Hydrogenation of levulinic acid to γ-valerolactone by Ni and MoO x co-loaded carbon catalysts

Article abstract of DOI:10.1039/c4gc00735b

To develop a noble metal-free heterogeneous catalyst for liquid phase hydrogenation of levulinic acid to γ-valerolactone under H₂, we tested a series of base-metal (Ni, Co, Cu, and Fe) and metal oxides (Mo, V, and W oxides) co-loaded carbon (C) and Ni-loaded metal oxides for the reaction. Ni-MoO_x/C pre-reduced at 500 °C showed the highest activity and showed more than 300 times higher turnover number (TON) than previously reported noble metal-free catalysts. A structure-activity relationship study showed that the co-presence of metallic Ni⁰ species and partially reduced MoO₂ could be responsible for the high activity. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c4gc00735b

Green Chemistry
View Article Online
View Journal | View Issue
PAPER
Hydrogenation of levulinic acid to γ-valerolactone
by Ni and MoO co-loaded carbon catalysts
x
Cite this: Green Chem., 2014, 16,
899
3
a,b
a
a
Ken-ichi Shimizu,* Shota Kanno and Kenichi Kon
To develop a noble metal-free heterogeneous catalyst for liquid phase hydrogenation of levulinic acid to
γ-valerolactone under H , we tested a series of base-metal (Ni, Co, Cu, and Fe) and metal oxides (Mo, V,
and W oxides) co-loaded carbon (C) and Ni-loaded metal oxides for the reaction. Ni–MoO /C pre-
reduced at 500 °C showed the highest activity and showed more than 300 times higher turnover number
2
x
Received 25th April 2014,
Accepted 4th June 2014
(TON) than previously reported noble metal-free catalysts. A structure–activity relationship study showed
DOI: 10.1039/c4gc00735b
0
that the co-presence of metallic Ni species and partially reduced MoO
2
could be responsible for the
www.rsc.org/greenchem
high activity.
2
2
be reused 3 times. However, the turnover number (TON) and
the turnover frequency (TOF) of the noble metal-free catalysts
Introduction
To achieve sustainable production of chemicals, biomass- for LA reduction by H are generally 1–2 orders of magnitude
2
1
3–15
derived platform compounds should not compete with food lower than those of Ru-based heterogeneous catalysts.
for their feedstock. Levulinic acid (LA) has been identified as a There are no noble metal-free catalysts with activity compar-
key intermediate in converting non-food biomass into chemi- able to the Ru-based catalysts for the hydrogenation of LA to
1
–3
cals and fuels,
produced from lignocellulosic materials using a conventional Ni–MoO
hydrolysis process. LA can be transformed into various attrac- based heterogeneous catalysts
because it can be easily and economically GVL. We report herein the first noble metal-free catalysts,
x
/C, with TON comparable to previously reported Ru-
1
3–15
for the title reaction. A
tive chemicals. In particular, γ-valerolactone (GVL) has been structure–activity relationship study was also carried out to
proposed as one of the key components in biorefinery discuss the structure of the active Ni and Mo species.
1
–3
systems,
because it can be used as an intermediate of
4
4
chemicals (1,4-pentanediol, 2-methyltetrahydrofuran, and
adipic acid ), fuels and solvents. Recently, numerous papers
were published on the hydrogenation of LA to GVL using
heterogeneous
Since early screening studies
5
6
7
Experimental section
7
–26
27–32
or homogeneous
catalytic systems. Commercially available organic and inorganic compounds
1
0,12
demonstrated a higher (from Tokyo Chemical Industry and WAKO Pure Chemical
activity of noble metal catalysts than Ni catalysts, most of the Industries) were used without further purification. The GC
catalysts reported were based on noble metals (mainly Ru, Ir (Shimadzu GC-2014) and GCMS (Shimadzu GCMS-QP2010)
1
0–19,27–32
and Au).
For a practical application, homogeneous analyses were carried out with an Ultra ALLOY capillary
+
catalysts suffer from high costs of noble metals and ligands column UA -5 (Frontier Laboratories Ltd) using nitrogen as the
and difficulty in the catalyst/product separation. Hetero- carrier gas. Catalyst supports used in this study were as
geneous noble metal-based catalysts also suffer from high follows: carbon (Lion, Ketjenblack EC-600JD, 1310 m
2
−1
g ),
2
−1
costs. Thus, development of noble metal-free heterogeneous SiO (Fuji Silysia Chemical Ltd, Q-10, 300 m g ), MgO (Cata-
2
catalysts for this reaction is an important research target. lysis Society of Japan, CSJ, JRC-MGO-3), TiO (CSJ, JRC-TIO-4),
2
1
9–26
Recently, noble metal-free heterogeneous catalysts,
as supported Cu and Ni catalysts, were reported. For example, Catapal B Alumina, Sasol) at 900 °C for 3 h.
Cu–ZrO can be utilized to perform the reaction with complete
A precursor of the standard Ni–MoO /C catalyst with Ni
such CeO2 (CSJ, JRC-CEO-3), and γ-Al O (calcination of γ-AlOOH,
2
3
2
x
LA conversion and 90% selectivity to GVL, and the catalyst can loading of 10 wt% and Mo loading of 7 wt% was prepared by
the co-impregnation method; the support (carbon) and
(
NH ) Mo O ·4H O were added to aqueous solution of
4 6 7 24 2
a
Catalysis Research Center, Hokkaido University, N-21, W-10, Sapporo 001-0021,
Ni(NO
3
)
2
nitrates, followed by evaporation to dryness at 50 °C
co-loaded
Japan
b
and by drying at 90 °C for 12 h. Other Ni and MoO
Elements Strategy Initiative for Catalysts and Batteries, Kyoto University, Katsura,
x
Kyoto 615-8520, Japan. E-mail: kshimizu@cat.hokudai.ac.jp; Fax: +81-11-706-9163
catalysts (designated as Ni–MoO /support), Ni and MOy
x
This journal is © The Royal Society of Chemistry 2014
Green Chem., 2014, 16, 3899–3903 | 3899

View Article Online
Paper
Green Chemistry
y
co-loaded carbon (Ni–MO /C, M = 7 wt% V, W) with Ni loading
of 10 wt% and metal and MoO co-loaded catalysts (M′–MoO /
x
x
C, M′ = 10 wt% Ni, Cu, Co, Fe) with Mo loading of 7 wt% were
prepared by the same method using metal nitrates (Ni, Cu, Co
or Fe) and ammonium salts of M, (NH ) Mo O ·4H O,
4
6
7
24
2
NH
Ni/support) were prepared by the impregnation method using
aqueous solution of Ni(NO ) . Before each catalytic experi-
4 3 4 10 12 2
VO or (NH ) W O41·5H O. 10 wt% Ni loaded catalysts
(
3
2
ment, these catalyst precursors were pre-reduced in a pyrex
3
−1
2
tube under a flow of H (20 cm min ) at 500 °C for 0.5 h and
were used for the reaction without exposure to air.
X-ray diffraction (XRD) patterns of the powdered catalysts
were recorded with a Rigaku MiniFlex II/AP diffractometer
with Cu Kα radiation. The X-ray photoelectron spectroscopy
Fig. 1 Catalytic activity of Ni–MoO
solvent-free and low catalyst loading (0.02 mol% Ni) conditions versus
catalyst reduction temperature.
x
/C for hydrogenation of LA under
(XPS) measurements were carried out using
a
JEOL
JPS-9010MC with a Mg Kα anode operated at 20 W and 10 kV.
The binding energy was calibrated with respect to the C 1s
peak of the contaminated carbon (285.0 eV).
nic acid (1 mmol, 0.116 g) and n-dodecane (0.05 g) was
injected into the pre-reduced catalyst inside the glass tube
through the septum inlet. Then, the septum was removed
under air, and a magnetic stirrer was put in the tube, followed
by inserting the tube into a stainless autoclave with a dead
x
For the catalytic tests in Tables 1 and 2, Ni–MoO /C (10 wt%
Ni, 7 wt% Mo) pre-reduced at 500 °C was used as a standard
catalyst. After the pre-reduction, the catalyst (5.8 mg) in the
closed glass tube sealed with a septum inlet was cooled to
3
space of 28 cm . Soon after being sealed, the reactor was
room temperature under a H atmosphere. A mixture of levuli-
2
flushed with H from a high pressure gas cylinder and charged
2
2
with H (2 bar) at room temperature. Then, the reactor was
Table 1 Hydrogenation of LA to GVL by various catalysts
heated at 140 °C under stirring (150 rpm). For gram-scale cata-
lytic tests in Fig. 1 and Table 3, 50 bar H was charged to the
2
reactor containing a mixture of LA (20 mmol, 2.322 g),
n-dodecane (0.05 g) and 2.3 mg of Ni–MoO
Mo) pre-reduced at 500 °C, and the reactor was heated at
50 °C for 24 h. The conversion and yields of products were
determined by GC using n-dodecane as an internal standard.
The products were identified by GC-MS equipped with the
same column as GC and by comparison with commercially
available pure products.
x
/C (10 wt% Ni, 7 wt%
2
Entry
Catalysts
MoO /C
Conv. (%)
Yield (%)
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
x
0
100
64
59
50
38
14
15
7
18
8
18
12
38
5
0
97
64
59
50
38
14
10
1
5
8
11
0
38
5
Ni–MoO
Ni–MoO
Ni–MoO
Ni–MoO
x
x
x
x
/C
/SiO
/Al
/TiO
2
O
2
3
2
Ni–VO
Ni–WO
x
/C
/C
x
Ni/C
Results and discussion
Catalytic study
Ni/MoO
Ni/CeO
Ni/SiO
Ni/Al
Ni/MgO
Ni/TiO
Cu–MoO
Co–MoO
Fe–MoO
x
1
1
1
1
1
1
1
1
2
2
O
2 3
We studied the influence of various catalyst parameters on the
catalytic activity for hydrogenation of LA to γ-valerolactone
2
(
GVL) under solvent-free conditions in 8 bar H
5 h in the presence of 1 mol% of the supported metal catalysts
Table 1). First, we tested a series of 10 wt% Ni-loaded catalysts
2
at 140 °C for
x
/C
/C
x
1
0
1
0
x
/C
(
pre-reduced at 500 °C (entries 2–14). Generally, the Ni and
MoOx co-loaded catalysts (entries 2–5) showed higher yield
Table 2 Hydrogenation of LA to GVL by Ni–MoO
solvents
x
/C in various
(50–97%) than the conventional Ni-loaded metal oxides
entries 9–14, 0–38% yield). The Ni/C co-loaded with Mo, V,
a
(
Solvents
Conv. (%)
Yield (%) and W oxides (entries 2, 6, and 7) showed higher GVL yield
than Ni/C (entry 8), and MoO
best co-catalyst. MoO /C (entry 1) was completely inactive, indi-
cating that the MoO does not catalyze the reaction. The effect
x
(entry 2) was found to be the
No solvent
Toluene
100
24
13
2
97
21
4
x
1
,4-Dioxane
O
x
H
2
2
x
of support material on the activity of Ni and MoO co-loaded
a
catalysts (entries 2–5) showed that carbon is the best support.
LA (1 mmol) in 0 or 2 g solvent, 8 bar H
40 °C, 5 h.
2
, 6 mg catalyst (1 mol% Ni),
1
In a series of metals (Ni, Cu, Co, Fe) loaded on MoO /C
x
3900 | Green Chem., 2014, 16, 3899–3903
This journal is © The Royal Society of Chemistry 2014

View Article Online
Green Chemistry
Paper
Table 3 Heterogeneous catalysts for hydrogenation of LA to GVL by H
2
Catalyst
mol%
Solvent
2
P(H )/bar
T/°C
t/h
Yield (%)
TON
Ref.
Cu–CrO
x
6.4
10
0.029
0.02
0.02
0.02
Water
Methanol
Dioxane
Solvent-free
Solvent-free
Solvent-free
70
34
40
50
50
50
200
200
200
250
250
250
4
5
4
24
24
24
91
90
98
99
3
14
9
3400
4950
150
100
21b
22
15
This study
This study
This study
Cu–ZrO
Ru/TiO
2
2
Ni–MoO
Ni/C
Ni/HZSM5
x
/C
a
2
a
Ni content in Ni/HZSM5 was 30 wt%.
(
entries 2, 15–17), Ni–MoO /C showed the highest yield. To effective heterogeneous catalysts in terms of TON. Table 3
x
optimize the Mo content in Ni–MoO
different Mo contents (3, 7, 10, and 30 wt%) were also tested Ru/TiO
for the reaction, and it was found that the Ni–MoO /C catalyst comparable to the state-of-the-art catalysts for LA reduction to
x
/C catalysts, catalysts with demonstrates that Ni–MoO
x
/C shows high TON comparable to
1
5
2
.
This is the first noble metal-free catalyst with TON
x
with Mo content of 7 wt% gives the highest yield of GVL GVL. However, the TON of Ni–MoO
result not shown). Table 2 shows the effect of solvent on the homogeneous catalysis of a Ir pincer complex under basic con-
activity of Ni–MoO /C for hydrogenation of LA. Clearly, ditions, which showed 71% yield of GVL with 0.001 mol% of
x
/C is lower than that of a
(
x
3
0
the solvent-free conditions gave the highest yield of GVL. After the catalyst, corresponding to a TON of 71 000.
the reaction, the catalyst was easily separated from the reaction
mixture by a filtration. The filtered catalyst was washed with
Structure–activity relationship
acetone, followed by drying in air at 90 °C for 1 h, and by redu- On the basis of the spectroscopic characterization results, we
cing in H at 500 °C for 0.5 h. The recovered catalyst showed discuss the structure of active Ni and MoOx species in
2
lower yield of GVL (50%) than the first cycle (97%).
x
Ni–MoO /C (pre-reduced at 500 °C). A reference catalyst, NiO–
Fig. 1 shows the effect of pre-reduction temperature of the MoO /C, prepared by calcination of the catalyst precursor in
3
standard Ni–MoO /C catalyst (Mo = 7 wt%) on its activity for air at 300 °C was completely inert for LA reduction (result not
x
the gram-scale hydrogenation of 20 mmol LA in 50 bar H at shown). When the standard Ni–MoO /C catalyst pre-reduced at
2
x
200 °C for 24 h under low catalyst loading conditions (0.02 mol% 500 °C was exposed to air at room temperature for 0.5 h, the
Ni with respect to LA). The activity showed a volcano-type catalyst showed lower yield (55%) than the standard catalyst
0
dependence on the reduction temperature, and the catalyst (99%). This suggests that the metallic Ni species on the surface
reduced at 500 °C gave the highest activity. From these results, of Ni metal particles are the active species and re-oxidation of
we fixed the solvent-free system with the Ni–MoO /C catalyst them results in a decrease in the activity, probably due to a
x
0
(
Ni = 10 wt%, Mo = 7 wt%) reduced at 500 °C as the most decrease in the amount of surface Ni species. Fig. 2 shows the
effective catalytic system for the LA reduction.
XRD patterns of the catalyst after various reduction tempera-
Next, we discuss the performance of the present system in tures. The catalyst pre-reduced at 300 °C showed diffraction
comparison with the previous catalysts. The most important lines due to Ni metal and NiO, and the catalyst showed rela-
aspect of this catalytic system is high TON. As shown in Fig. 1 tively low activity (Fig. 1). The catalysts reduced at higher temp-
and Table 3, 20 mmol LA were nearly quantitatively converted eratures (500 °C and 600 °C) showed no lines due to NiO but
to GVL by 2.3 mg (0.02 mol%) of Ni–MoO /C at 250 °C in 24 h, lines due to metallic Ni. The lines due to the metallic Ni shift
x
corresponding to TON of 4950 and TOF of 206 h− (with
1
respect to the total number of Ni atoms in the catalyst),
3
3
respectively. As compared in Table 3, this TON value is more
than 300 times larger than those of previously reported non-
noble metal catalysts. Recently, Ni/HZSM5 with Ni content of
3
0 wt% has been reported as an effective catalyst for vapor
2
3
2
phase hydrogenation of LA by H to GVL. We prepared
Ni/HZSM5 by the similar method and tested for the liquid
phase LA reduction. As listed in Table 3, Ni/HZSM5 showed
2
3
2
% yield of GVL. Under the same reaction conditions,
Ni–MoO /C showed about 50 times higher TON than
x
−
1
Ni/HZSM5. Note that TOF of Ni–MoO /C (206 h ) is two
x
orders of magnitude higher than that of Ni/ZSM5 in the litera-
ture for vapor phase LA reduction to GVL at 250 °C (TOF =
−
1 23
1
.8 h ). By a comparison with the literature data, Ru cata-
Fig. 2 XRD patterns of the Ni–MoO
have been identified as the most various temperatures.
x 2
/C after pre-reduction by H at
1
5
2
lysts, especially Ru/TiO ,
This journal is © The Royal Society of Chemistry 2014
Green Chem., 2014, 16, 3899–3903 | 3901

View Article Online
Paper
Green Chemistry
Notes and references
1
2
3
4
5
6
7
8
9
M. J. Climent, A. Corma and S. Iborra, Green Chem., 2014,
6, 516–547.
M. Besson, P. Gallezot and C. Pinel, Chem. Rev., 2013, 114,
827–1870.
T. Horváth, H. Mehdi, V. Fábos, L. Boda and L. T. Mika,
Green Chem., 2008, 10, 238–242.
1
1
X. Du, Q. Bi, Y. Liu, Y. Cao, H. He and K. Fan, Green Chem.,
2012, 14, 935–939.
S. Van de Vyver and Y. Román-Leshkov, Catal. Sci. Technol.,
2013, 3, 1465–1479.
Q. Bond, D. M. Alonso, R. M. West and J. A. Dumesic,
Science, 2010, 327, 1110–1114.
D. M. Alonso, S. G. Wettstein and J. A. Dumesic, Green
Chem., 2013, 15, 584–595.
W. R. H. Wright and R. Palkovits, ChemSusChem, 2012, 5,
3
Fig. 3 XPS spectra in Mo 3d5/2 and Ni 2p3/2 regions: (a) NiO–MoO /C
pre-oxidized at 300 °C in air for 3 h; Ni–MoO
b) 500 °C and (c) 600 °C.
x
/C pre-reduced at
(
to lower angle with an increase in the pre-reduction tempera-
ture, which suggests that the Mo atom, having larger size than
the Ni atom, is incorporated into Ni metal forming the Ni–Mo
alloy phase.
1
657–1667.
J. Zhang, S. Wu, B. Li and H. Zhang, ChemCatChem, 2012,
, 1230–1237.
4
To discuss the oxidation states of Ni and Mo species in the
catalysts reduced at 500 °C and 600 °C, we carried out an XPS
study (Fig. 3). As expected the oxidized reference sample,
NiO–MoO /C, showed a Ni 2p peak (855 eV) due to NiO and
1
1
0 E. Manzer, Appl. Catal., A, 2004, 272, 249–256.
1 R. A. Bourne, J. G. Stevens, J. Ke and M. Poliakoff, Chem.
Commun., 2007, 4632–4634.
3
3/2
3
4
1
1
1
1
2 Z. P. Yan, L. Lin and S. J. Liu, Energy Fuels, 2009, 23,
a Mo 3d5/2 peak (231.8 eV) due to MoO3. In contrast, the
Ni–MoO /C catalyst reduced at 500 °C showed a Ni 2p3/2 peak
852.4 eV) due to Ni metal and a Mo 3d5/2 peak (228.4 eV) due
to MoO with a weak shoulder peak at 227.9 eV due to Mo
3853–3858.
x
3 A. M. R. Galletti, C. Antonetti, V. D. Luise and
M. Martinelli, Green Chem., 2012, 14, 688–694.
4 G. Al-Shaal, W. R. H. Wrigt and R. Palkovits, Green Chem.,
(
2
4
3
metal. The catalyst reduced at 600 °C showed a Ni 2p3/2 peak
852.4 eV) due to Ni metal and a Mo 3d5/2 peak (227.9 eV) due
2012, 14, 1260–1263.
(
5 W. H. Luo, U. Deka, A. M. Beale, E. R. H. van Eck,
to Mo metal. Combined with the fact that the catalyst reduced
at 500 °C showed higher activity than that reduced at 600 °C,
we propose that the co-presence of metallic Ni and partially
P. C. A. Bruijnincx and B. M. Weckhuysen, J. Catal., 2013,
301, 175–186.
1
1
1
1
2
2
6 X. L. Du, L. He, S. Zhao, Y. M. Liu, Y. Cao, H. Y. He and
K. N. Fan, Angew. Chem., Int. Ed., 2011, 50, 7815–7819.
7 P. A. Son, S. Nishimura and K. Ebitani, RSC Adv., 2014, 4,
reduced MoO species is responsible for the highest activity of
the catalyst reduced at 500 °C.
2
10525–10530.
8 A. M. Hengne, A. V. Malawadkar, N. S. Biradar and
C. V. Rode, RSC Adv., 2014, 4, 9730–9736.
9 J. M. Tukacs, R. V. Jones, F. Darvas, G. Dibó, G. Lezsák and
L. T. Mika, RSC Adv., 2013, 3, 16283–16287.
Conclusions
We demonstrated an effective non-noble-metal catalyst,
Ni–MoO
acid to γ-valerolactone under H
x
/C, for the liquid phase hydrogenation of levulinic
, which showed more than 300
0 M. Chia and J. A. Dumesic, Chem. Commun., 2011, 47,
2
12233–12235.
times higher TON than previously reported non-noble-metal
catalysts. This is the first noble metal-free catalyst with TON
comparable to the state-of-the-art Ru catalyst for this reaction.
1 (a) P. P. Upare, J.-M. Lee, Y. K. Hwang, D. W. Hwang,
J.-H. Lee, S. B. Halligudi, J.-S. Hwang and J.-S. Chang,
ChemSusChem, 2011, 4, 1749–1752; (b) K. Yan, J. Liao,
X. Wu and X. Xie, RSC Adv., 2013, 3, 3853–3856.
A structure–activity relationship study showed that co-presence
0
of metallic Ni species and MoO
for the catalytic activity.
2
species can be responsible
2
2
2
2 A. M. Hengne and C. V. Rode, Green Chem., 2012, 14,
1064–1072.
3 V. Mohan, C. Raghavendra, C. V. Pramod, B. D. Raju and
K. S. R. Rao, RSC Adv., 2014, 4, 9660–9668.
4 V. Mohan, V. Venkateshwarlu, C. V. Pramod, B. D. Raju and
K. S. R. Rao, Catal. Sci. Technol., 2014, 4, 1253–1259.
Acknowledgements
This work was supported by a Grant-in-Aid for Scientific 25 J. Yuan, S. Li, L. Yu, Y. Liu, Y. Cao, H. He and K. Fan,
Research on Innovative Areas “Nano Informatics” (25106010) Energy Environ. Sci., 2013, 6, 3308–3313.
from JSPS and a MEXT program “Elements Strategy Initiative 26 J. Wang, S. Jaenicke and G. Chuah, RSC Adv., 2014, 4,
to Form Core Research Center”. 13481–13489.
3902 | Green Chem., 2014, 16, 3899–3903
This journal is © The Royal Society of Chemistry 2014

View Article Online
Green Chemistry
Paper
2
7 H. Mehdi, V. Fábos, R. Tuba, A. Bodor, L. T. Mika and 31 J. Deng, Y. Wang, T. Pan, Q. Xu, Q.-X. Guo and Y. Fu, Chem-
I. T. Horváth, Top. Catal., 2008, 48, 49–54. SusChem, 2013, 6, 1163–1167.
8 F. M. A. Geilen, B. Engendahl, A. Harwardt, W. Marquardt, 32 V. Fábos, L. T. Mika and I. T. Horváth, Organometallics,
2
J. Klankermayer and W. Leitner, Angew. Chem., Int. Ed.,
010, 49, 5510–5514.
9 J. M. Tukacs, D. Király, A. Strádi, G. y. Novodárszki,
2014, 33, 181–187.
2
33 After the reaction by the standard catalyst, ICP–AES ana-
lysis of the solution showed a low level of metal leaching
(0.14 ppm Ni and 0.59 ppm Mo).
2
Z. s. Eke, G. Dibó, T. Kégl and L. T. Mika, Green Chem.,
2
012, 14, 2057–2065.
0 W. Li, J.-H. Xie, H. Lin and Q.-L. Zhou, Green Chem., 2012,
4, 2388–2390.
34 C. D. Wagner, W. M. Riggs, L. E. Davis, J. F. Moulder and
G. E. Muilenberg, Handbook of X-ray Photoelectron Spectro-
scopy, Perkin-Elmer, Eden Prairie, MN, 1979.
3
1
This journal is © The Royal Society of Chemistry 2014
Green Chem., 2014, 16, 3899–3903 | 3903