Vapor-phase hydrogenation of levulinic acid to Γ-valerolactone over Cu-Ni bimetallic catalysts

Article abstract of DOI:10.1016/j.catcom.2017.04.018

Vapor-phase hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) was performed over SiO₂-supported Cu-Ni bimetallic catalysts with different Cu/Ni weight ratios under ambient H₂ pressure. Characterization of the catalysts was carried out using powder X-ray diffraction, temperature-programmed reduction and thermogravimetric analysis. In contrast to the monometallic catalysts i.e. Ni/SiO₂ and Cu/SiO₂, the Cu-Ni/SiO₂ bimetallic catalyst with a Cu/Ni weight ratio of 6/14 exhibits an excellent catalytic activity, and gave a GVL yield higher than 99% with a productivity of 1.64kg_GVLkg_cat.^?1h^?1 at 250°C and at a high WHSV of 1.65h^?1 for 50h.

Full text of DOI:10.1016/j.catcom.2017.04.018

Accepted Manuscript
Vapor-phase hydrogenation of levulinic acid to γ-valerolactone
over Cu-Ni bimetallic catalysts
Rei Yoshida, Daolai Sun, Yasuhiro Yamada, Satoshi Sato, Graham
J. Hutchings
PII:
DOI:
Reference:
S1566-7367(17)30141-3
doi: 10.1016/j.catcom.2017.04.018
CATCOM 5003
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
28 December 2016
1 March 2017
11 April 2017
Please cite this article as: Rei Yoshida, Daolai Sun, Yasuhiro Yamada, Satoshi Sato,
Graham J. Hutchings , Vapor-phase hydrogenation of levulinic acid to γ-valerolactone
over Cu-Ni bimetallic catalysts. The address for the corresponding author was captured
as affiliation for all authors. Please check if appropriate. Catcom(2017), doi: 10.1016/
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ACCEPTED MANUSCRIPT
Vapor-phasehydrogenationoflevulinicacidto γ-valerolactoneoverCu-Ni
bimetalliccatalysts
Rei Yoshidaa, Daolai Suna, Yasuhiro Yamadaa, Satoshi Satoa*, Graham J. Hutchingsb
a Graduate School of Engineering, Chiba University, Chiba, 263-8522, Japan
bCardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff CF10 3AT, UK
* Corresponding author. Tel. +81 43 290 3376; Fax: +81 43 290 3401
E-mail address: satoshi@faculty.chiba-u.jp (S. Sato)
A revised manuscript for the original paper submitted to the journal of Catal. Commun.

ACCEPTED MANUSCRIPT
Abstract:
Vapor-phase hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) was
performed over SiO2-supported Cu-Ni bimetallic catalysts with different Cu/Ni weight ratios
under ambient H2 pressure. Characterization of the catalysts was carried out using powder X-ray
diffraction, temperature programmed reduction and thermogravimetric analysis. In contrast to the
monometallic catalysts i.e. Ni/SiO2 and Cu/SiO2, the Cu-Ni/SiO2 bimetallic catalyst with a Cu/Ni
weight ratio of 6/14 exhibits an excellent catalytic activity, and gave a GVL yield higher than 99%
with a productivity of 1.64 kgGVL kgcat.-1 h-1 at 250oC and at a high WHSV of 1.65 h-1 for 50 h.
Keywords: levulinic acid, -valerolactone, hydrogenation, Cu-Nibimetallic catalyst.

ACCEPTED MANUSCRIPT
1. Introduction
The depletion of fossil fuel resources and the increasing global environmental problems
motivate the application of renewable biomass carbon resources for producing useful chemicals as
well as energy [1]. LA is a material derivable from cellulose and hemicellulose present in
lignocellulosic feedstocks [1,2], and has applications as a food flavoring agent and also as a
starting material for the production of pharmaceutical compounds. LA has high reactivity due to
the presence of both ketone and carboxyl groups, and LA is also an attractive platform molecule to
produce various compounds such as GVL, 2-methyltetrahydrofuran (MTHF) and 1,4-pentanediol
(1,4-PDO) [3]. Among these compounds, GVLis attractive because of its importance as a solvent
and an intermediate in the chemical industry [4].
The hydrogenation of LA into GVL has to date mostly been investigated in liquid-phase
reactions under high H2 pressure conditions [4]. Supported precious metal catalysts were applied
for the hydrogenation of LA into GVL in some previous reports. Manzer performed reactions over
active carbon-supported Ru, Ir, Pt, Rh, Re, and Pd catalysts [5]. Among these catalysts, Ru/C
showed the highest catalytic activity for GVL formation and a 97% yield of GVLwas obtained at
o
150 C and an H2 pressure of 55 bar. Non-noble metal such as Cu and Ni also showed high
activity for the GVLformation from LA [6-9], and a quantitative yield of GVLwas obtained over
Cu/ZrO2 or Cu/Al2O3 at 200oCunder 34 bar H2 pressure [6].
From a viewpoint of industrial application, a continuous process for GVL production is
attractive and the use of earth abundant non-noble metal-based catalysts is preferable. Continuous
vapor-phase hydrogenation of LA into GVL over non-noble metal-based catalysts has been
reported by several groups in recent years [10-16]. In the report of Mohan et al., Ni/SiO2 provided
-1 -1
a GVL productivity of 0.87 kgGVL kgcat. h with a GVL selectivity of 87% under ambient H2
pressure conditions [14]. In contrast to Ni/SiO2, Upare et al. reported a Cu/SiO2 catalyst, which
-1 -1
showed a lower GVL productivity of 0.51 kgGVL kg
h , while the selectivity to GVL was as
cat.
high as 99.9% [11]. Since Ni is active for the LA conversion and Cu is selective for the GVL
formation, we reasoned that the preparation of Ni-Cu bimetallic catalysts would be an effective
method for the efficient formation of GVL from LA.

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In this study, the hydrogenation of LA to GVL over Cu-Ni bimetallic catalysts has been
investigated using a fixed-bed down-flow reactor under ambient H2 flow conditions. A series of
Ni-Cu bimetallic catalysts supported on SiO2 with different Cu/Ni weight ratios were examined
and we show that the bimetallic catalysts give a superior performance when compared with the
monometallic Cuand Nicatalysts.
2. Experimental
2.1 Materials andcatalyst preparation
LA was purchased from Wako Pure Chemical Industries, Japan, and was used for the
catalytic reaction without further purification. SiO2 (CARiACT Q10 with mean pore diameters of
10 nm) was supplied by Fuji Silycia Chemical Ltd. Cu(NO3)2·3H2O and Ni(NO3)2·6H2O, which
were used as the precursors of the corresponding metals, were purchased from Wako Pure
Chemical Industries, Japan.
SiO2-supported metal catalysts were prepared by an incipient wetness impregnation method
using a solution with a prescribed amount of Cu and Ni nitrate dissolved in distilled water. The
weight percentages of metal in the support were calculated using the weight of Cu and Ni metal in
the calcined catalysts. Total metal loading on SiO2 was fixed at 20 wt.%. After impregnation, the
samples were dried (110 oC, 12 h) and calcined (300 oC, 3 h). Hereafter, the prepared catalysts are
expressed as xCu-yNi/SiO2, where x and y indicate the weight percentage of the Cu and Ni metals,
respectively. For example, 6Cu-14Ni/SiO2 indicates 6 wt.% Cuand 14 wt.% Niloaded onSiO2.
2.2 Catalytic reaction
Vapor-phase hydrogenation of LA was performed in a fixed-bed down-flow glass reactor
with an inner diameter of 17 mm at an ambient pressure of H2. Prior to the reaction, a catalyst
(0.250gor 1.00g) was placed in the catalyst bed and reduced in H2 flow at 300oC; although 400oC
was used for 20Ni/SiO2 for 1 h. LA was then fed through the top of the reactor at a liquid feed rate
-1
3
of 1.65 cm3 h together with H2 (30 cm min-1). The liquid effluents were collected in a dry
ice-acetone trap (-78 oC) every hour and were analyzed by a FID-GC (GC-14B, Shimadzu) with a

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60-m capillary column of TC-WAX (GL-Science, Japan). A GC-MS (QP5050A, Shimadzu) was
used for identification of the products in the effluent. n-Butanol was used as an internal standard.
2.3 Characterizationof catalysts
The XRD patterns of samples were recorded on a D8 ADVANCE (Bruker, Japan) using
Cu Kα radiation. The thermogravimetry (TG) analysis was performed using Thermoplus 8120E2
(Rigaku) under the conditions: sample weight, ca. 10 mg; the rate of temperature increment, 5 oC
o
min-1 from the room temperature to 900 C. Temperature-programmed reduction (TPR) was
conducted for characterizing the metal state of the prepared catalysts. The measurements were
performed in a mixed flow of H2/N2 (1/9, 10 cm3 min-1) with a heating rate of 5 oC min-1 and a
temperature range from 25 to 900 oC, and the details are described elsewhere [17].
3. Results anddiscussion
Before conducting the catalytic reactions, TPR analyses of the Cu, Ni, and Cu-Ni
bimetallic catalysts were performed. As shown in Fig. 1, 20Ni/SiO2 shows a broad signal at ca.
350 oC, while 20Cu/SiO2 and Cu-Ni bimetallic catalysts show a sharp signal at ca. 220 oC. It is
obvious that the existence of Cu can decrease the reduction temperature of NiO, indicating the
interaction between Ni and Cu metal. Spillover effect on Cu-Ni bimetallic catalysts has been
widely reported [18-20], therefore, it is considered that CuO is reduced to Cu, and the hydrogen
associated with Cu shifts to NiO by a spillover effect that leads to reduction of NiO. Based on the
TPR analysis, the reduction temperature of 20Cu/SiO2 and Cu-Ni/SiO2 catalysts was determined
o
o
to be 300 C, while that of 20Ni/SiO2 was determined to be 400 C. Fig. 2 shows the XRD
patterns of 20Ni/SiO2, 20Cu/SiO2 and 6Cu-14Ni/SiO2 catalysts after reduction. The diffraction
reflections observed at 43.5o and 50.4o are attributed to Cu metal, while the reflections observed at
44.5o and 51.8o are attributed to Ni metal. No reflections assigned to metal oxides were observed
in these catalysts, indicating that the metal oxides were successfully reduced to metal before the
reaction. No reflections assigned to Cu-Ni alloy were observed in the profile of 6Cu-14Ni/SiO2,
which suggests that Cu-Nialloy was either highly dispersed or not formed.

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O
O
-H2O
age
O
+H2
O
O
OH
O
Levulinic acid
(LA)
Angelica lactones
(ALs)
-Valerolactone
(GVL)
C-C cleav
O
O
Acetone
2-Butanone
Scheme 1 The major products in the hydrogenation of LA.
The hydrogenation of LA to GVL was conducted over Cu, Ni, and Cu-Ni bimetallic
catalysts with different Cu/Ni weight ratios in H2 flow with a flow rate of 30 ml min-1 at 250 oC
-1
and a WHSV of 6.60 h . Table 1 shows the reaction results in the initial 8 h where the conversion
and selectivity were averaged for 8 h. Scheme 1 shows the major products in the reactions. Except
for the 20Cu/SiO2 catalyst, the main product was GVL, and the by-products included acetone,
methyl ethyl ketone (MEK), and angelicalactones (ALs). The ALs included α-, β- and
γ-angelicalactone isomers. ALs were produced by the cyclodehydration of LA, while MEK and
acetone were the decompositionproducts ofLA.
In the report of Uprare et al., 5Cu/SiO2 gave a GVL selectivity of 99.9% at a WHSV of
0.513 h-1 under 1 MPa H2 pressure conditions [11], indicating Cu was selective for the formation
-1
of GVL under low WHSV conditions. However, in the present study at a high WHSV of 6.60 h
under ambient H2 flow conditions, SiO2-supported Cu catalyst showed a low GVL selectivity of
25.5%, but a high ALs selectivity of 57.1%. In a recent study of our group, it was found that SiO2
efficiently catalyzed the cyclodehydration of LA to ALs in the vapor phase at a temperature range
o
of 250-300 C [21]. Therefore, it is reasonable that the ALs are generated over SiO2 as an
intermediate, whereas the hydrogenation ability of Cu is insufficient to efficiently convert ALs to
GVL under ambient H2 pressure and high WHSV conditions. In order to confirm the speculation,

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-1
the reaction over 20Cu/SiO2 was performed at a low WHSV of 3.30 h : the conversion of LA
and the selectivity to GVL increased to 73.4% and 75.4%, respectively, while the selectivity to
ALs decreased to 9.9%. In contrast to 20Cu/SiO2, 20Ni/SiO2 gave a high conversion of 94.2%
with a high GVL selectivity of 92.2% and a low ALs selectivity of 0.3%. It is obvious that the
hydrogenation ability of Ni is higher than Cu. However, LA decomposition products such as
acetone, MEK and -butyrolactone were formed as by-products over 20Ni/SiO2 and this
decreased the observed selectivity to GVL. In the case of 20Cu/SiO2, however, no decomposition
product was detected, indicating the inactivity of Cu for the C-C cleavage of LA. The
SiO2-supported Cu-Ni bimetallic catalysts showed different catalytic activity depending on the
Cu/Ni weight ratio. Compared with 20Ni/SiO2, the Cu-Ni bimetallic catalysts with Cu loadings
lower than 8 wt.% showed both high LA conversions and GVL selectivities, indicating that the
activity of Ni was improved by the interaction with Cu. On the other hand, the Cu-Ni bimetallic
catalysts with high Cu/Ni weight ratios such as 14Cu-6Ni/SiO2 and 16Cu-4Ni/SiO2 gave
relatively low LA conversions. This is possibly caused by the relatively low hydrogenation
activity of Cu. The catalyst with a Cu/Ni weight ratio of 6/14 showed the best catalytic
performance, and provided a LA conversion of 99.1% with a high GVL selectivity of 99.2%.
Upare et al. also reported a vapor-phase hydrogenation of LA using Cu-Ni/SiO2 catalysts with a
total metal loading of 80 wt.%, and the reactions were performed at a WHSV of 0.512 h-1 using
formic acid as a hydrogen donor and 1,4-dioxane as the solvent [16]. The suitable Cu/Ni weight
ratio was determined to be 3/1, which is much different from the present results. This difference
could be attributed to the different totalmetal loadings as well as the different reaction conditions.
Fig. 3 shows the changes in LA conversion and GVL selectivity in the reactions over the
20Cu/SiO2, 20Ni/SiO2 and Cu-Ni/SiO2 with different Ni and Cu loadings. 20Cu/SiO2 showed low
conversions as well as a low stability: the conversion over Cu/SiO2 gradually decreased from
25.6% to 9.7% during 8 h. Since ALs easily polymerize to form coke [21], the catalytic
deactivation of 20Cu/SiO2 is considered to be attribed to the large amount of intemediate ALs due
to low hydrogenation ability of Cu. Cu-Ni/SiO2 bimetallic catalysts showed enhanced catalytic
activity compared to 20Cu/SiO2, while the catlytsts with large Cu contents still deactivated rapidly.

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In contrast to the Cu-rich catalysts, 20Ni/SiO2 and the Ni-rich catalyts showed relatively stable
catalytic activities. This inicates that the Ni component is responsible for the catalytic stability. On
the other hand, in the reactions over 4Cu-16Ni/SiO2 and 6Cu-14Ni/SiO2 catalysts, slight decrease
in converion was observed after 6 h. We further performed a long-run test using 6Cu-14Ni/SiO2 at
-1
a lower WHSV of 1.65 h (Fig. 4). The catalytic activity was stable during 50 h: the conversion
was maintained at 100% and the GVL selectivity gradually increased to 99.7% at time on stream
(TOS) of 25 h. It has to be mentioned that the WHSV of 1.65 h-1 in the present study is higher than
that reported inprevious studies [10-16].
In the LA hydrogenation, catalyst deactivation is confirmed (Fig. 3). In order to evaluate
the amount of coke deposited on the catalysts, TG analyses of fresh and used catalysts were
performed. Fig. S1 depicts TG profiles for the fresh and used 20Ni/SiO2, 6Cu-14Ni/SiO2, and
20Cu/SiO2. The reaction conditions for the used catalysts were the same as those shown in Table 1,
and the fresh catalysts were also reduced before the TG analysis. Because the TG analyses were
performed in air atmosphere, the weight increase in the profiles of fresh catalysts is attributed to
the oxidation of Cu and/or Ni metal to the corresponding metal oxide(s). The weight attributed to
coke was calculated by subtracting the weight loss of the fresh catalyst from that of the used one.
The weight of coke in 20Ni/SiO2, 6Cu-14Ni/SiO2, and 20Cu/SiO2 was found to be 3.2, 5.5, and
9.0 wt.%, respectively. This indicates that coke is easily accumulated on 20Cu/SiO2, but difficult
to be accumulated on the catalysts with high Ni loadings such as 20Ni/SiO2 and 6Cu-14Ni/SiO2.
As the 20Cu/SiO2 catalyst deactivated rapidly compared to both the 20Ni/SiO2 and
6Cu-14Ni/SiO2 catalysts, the formation of coke is considered to cause the catalytic deactivation
primarily.
Table 2 compares the reaction result in this study with those in the previous reports.
Although almost quantitative yields of GVL are obtained over Ru/C [10], Cu/SiO2 [11], and
Ni/TiO2 [15], the productivities of these catalysts are low. The highest GVL productivity in
previous reports is 0.91 kgGVL kgcat.-1 h-1 achieved over Ni/ZSM-5 [13], whereas the selectivity to
GVL is relatively low. In contrast, in the present study, 6Cu-14Ni/SiO2 gave GVL yield higher
than 99% with a high productivity of 1.64 kgGVL kgcat.-1 h-1 for 50 h.

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4. Conclusions
A 6Cu-14Ni/SiO2 catalyst gave a high activity for the hydrogenation of LA to GVL at
high WHSV conditions under ambient H2 pressure. The enhanced activity of Cu-Ni bimetallic
catalysts would be attributed to both inhibition of carbon accumulation by Ni and inhibition of LA
decomposition by Cu. In contrast to the catalysts in previous reports, the 6Cu-14Ni/SiO2 catalyst
exhibited high catalytic performance: GVL yield higher than 99% with a high productivity of 1.64
kgGVL kgcat.-1h-1 at 250 oC and a WHSV of1.65 h-1 for 50 h.
Acknowledgement
This research was partly supported by JST, Strategic International Collaborative Research
Program, SICORP.

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References
[1] A.J. Ragauskas, C.K.Williams, B.H. Davison, G. Britovsek, J. Cairney, C.A. Eckert, W.J.
Frederick Jr., J.P.Hallett, D.J. Leak, C.L. Liotta, J.R. Mielenz, R. Murphy, R. Templer, T.
Tschaplinski, Science 311 (2006) 484-489.
[2] S.W. Fitzpatrick, ACS Symp. Ser. 921(2006) 271-287.
[3] R.V. Christian Jr., H.D. Brown, R.M. Hixon, J. Am. Chem. Soc. 69 (1947) 1961-1963.
[4] K. Yan,Y. Yang, J. Chai, Y. Lu, Appl. Catal. B: Environ. 179 (2015) 292-304.
[5] L.E. Manzer, Appl. Catal. A: Gen. 272 (2004) 249-256.
[6] A.M. Hengne, C.V. Rode, GreenChem. 14 (2012) 1064-1072.
[7] K. Yan, A. Chen, Energy 28 (2013) 357-363.
[8] J. Yuan, S. Li, L. Yu, Y. Liu, Y. Cao, H. He, K. Fan, EnergyEnviron. Sci. 6 (2013) 3308-3313.
[9] K. Yan, A. Chen, Fuel 115 (2014) 101-108.
[10] P.P. Upare,J. Lee, D.W.Hwang, S.B. Halligudi, Y.K. Hwang, J. Chang, J. Ind. Eng. Chem.
17 (2011) 287-292.
[11] P.P. Uprare,J. Lee, Y.K.Hwang, D.W. Hwang, J. Lee, S.B. Halligudi, J.S. Hwang, J. Chang,
ChemSusChem 4 (2011) 1749-1752.
[12] B. Putrakumar, N. Nagaraju, V.P. Kumar, K.V.R.Chary, Catal. Today250 (2015) 209-217.
[13] V. Mohan, C. Raghavendra, C.V. Pramod, B.D. Raju, K.S.R. Rao, RSCAdv. 4 (2014) 9660-9668.
[14] V. Mohan, V. Venkateshwarlu, C.V. Pramod, B.D. Raju, K.S.R.Rao, Catal. Sci. Technol. 4
(2014) 1253-1259.
[15] V.V. Kumar, G. Naresh, M. Sudhakar,J.Tardio, S.K. Bhargava, A. Venugopal, Appl. Catal.
A: Gen. 505 (2015) 217-223.
[16] P.P. Upare, M.G. Jeong, Y.K. Hwang, D.H. Kim, Y.D. Kim, D.W. Hwang, U.H. Lee, J.S.
Chang, Appl. Catal. A: Gen. 491 (2015) 127-135.
[17] T. Nakayama, N. Ichikuni, S. Sato, F. Nozaki, Appl. Catal. A:Gen. 158 (1997) 185-199.
[18] Y. Yao, D.W. Goodman, J. Mol. Catal. A:Chem. 383-384(2014) 239-242.
[19] S.H. Pang, N.E. Love, J.W.Medlin, J. Phys. Chem. Lett. 5 (2014) 4110-4114.
[20] S. Srivastava, G.C. Jadeja, J. Parikh, J. Mol. Catal. A:Chem. 426 (2017) 244-256.

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[21] D. Sun, Y. Takahashi, Y. Yamada, S. Sato, Appl. Catal. A:Gen. 526 (2016) 62-69.

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Table 1 The hydrogention of LA to GVL over SiO2-supported Cu, Ni and Cu-Ni bimetallic
catalysts.
Conversion
/mol%
94.2
Selectivity/mol%
Acetone MEK
GVL yield
/mol%
86.8
Catalyst
GVL
92.2
98.2
97.9
99.2
99.3
98.3
99.0
96.6
25.5
75.4
ALs
0.3
0
others
4.7
20Ni/SiO2
0.6
0
0.3
0.3
0.4
0.2
0.2
0.1
0
4Cu-16Ni/SiO2
5Cu-15Ni/SiO2
6Cu-14Ni/SiO2
7Cu-13Ni/SiO2
8Cu-12Ni/SiO2
14Cu-6Ni/SiO2
16Cu-4Ni/SiO2
20Cu/SiO2
97.8
1.5
96.1
98.2
1.0
0.1
0.1
0.6
0.1
0.5
0
0
0.7
96.2
99.1
0
0.6
98.2
98.5
0
0.4
97.8
98.1
0
1.0
96.5
83.8
0.3
1.5
57.1
9.9
0.5
83.0
66.7
0
1.3
64.6
22.0
0
9.6
6.4
a
20Cu/SiO2
73.4
0
0
13.7
55.3
Conversion and selectivity were averaged between 0-8 h of TOS. Reaction conditions: H2 flow
-1
rate, 30 cm3 min-1; reaction temperature, 250 oC; WHSV, 6.60 h . The catalyst was reduced in H2
flow at 300 oC except 400oCfor 20Ni/SiO2 for 1 hprior to the reaction.
GVL, γ-valerolactone; MEK, methyl ethyl ketone; ALs, angelicalactones. Others included
pentanoic acid, pentenoic acid, and -butyrolactone.
a The reactionwas performed at a WHSV of3.30 h-1.

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Table 2 Vapor-phasehydrogentionof LA to GVL over various catalysts.
Temp. H2 pressure WHSV TOS GVLselect. GVLyield
Catalyst
Productivity
kgGVL kgcat.-1h-1
0.46
Ref.
(oC)
265
265
265
265
250
250
270
285
250
250
(bar)
1
(h-1)
0.512
0.512
0.513
0.169
1.13
(h)
50
50
100
-
(%)
90
(%)
90
Pd/C
10
Ru/C
1
98.6
99.9
87
98.6
99.9
85
0.50
10
Cu/SiO2
Cu/Al2O3
Ni/ZSM-5
Ni/SiO2
Ni/TiO2
Cu-Ni/SiO2
10
1
0.51
11
0.14
12
13
1
-
92.2
87
92.2
87
0.91
1
1.13
-
0.87
14
1
3.25 a
0.512
1.65
-
99.1
96
99.1
95.0
99.4
98.2
0.58
15
1 c
100
50
8
0.49
16
b
6Cu-14Ni/SiO2
6Cu-14Ni/SiO2
1
100
99.2
1.64
This study
This study
1
6.60
6.48
aGHSV, cm3 gcat-1 s-1;
b Cu:Ni:SiO2=60:20:20 weight ratio;
c Formic acid and nitrogen were used instead of hydrogen.

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20Ni/SiO2
6Cu-14Ni/SiO2
8Cu-12Ni/SiO2
14Cu-6Ni/SiO2
20Cu/SiO2
0
200 400 600 800
Temperature /°C
Fig. 1 TPR profiles of the 20Ni/SiO2, 20Cu/SiO2 and Ni-Cu/SiO2 withdifferent Ni and Cu
loadings.
◆
◆ Cu
▼ Ni
◆
20Cu/SiO2
▼
◆
▼
◆
6Cu-14Ni/SiO2
▼
▼
20Ni/SiO2
10 20 30 40 50 60 70
2degree
Fig. 2 XRD patterns of 20Cu/SiO2, 6Cu-14Ni/SiO2 and 20Ni/SiO2 after reduction. The reduction
temperature of 20Cu/SiO2, 6Cu-14Ni/SiO2,and 20Ni/SiO2 was 300, 300,400oC, respectively.

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Fig. 3 Change in the conversion in the reactions over different catalysts with time on stream.
Open square, 20Ni/SiO2; closed square, 4Cu-16Ni/SiO2; open circle, 6Cu-14Ni/SiO2; closed
circle, 14Cu-6Ni/SiO2; opentriangle, 16Cu-4Ni/SiO2,closed triangle, 20Cu/SiO2.
Reaction conditions: H2 flow rate, 30 cm3 min-1; reactiontemperature, 250 oC; WHSV,6.60 h-1.
100
98
96
94
Conversion
GVL selectivity
92
90
0
10 20 30 40 50
Time on stream /h
Fig. 4 Change in the conversion and selectivity in a long-run reaction over 6Cu-14Ni/SiO2.
Reaction conditions: H2 flow rate, 30 cm3 min-1; reactiontemperature, 250 oC; WHSV,1.65 h-1.

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Graphical abstract

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Highlights
1. Hydrogenation of levulinic acid to γ-valerolactone wasperformed over Cu-Nibimetallic catalyst.
2. SiO2-supported Cu-Nibimetallic catalysts showsstable catalytic activity in H2 flowat250 oC.
3. An excellentγ-valerolactone yield higherthan 98% wasobtained at Cu/Niweight ratio of 6/14.
4. A high γ-valerolactone productivity of 1.64kg kgcat.-1 h-1 wasobtained at a high WHSVof 1.65 h-1.
5. Inhibition of carbondeposition by Niand high selectivity of Cu improved the catalyst performance.