methyl levulinate was studied over graphite-supported ruthenium (Ru/graphite), zeolite-supported ruthenium, and a mixture of Ru/graphite and zeolites in water at 343 K. The final γ-valerolactone yield over the mixture of Ru/graphite and ZSM-5 showed the highest activities between Ru/graphite, Ru/ZSM-5, and the mixture of Ru/graphite and several zeolites. Methyl levulinate was hydrogenated to methyl 4-hydroxyvalerate or directly to γ-valerolactone over supported ruthenium metal sites and methyl 4-hydroxyvalerate was converted to γ-valerolactone over acid sites. The mixture of Ru/graphite and ZSM-5 contained both highly dispersed ruthenium metal particles and a number of acid sites rather than those over zeolite-supported ruthenium catalysts, which led to the highest γ-valerolactone yield.

Full text of DOI:10.1016/j.apcata.2013.10.059

Applied Catalysis A: General 470 (2014) 215–220
Contents lists available at ScienceDirect
Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
Liquid phase hydrogenation of methyl levulinate over the mixture of
supported ruthenium catalyst and zeolite in water
Jayprakash M. Nadgeri, Norihito Hiyoshi, Aritomo Yamaguchi,
Osamu Sato, Masayuki Shirai∗
Research Center for Compact Chemical System, National Institute of Advanced Industrial Science and Technology (AIST), 4-2-1 Nigatake, Miyagino, Sendai
983-8551, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 14 July 2013
Received in revised form 18 October 2013
Accepted 28 October 2013
Available online 5 November 2013
Liquid-phase hydrogenation of methyl levulinate was studied over graphite-supported ruthenium
(Ru/graphite), zeolite-supported ruthenium, and a mixture of Ru/graphite and zeolites in water at 343 K.
The final ␥-valerolactone yield over the mixture of Ru/graphite and ZSM-5 showed the highest activities
between Ru/graphite, Ru/ZSM-5, and the mixture of Ru/graphite and several zeolites. Methyl levulinate
was hydrogenated to methyl 4-hydroxyvalerate or directly to ␥-valerolactone over supported ruthe-
nium metal sites and methyl 4-hydroxyvalerate was converted to ␥-valerolactone over acid sites. The
mixture of Ru/graphite and ZSM-5 contained both highly dispersed ruthenium metal particles and a num-
ber of acid sites rather than those over zeolite-supported ruthenium catalysts, which led to the highest
␥-valerolactone yield.
Keywords:
Liquid phase hydrogenation
Supported ruthenium catalyst
␥-Valerolactone
© 2013 Elsevier B.V. All rights reserved.
Graphite support
1. Introduction
␥-valerolactone at 473 K [27] and 403 K [28], respectively. We have
previously reported that a graphite-supported ruthenium catalyst
Petroleum is a limited resource and the use of renewable sources
for chemicals is inevitable; biomass from the plant material is
becoming an increasingly important option [1]. Lignocellulose,
which contains cellulose, hemicellulose, and lignin, can be con-
verted into valuable chemicals by several chemical conversions
such as thermal decomposition, acid hydrolysis, isomerization,
and hydrogenation [2–8]. ␥-Valerolactone is a platform chemi-
cal for functional polymer synthesis, gasoline blending, solvents,
etc. [9–15] and can be obtained by hydrogenation of levulinic acid
[16–24], which can be obtained from the hydrolysis of cellulose
over acid catalysts in water [25]. During hydrolysis, the leaching of
active metal species by the formation of metal–carboxylate com-
plexes with levulinic acid is unpreventable. To overcome this metal
leaching issue, an alternative route using levulinic ester, which
is obtained by alcoholysis of cellulose over acid catalysts, can be
performed [26].
showed complete hydrogenation to methyl levulinate at 343 K with
the addition of levulinic acid [29]. The liquid-phase hydrogenation
of methyl levulinate proceeds in two paths: (1) direct hydrogena-
tion to ␥-valerolactone and (2) hydrogenation of carbonyl groups
to methyl 4-hydroxyvalerate, following to the dealcoholization
of methyl 4-hydroxyvalerate to ␥-valerolactone (Scheme 1). The
dealcoholization step is critical for high ␥-valerolactone yield,
which can be accelerated by high temperature or acid co-catalysts
and zeolites are expected to be suitable acid co-catalysts.
In this manuscript, we report that zeolites are useful for the
dealcoholization step of methyl levulinate for low-temperature
hydrogenation and activities of the mixture of graphite-supported
ruthenium metal catalysts and HZSM-5 are higher than those of
zeolite-supported ruthenium catalysts.
2. Experimental
There are a few reports of the hydrogenation of methyl
levulinate to ␥-valerolactone using heterogeneous catalysis.
Rode’s group reported that zirconia-supported copper and
charcoal-supported ruthenium catalysts were active for the hydro-
genation of methyl levulinate, showing 90% and 87% yields of
2.1. Materials
Methyl levulinate was purchased from TCI. Aqueous ruthe-
nium(III) nitrosyl nitrite solution (1.5 wt% of ruthenium), and
Amberlyst-15® were purchased from Wako Pure Chemicals
Industries Ltd. Graphite powder (HSAG300) was purchased from
TIMCAL Ltd. All chemicals were used without purification. Two
types of HZSM-5 having SiO2/Al2O3 ratios of 30 and 60, denoted as
∗
Corresponding author. Tel.: +81 22 237 5224; fax: +81 22 237 5219.
E-mail address: m.shirai@aist.go.jp (M. Shirai).
0926-860X/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.apcata.2013.10.059

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J.M. Nadgeri et al. / Applied Catalysis A: General 470 (2014) 215–220
OH
(a)
O
3
2
1
0
H2
O
Ru
O
O
H+
O
H2
Ru
O
O
+ CH3OH
(b)
Scheme 1. Liquid phase hydrogenation of methyl levulinate.
3
2
1
0
HZSM-5(30) and HZSM-5(60), respectively, were purchased from
JGC Catalyst and Chemicals Ltd. Two types of USY-type zeolites
having SiO2/Al2O3 ratios of 12 and 5.9, denoted as USY(12) and
USY(5.9), respectively, were purchased from UOP. ␤-Zeolites
having SiO2/Al2O3 ratios of 25, denoted as ␤-zeolite(25), was also
purchased from UOP.
2.2. Catalyst preparation
0
1
2
3
4
Zeolite samples were calcined at 773 K for 5 h before use. Sup-
ported ruthenium catalysts were prepared by an impregnation
method using an aqueous ruthenium(III) nitrosyl nitrite solution
and HSAG300 or zeolite, followed by the treatment in a flow of
hydrogen at 573 K for 2 h [29]. Catalysts are denoted by the amount
of ruthenium metal and support; e.g., 1.0Ru/graphite means the
sample of 1.0 wt% of ruthenium metal supported on graphite.
Reaction time/ h
Fig. 1. Reaction profile for the hydrogenation of 3.25 mmol of methyl levulinate
under 3 MPa of hydrogen at 343 K over (a) 0.025 g of 1.0Ru/graphite and (b) 0.025 g
of 0.2Ru/graphite in 10 mL of water. Methyl levulinate (ꢀ), methanol (ꢁ), ␥-
valerolactone (ꢀ), and methyl 4-hydroxyvalerate (ꢁ).
3. Result and discussion
2.3. TEM analysis
3.1. Hydrogenation activity
TEM measurements of the samples were performed on an FEI
TECNAI G20 (200 keV).
Fig. 1(a) shows the reaction profile for the hydrogenation
of 3.25 mmol of methyl levulinate under 3 MPa of hydrogen
at 343 K over 1.0Ru/graphite in 10 mL of water. At 10 min, all
methyl levulinate was consumed with the formation of 2.19 mmol
of methyl 4-hydroxyvalerate (68% selectivity) and 1.02 mmol of
␥-valerolactone (32% selectivity). The stoichiometric equivalent
amount of methanol to ␥-valerolactone was also obtained. Upon
complete consumption of methyl levulinate, the amount of methyl
4-hydroxyvalerate decreased slowly with a marginal increase in
␥-valerolactone yield, indicating that dealcoholization of methyl
4-hydroxyvalerate to ␥-valerolactone proceeded slowly in water
at 343 K. Fig. 1(b) shows the reaction profile for the profile for the
hydrogenation of methyl levulinate over 0.2Ru/graphite in water.
At 10 min, most of methyl levulinate was consumed and 2.24 mmol
of methyl 4-hydroxyvalerate (70% of selectivity) and 0.97 mmol
of ␥-valerolactone (30% of selectivity) were formed. An equiva-
lent amount of methanol to ␥-valerolactone was also obtained.
Similar to the results over 1.0Ru/Graphite, the dealcoholization of
methyl 4-hydroxyvalerate proceeded slowly to ␥-valerolactone in
water. We confirmed that no ruthenium species existed in water
after the hydrogenation over Ru/graphite by ICP analysis. Also,
2.4. Hydrogenation of methyl levulinate
The hydrogenation activities were studied with a batch system.
The weighed amounts of the solid catalyst, methyl levulinate, and
water were placed in a stainless steel high-pressure reactor (50 cm3
capacity), and the reactor was flushed three times with 3 MPa of
argon. Once the required temperature was attained in an oil bath,
hydrogen was introduced into the reactor at the desired pressure
(3 MPa), then the suspension in the vessel was stirred, which was
deemed the start of the reaction. Upon completion of the reaction,
the reactor was cooled rapidly in an ice bath. The pressured gas
was released slowly, and the contents were discharged to separate
the catalyst by filtration. The unreacted methyl levulinate and the
reaction products were recovered with acetone, which showed a
material balance of more than 95% as per stoichiometry.
The quantitative analysis of liquid samples was performed by
gas chromatography (HP-6890), equipped with flame ionization
detector and a DB-WAX capillary column. The conversion, yield,
and selectivity were defined as follows:
Conversion
%
= (1 − amount of methyl levulinate unreacted mol / amount of methyl levulinate introduced mol × 100,
)) ))
( )
(
(
(
(
Yield
%
( )
=
the amount of each product obtained mol / amount of methyl levulinate introduced mol × 100,
)) ))
(
(
(
(
Selectivity % = the amount of each product obtained mol / amount of methyl levulinate consumed mol × 100.
( ) )) ))
(
(
(
(

J.M. Nadgeri et al. / Applied Catalysis A: General 470 (2014) 215–220
217
3
2
1
0
3
2
1
0
0
1
2
3
4
0
1
2
3
4
Reaction time/ h
Reaction time/ h
Fig. 2. Reaction profile for the hydrogenation of 3.25 mmol of methyl levulinate
under 3 MPa of hydrogen in 10 mL of water at 343 K over 0.025 g of 0.2Ru/HZSM-5
in 10 mL of water. Methyl levulinate (ꢀ), methanol (ꢁ), ␥-valerolactone (ꢀ), and
methyl 4-hydroxyvalerate (ꢁ).
Fig. 3. Reaction profile for the hydrogenation of 3.25 mmol of methyl levulinate
under 3 MPa of hydrogen in 10 mL of water at 343 K over the mixture of 0.025 g
of 0.2Ru/graphite and 0.025 g of HZSM-5(30). Methyl levulinate (ꢀ), methanol (ꢁ),
␥-valerolactone (ꢀ), and methyl 4-hydroxyvalerate (ꢁ).
we separately verify by the following experiment that no ruthe-
nium species leached. After the treatment of methyl levulinate
over Ru/graphite in water under argon atmosphere, we recovered
the aqueous solution. We treated the recovered aqueous solution
under 3 MPa of hydrogen at 343 K and confirmed that no hydro-
genation proceeded. Fig. 1 shows that Ru/graphite catalysts were
active for the hydrogenation of methyl levulinate even at 0.2wt%
ruthenium loading and that the selectivity of direct hydrogenation
to ␥-valerolactone over 0.2Ru/graphite was almost the same as that
over 1.0Ru/graphite. It is reported that the cyclization of methyl
levulinate over Ru/C proceeded thermally at high reaction temper-
ature as 403 K [26]; however, the result of Fig. 1 shows that the
dealcoholization of methyl 4-hydroxyvalerate is critical for high
yields of ␥-valerolactone at low reaction temperature as 343 K.
Fig. 2 shows the reaction profile for the hydrogenation of
methyl levulinate under 3 MPa of hydrogen in water at 343 K
over 0.2Ru/HZSM-5(30). At 10 min, 0.77 mmol of methyl levuli-
nate (24% conversion) were consumed with the formation of
0.41 mmol of methyl 4-hydroxyvalerate (53% of selectivity) and
0.36 mmol ␥-valerolactone (47% selectivity), indicating that the
hydrogenation activity of 0.2Ru/HZSM-5(30) was much lower than
0.2Ru/graphite. At 1 h, 2.13 mmol of methyl levulinate (66% of
conversion) were consumed with the formation of 0.74 mmol of
methyl 4-hydroxyvalerate (35% selectivity) and 1.38 mmol (65%
selectivity) of ␥-valerolactone and methanol. After 1 h, the yield
of methyl 4-hydroxyvalerate decreased with the reaction time,
indicating that the dealcoholization of methyl 4-hydroxyvalerate
proceeded by the acidity of HZSM-5 support. Finally, 3.12 mmol of
␥-valerolactone (96% conversion) were obtained after 4 h.
Fig. 3 shows the reaction profile for the hydrogenation of methyl
levulinate over the mixture of 0.2Ru/graphite and HZSM-5(30);
2.13 mmol of methyl levulinate (65% of conversion) was hydro-
genated and 1.26 mmol of 4-hydroxy levulinate (59% of selectivity)
and 0.87 mmol of ␥-valerolactone (41% of selectivity) were formed
at 10 min. Complete methyl levulinate consumption was achieved
with the formation of 1.75 mmol of methyl 4-hydroxyvalerate (54%
of yield) and 1.50 mmol of ␥-valerolactone (46% of yield) at 30 min.
Furthermore, the dealcoholization of methyl 4-hydroxyvalerate
proceeded with the formation of 3.22 mmol of ␥-valerolactone
(99% yield) over the mixture of 0.2Ru/graphite and HZSM-5(30),
which was higher than that of 0.2Ru/HZSM-5(30). The mixture of
0.2Ru/graphite and HZSM-5(30) had both highly active ruthenium
sites for hydrogenation and acid sites for dealcoholization, resulting
in high yield of ␥-valerolactone. The order of final ␥-valerolactone
yield values was as follows: the mixture of 0.2Ru/graphite and
HZSM-5 > 0.2Ru/HZSM-5 > 0.2Ru/graphite.
For studying the effect of the acidity of zeolites, we investigated
the hydrogenation activities of the mixture of 1.0Ru/graphite and
several kinds of zeolites (Fig. 4). To compare the dealcoholization
activity of several zeolites under conditions that the hydrogena-
tion of methyl levulinate to methyl 4-hydroxyvalerate has been
finished, we used the 1.0Ru/graphite catalyst that was much active
for hydrogenation of methyl levulinate to 4-hydroxyvalerate than
0.2Ru/graphite.
The formation of ␥-valerolactone stopped over Ru/graphite
(Fig. 1); however, the addition of solid acid catalysts to Ru/graphite
enhanced the formation of ␥-valerolactone from methyl 4-
hydroxyvalerate. The order of the enhancement of formation rate
and final yield of ␥-valerolactone was as follows: HZSM-5(30) > ␤-
zeolite(25) > HZSM-5(60) > Amberlyst-15> USY(12) > USY(5.9). Gal-
letti et al. reported that the addition of Amberlyst-15 enhanced
the ␥-valerolactone yield in the liquid-phase hydrogenation of
levulinic acid over a charcoal-supported ruthenium catalyst [21].
The result in Fig. 4 shows that HZSM-5 and ␤-type zeolites were
more effective for dealcoholization of methyl 4-hydroxyvalerate
than Amberlyst-15. We have reported that the addition of levulinic
acid enhanced the ␥-valerolactone yield for the hydrogenation of
methyl levulinate over Ru/graphite at 343 K [29]; however, the
complete dealcoholization of methyl 4-hydroxyvalerate was not
obtained after 4 h at 343 K. These results indicate that the com-
bination of Ru/graphite and ZSM-5 is the best for the complete
(g)
(f)
3
2
1
0
(e)
(d)
(c)
(b)
(a)
0
1
2
3
4
Reaction time/ h
Fig. 4. Amount of ␥-valerolactone obtained over 0.025 g of 1.0Ru/graphite (ꢁ) (a),
and mixture of 0.025 g of 1.0Ru/graphite and 0.025 g of USY-5.9(ꢁ) (b), USY-12(ꢀ)
(c), Amberlyst-15 (ꢂ) (d), HZSM-5(60) (ꢃ) (e), ␤-zeolite(25) (ꢄ) (f), and HZSM-5(30)
(ꢀ) (g). Methyl levulinate: 3.25 mmol, hydrogen pressure: 3 MPa, solvent: 10 mL
water, reaction temperature: 343 K.

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J.M. Nadgeri et al. / Applied Catalysis A: General 470 (2014) 215–220
Fig. 5. TEM images and histogram of ruthenium metal particles of 0.2Ru/graphite and 0.2Ru/HZSM-5(30).
transformation of methyl levulinate to ␥-valerolactone at 343 K.
Fig. 4 also shows that zeolites having lower SiO2/Al2O3 ratios had
higher ␥-valerolactone yields between zeolites of the same struc-
ture, indicating that the number of acid sites is also important. The
effect of acid sites will be discussed later.
4-hydroxyvalerate and ␥-valerolactone at the initial stage. One
probable explanation for higher initial hydrogenation rates of
Ru/graphite than those over Ru/HZSM-5(30) is that small ruthe-
nium particles on graphite could provide larger amounts of
accessible surface ruthenium sites for methyl levulinate than those
of ruthenium metal particles in zeolite pores.
3.2. Ruthenium metal sites for hydrogenation of methyl levulinate
3.3. Acid sites for dealcoholization of methyl 4-hydroxyvalerate
Fig. 5 shows TEM images of 0.2Ru/graphite and 0.2Ru/HZSM-
5(30) catalysts and the histogram of the ruthenium metal particles.
All catalysts prepared contained highly dispersed ruthenium
metal particles. TEM images show that ruthenium metal parti-
cles were located on graphite surfaces for Ru/graphite and in
micropores of zeolite supports for Ru/HZSM-5(30). The aver-
age ruthenium metal particle size depends upon the kind of
supports and was independent of the loading (Fig. 6): 1.3 nm
on graphite and 2.6 nm on HZSM-5. From the reaction profiles
(Figs. 1 and 2), the order of initial methyl levulinate consumption
rates over supported ruthenium catalysts (Ru/graphite > Ru/HZSM-
5(30)) matches the ruthenium metal particle size distributions
on supports (graphite > HZSM-5). Most of all methyl levulinate
molecules introduced was hydrogenated over 0.2Ru/graphite;
however, 24% conversion was obtained over Ru/HZSM-5 for 10 min
at 343 K. With the ruthenium metal dispersion values estimated
from the average size of ruthenium metal particles on graphite
(dispersion 90%) and HZSM-5 (45%), we estimated turnover num-
ber values for 0.2Ru/graphite and 0.2Ru/HZSM-5 were 7200 and
3500, respectively. Reaction profiles under the reaction condi-
tions show that methyl levulinate were hydrogenated to methyl
Fig. 7 shows the ␥-valerolactone yields for 1 h over the mixture
of 1.0Ru/graphite and several kinds of zeolites which are proton
forms. The number of protons on the zeolite was estimated to be
the same amounts of aluminum atoms in zeolite samples. HZSM-
5 was highly active for the second step of dealcoholization of
methyl 4-hydroxyluvulinate to ␥-valerolactone. Because the acid-
ity (strength of acid sites) of zeolite depends on the structure, the
degree of enhancement of ␥-valerolactone yield for zeolites hav-
ing similar SiO2/Al2O3 ratios but different structure was different.
Fig. 7 shows that the highest ␥-valerolactone yield was obtained
over the combination of 1.0Ru/graphite and HZSM-5(30) between
the mixture of 0.025 g of 1.0Ru/graphite and 0.020 g of zeolites. We
studied the ␥-valerolactone yields with HZSM-5(30) and HZSM-
5(60). Ammonia TPD analysis showed that the number of acid sites
in HZSM-5(30) was twice as that in HZSM-5(60). A linear relation
between ␥-valerolactone yield and the number of acid sites, which
was controlled by weight of HZSM-5 zeolites introduced and also
by using HZSM-5 zeolites having different SiO2/Al2O3 ratios, indi-
cating that the ␥-valerolactone formation rate was proportional to
the number of acid sites on HZSM-5.

J.M. Nadgeri et al. / Applied Catalysis A: General 470 (2014) 215–220
219
Fig. 6. TEM images and histogram of ruthenium metal particles of 1.0Ru/graphite and 1.0Ru/HZSM-5(30).
100
80
over acid sites. The highest ␥-valerolactone yield was obtained
over the mixture of graphite-supported ruthenium metal catalyst
and HZSM-5, because ruthenium metal sites on graphite surface
and acid sites of HZSM-5 were highly active for methyl levulinate
hydrogenation and dealcoholization of methyl 4-hydroxylevunate,
respectively.
60
40
20
0
Acknowledgement
This work was supported by Special Coordination Funds for
Promoting Science and Technology “Development of Sustainable
Catalytic Reaction System using Carbon Dioxide and Water”.
0
1
2
3
4
Number of proton/ 1019
Fig. 7. ␥-Valerolactone yields over 0.025 g of 1.0Ru/graphite (ꢁ), the mixture of
0.025 g of 1.0Ru/graphite and 0.020 g of USY(12) (ꢀ), USY(5.9) (ꢁ), amberlyst-15
(ꢂ), HZSM-5(60) (ꢃ), ␤-zeolite (ꢄ), HZSM-5(30) (ꢀ), and the mixture of 0.025 g
of 1.0Ru/graphite and 0.050 g of HZSM-5(60) (ꢅ) and 0.013 g of HZSM-5(30) (᭹).
Methyl levulinate: 3.25 mmol, hydrogen pressure: 3 MPa, solvent: 10 mL water,
reaction time: 1 h, reaction temperature: 343 K.
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