Hydrogenation of 3-hydroxypropanal into 1,3-propanediol over bimetallic Ru-Ni catalyst

Article abstract of DOI:10.1039/c7ra01184a

A series of Ni-based catalysts, including Ru/SiO₂, Ni/SiO₂ and Ru-Ni/SiO₂, were prepared and employed in the hydrogenation of 3-hydroxypropanal (3-HPA) to 1,3-propanediol (1,3-PDO). The catalysts were systematically characterized by means of XRD, TEM, HRTEM, SEAD, XPS, H₂-TPD, H₂-TPR and N₂-physisorption. It was indicated that the introduction of Ru onto the Ni/SiO₂ not only increased the porosity of catalyst and the degree of dispersion of Ni species but also promoted the reduction of Ni²⁺ to Ni⁰ and the generation of active hydrogen species. The catalytic performance evaluation showed that the Ru-40Ni/SiO₂ catalyst, among all others, could provide the largest yield of 1,3-PDO (above 99.0%) and highest TOF (4.70 × 10³ S^-1). The optimized reaction conditions over the Ru-40Ni/SiO₂ catalyst had been established as follows: reaction temperature = 80 °C, H₂ pressure = 2.0 MPa and LHSV = 0.4 h^-1. In consideration of its extremely low H₂ pressure and very high yield of 1,3-PDO for the hydrogenation of 3-HPA, to the best of our knowledge, the Ru-40Ni/SiO₂ catalyst appeared to be the most efficient catalyst among all others reported in the literature. The good performance enabled the Ru-40Ni/SiO₂ catalyst to be very promising in its industrial application.

Full text of DOI:10.1039/c7ra01184a

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Hydrogenation of 3-hydroxypropanal into 1,3-
propanediol over bimetallic Ru–Ni catalyst†
Cite this: RSC Adv., 2017, 7, 32027
ab
Li-Jun Li,‡a Wen-Jun Yi,‡a Tian-Wei Liu,a Chen Huanga and Zi-Sheng Chao
*
A series of Ni-based catalysts, including Ru/SiO2, Ni/SiO2 and Ru–Ni/SiO2, were prepared and employed in
the hydrogenation of 3-hydroxypropanal (3-HPA) to 1,3-propanediol (1,3-PDO). The catalysts were
systematically characterized by means of XRD, TEM, HRTEM, SEAD, XPS, H2-TPD, H2-TPR and N2-
physisorption. It was indicated that the introduction of Ru onto the Ni/SiO2 not only increased the
porosity of catalyst and the degree of dispersion of Ni species but also promoted the reduction of Ni2+
to Ni0 and the generation of active hydrogen species. The catalytic performance evaluation showed that
the Ru–40Ni/SiO2 catalyst, among all others, could provide the largest yield of 1,3-PDO (above 99.0%)
and highest TOF (4.70 ꢀ 103
S
ꢁ1). The optimized reaction conditions over the Ru–40Ni/SiO2 catalyst had
been established as follows: reaction temperature ¼ 80 ꢂC, H2 pressure ¼ 2.0 MPa and LHSV ¼ 0.4 hꢁ1
.
Received 26th January 2017
Accepted 13th April 2017
In consideration of its extremely low H2 pressure and very high yield of 1,3-PDO for the hydrogenation
of 3-HPA, to the best of our knowledge, the Ru–40Ni/SiO2 catalyst appeared to be the most efficient
catalyst among all others reported in the literature. The good performance enabled the Ru–40Ni/SiO2
catalyst to be very promising in its industrial application.
DOI: 10.1039/c7ra01184a
rsc.li/rsc-advances
contrast, the hydrogenation of 3-HPA could be conducted under
relatively warm reaction conditions and provides a very high
1. Introduction
yield of 1,3-PDO, and in fact, it is currently the predominant
method for the industrial production of 1,3-PDO.
1,3-Propanediol (1,3-PDO) is an important organic intermediate
in chemical industries and has found versatile applications in
the elds such as resins, adhesives, solvents, cosmetics, deter-
gents, biocides, and feedstuffs.1 Most importantly, 1,3-PDO is
the key raw material for the manufacture of polytrimethylene
terephthalate (PTT).2,3 Two routes have been reported in the
literature for the production of 1,3-PDO, biological and chem-
ical ones. The rst route involved the bioconversion of renew-
able resources (glucose, glycerol, etc.) to 1,3-PDO.3,4 This route,
however, was associated with a few drawbacks, e.g., long reac-
tion time, low 1,3-PDO yield,5 complicated purication of 1,3-
PDO from fermentation broth and large discharge of waste
water,6 largely restraining its development in industry. The
second route involved either the hydrogenolysis of glycerol or
the hydrogenation of 3-hydroxypropanal (3-HPA) to 1,3-PDO.
The hydrogenolysis of glycerol always operated under harsh
reaction conditions and provided a very low yield of 1,3-PDO,7,8
and accordingly, it is still far from industrial application. This
method has not been applied in industry up till now. In
There have been a few reports in the literature on catalysts
for the hydrogenation of 3-HPA,9–13 and these could be classied
mainly into three groups. The rst group comprised noble
metal catalysts. For example, 2% Pt/TiO2 and 5% Ru/SiO2
catalysts provided, respectively, a 98.7% yield of 1,3-PDO at
15.0 MPa (ref. 9) and an 89.0% yield of 1,3-PDO at 4.0 MPa.10
The main issues associated with these catalysts were the high
operation pressure and/or the relatively large usage of noble
metals. The second group included RANEY® Ni and nickel alloy
catalysts.11,12 Although a yield as high as 99.5% of 1,3-PDO could
be achieved over these catalysts, the hard separation of the
catalyst ne powder and reaction products and thus the diffi-
culty in the recycling use of the catalyst and low purity of
product still remained. The third group comprised supported
transition metal oxide catalysts, in particular, nickel oxide. For
instance, a yield of ca. 81.0% over an Ni/SiO2–Al2O3 catalyst was
obtained at 15.0 MPa.13 Compared to the rst and second
groups of catalysts, the third group usually provided a relatively
low yield of 1,3-PDO. There is no doubt that the development of
a low-cost and highly effective catalyst is currently highly
desired.
aCollege of Chemistry and Chemical Engineering, Hunan University, Changsha,
410082, China. E-mail: zschao@yahoo.com; chao_zs@aliyun.com; Fax: +86-731-
88713257; Tel: +86-731-88713257
As is well known, bimetallic catalysts,14,15 particularly those
consisting of noble and transition metals, may sometimes give
a superior activity, selectivity and deactivation resistance, rela-
tive to the corresponding monometallic catalysts. For instance,
bCollege of Materials Science and Engineering, Changsha University of Science &
Technology, Changsha, Hunan 410114, China
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c7ra01184a
‡ These authors contributed equally to this work.
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Ru–Ni catalysts have been widely employed in reactions such as
Before being employed for the hydrogenation of 3-HPA to
the methanation of CO16–19 and CO2,20,21 the hydrogenolysis of n- 1,3-PDO, all the catalysts were pressed into small discs and then
butane22 and the hydrogenation of D-glucose to sorbitol,23 crushed and sieved to 20–40 mesh.
exhibiting a much better catalytic performance than both the
Ru and Ni catalysts.
These were proved to benet from the optimization of the atmosphere by increasing the temperature to 550 C at 10 C
pore structure and the promotion of both the dispersion and minꢁ1 and holding that temperature for 4 h. Aer that, the
reducibility of active metal species by the addition of noble catalyst was cooled to room temperature under a hydrogen
metals to a Ni-based catalyst.16–18,20,21,23–26 To the best of our atmosphere.
Reduced catalysts were prepared using the following proce-
dure: the catalysts were reduced in an ambient hydrogen
ꢂ
ꢂ
knowledge, bimetallic Ru–Ni catalysts have never been tested in
the hydrogenation of 3-HPA.
2.3. Catalyst characterization
In this study, a series of Ru/SiO2, Ni/SiO2 and Ru–Ni/SiO2
catalysts were employed, for the rst time, for the hydrogena-
tion of 3-HPA to 1,3-PDO. The catalysts were characterized using
a series of techniques and their performances were evaluated
under various conditions. In addition, the structure–activity
relationship is discussed for a better insight into the catalyst.
X-ray diffraction spectroscopy (XRD) was performed with
a Bruker D8 Advance X-ray diffractometer under the following
˚
conditions: Cu target Ka radiation (l ¼ 1.54187 A); scanning
voltage 40 kV; scanning current 40 mA; scanning speed 6ꢂ
minꢁ1; scanning step 0.02ꢂ. The crystal size of the Ni particles
was calculated using the Scherrer equation with the peak at 2q ¼
44.4ꢂ.27
Transmission electron microscopy (TEM), high resolution
transmission electron microscopy (HRTEM) and selected area
electron diffraction (SAED) were performed with a JEM-2100F
transmission electron microscope operated at an acceleration
voltage of 200 kV. Before determination, the specimen was
dispersed into ethanol using ultrasonic treatment and then the
resultant suspension was dropped onto a carbon-coated copper
grid.
2. Experimental
2.1. Chemicals
Ruthenium chloride hydrate (RuCl3$xH2O, Ru > 37 wt%), nickel
nitrate hexahydrate (Ni(NO3)2$6H2O) and colloidal silica solu-
tion (commercial grade, SiO2$nH2O, 30.0 wt%, Na2O type, pH z
10) were purchased from Sinopharm Chemical Reagent limited
corporation. All chemicals were used without further
purication.
H2 temperature programmed desorption (H2-TPD) was per-
formed using a Quantachrome Autosorb-1 instrument equip-
ped with a thermal conductivity detector (TCD). The catalyst
specimen (500 mg) was placed in a quartz reactor and reduced
by increasing the temperature from room temperature to 550 ꢂC
at 10 ꢂC minꢁ1 and holding that temperature for 4 h in a stream
of 10% H2/Ar with a ow rate of 40 mL minꢁ1. Then, the catalyst
was cooled to 40 ꢂC and exposed to a stream of 10% H2/Ar with
a ow rate of 40 mL minꢁ1 till the saturation adsorption of H2
was reached. Aer that, the catalyst was purged with N2 at room
temperature for 30 min to remove the physically adsorbed H2.
The desorption of H2 was carried out in a stream of N2 with
a owꢂrate of 30 mL minꢁ1 from 40 ꢂC to 600 ꢂC at a heating rate
of 10 C minꢁ1. The amount of desorbed hydrogen was deter-
mined using TCD. The calibration of hydrogen uptake was done
by injecting a certain volume of pure hydrogen into the inlet
stream of the reducing gas. On the basis of the peak area of the
H2-TPD prole and the standard calibration process, the
hydrogen uptake was estimated, assuming that one H atom was
adsorbed per metal atom.28 This enabled the degree of disper-
sion to be calculated, according to eqn (1):26
2.2. Catalyst preparation
Monometallic catalysts were prepared using a procedure
described as follows: calculated amounts of RuCl3$xH2O and
colloidal silica solution were mixed at room temperature with
strong stirring for 8 h. The resultant mixture was dried over-
night at 120 ꢂC and then calcined in ambiꢁe1nt air by increasing
the temperature to 550 ꢂC at 10 ꢂC min and holding that
temperature for 4 h. This generated the Ru/SiO2 catalyst, in
which the molar percentage of ruthenium was 1%. A series of
Ni-based catalysts were also prepared using the same procedure
as above, except that RuCl3$xH2O was replaced with Ni(NO3)2-
$6H2O. The obtained Ni-catalysts are denoted as yNi/SiO2 (y ¼
20 or 40), where y refers to the molar percentage of nickel.
The bimetallic catalyst was prepared using the procedure
described as follows: calculated amounts of RuCl3$xH2O,
Ni(NO3)2$6H2O and colloidal silica solution were mixed at room
temperature with strong stirring for 8 h. Then the resultant
mixture was dried overnight at 120 ꢂC and calcined in ambient
air by increasing the temperature to 550 ꢂC at 10 ꢂC minꢁ1 and
holding that temperature for 4 h. This generated the Ru–40Ni/
SiO2 catalyst, in which the molar percentages of ruthenium and
nickel were 1% and 40%, respectively.
D% ¼ 1.17X/wf
(1)
where X ¼ the H2 uptake in mmol per g of catalyst, w ¼ the
For the purpose of comparison, an unsupported SiO2 catalyst weight percentage of nickel, and f ¼ the fraction of nickel
was prepared using the following procedure: a certain amount reduced to the metal.
of colloidal silica solution (30.0 wt%) was dried overnight at
The average crystallite diameter, d, was calculated from the
120 ꢂC and then calcined in ambient air by increasing the degree of dispersion, assuming that the crystals were all
temperature to 550 ꢂC at 10 ꢂC minꢁ1 and holding that spherical and possessed the same dimensions,26 as shown by
temperature for 4 h. The obtained catalyst is denoted as SiO2.
eqn (2):
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n03ꢁHPA ꢁ n13ꢁHPA
d (nm) ¼ 97.1/(D%)
(2)
X3ꢁHPA ðmol%Þ ¼
S1;3ꢁPDO ðmol%Þ ¼
ꢀ 100
ꢀ 100
(3)
(4)
n03ꢁHPA
N2 physisorption was carried out with a Quantachrome
Autosorb-1 automated physisorption and chemisorption
analyzer at liquid N2 temperature. Before the measurements,
the catalyst was degassed at 150 ꢂC for 2 h under a vacuum of 4
ꢀ 10ꢁ4 Pa. The BET method was employed to calculate the
specic surface area, with a correlation coefficient above 0.9999.
The total pore volume was recorded at P/Po ¼ 0.99. The pore size
distribution was determined using the standard Barrett–Joyner–
Halenda (BJH) method.
n1;3ꢁPDO
n03ꢁHPA ꢁ n13ꢁHPA
Y1,3-PDO (mol%) ¼ X3-HPA ꢀ S1,3-PDO/100
(5)
(6)
À
Á
Y1;3ꢁPDO ꢀ F3ꢁHPA
TOF sꢁ1
¼
W ꢀ D
where n03-HPA and n13-HPA denote the molar content of 3-HPA in
the reactant and product, respectively; n1,3-PDO refers to the
molar content of 1,3-PDO in the product; W, F3-HPA and D are the
weight of the catalyst, molar ow rate of 3-HPA, and the
dispersion of the active site, respectively.
H2 temperature programmed reduction (H2-TPR) was con-
ducted using a Quantachrome Autosorb-1 instrument equipped
with a thermal conductivity detector (TCD). The catalyst spec-
imen (50 mg) was placed in a quartz reactor, pretreated in a ow
of N2 (40 mL minꢁ1) at 400 ꢂC for 30 min and then cooled down
to 50 C in a ow of N2 (40 mL minꢁ1). Aer that, the catalyst
ꢂ
3. Results and discussion
was exposed to a ow of 10% H2/Ar with a ow rate of 40 mL
minꢁ1 while the temperꢁat1ure was raised from 100 ꢂC to 700 ꢂC
at a rate of 10 ꢂC min and the signal was simultaneously
recorded using TCD.
X-ray photoelectron spectroscopy (XPS) was performed using
a K-Alpha XPS system with a monochromatic Al Ka X-ray source
and a charge neutralizer. The binding energies (B.E.) of O 1s, Ru
3d and Ni 2p3/2 core-levels were recorded. The B.E. were referenced
to the C 1s peak at 284.8 eV for surface adventitious carbon. In
order to determine the nature and chemical state of the specic
species present in the specimen, the peak was deconvolved and
tted using a non-linear least squares tting program with a mix
of Gaussian and Lorentzian shapes and a Shirley baseline.29–34
3.1. Characterization
The XRD patterns of the reduced and used catalysts are shown
in Fig. 1. The broad diffraction peak at 2q ¼ 22ꢂ present in
Fig. 1a indicates that the SiO2 in all the catalysts possesses the
typical amorphous character.16 The weak diffraction peak at 2q
¼ 44.0ꢂ over both the reduced (Fig. 1b) and used (Fig. 1f) Ru/
SiO2 catalysts is attributed to metallic Ru.38 This peak of
metallic Ru is, however, hard to be observed over the reduced
and used Ru–40Ni/SiO2 catalysts (Fig. 1e and i). This may be due
to the fact that the Ru species has been incorporated into the
silica network39 or the Ru crystals have very small dimensions
(<4 nm) and thus are unable to be detected using XRD.22,24,40 The
above result also indicates that no change occurred for Ru aer
the reduced catalyst was used in the reaction. The diffraction
peaks at 2q ¼ 44.3ꢂ, 51.6ꢂ and 76.3ꢂ are present over the 20Ni/
SiO2, 40Ni/SiO2 and Ru–40Ni/SiO2 (Fig. 1c–e and g–i) catalysts,
and they are attributed to metallic Ni (JCPDS no. 04-0850). The
intensity of these three peaks increases obviously with
increasing content of Ni in the catalyst and decreased largely
over the used catalysts relative to the corresponding reduced
2.4. Hydrogenation of 3-HPA to 1,3-PDO
The reaction was performed in a xed-bed ow-type stainless
reactor, which was mounted in a tubular electric heater. The
catalyst (1.0 g) was loaded in the middle of the reactor, and the
upper space of the catalyst bed in the reactor was lled with inert
quartz granulates (10–20 mesh). The catalyst was rst in situ
activated by reducing in a hydrogen atmosphere at 550 ꢂC for 4 h,
and then it was cooled to a preset temperature in the range of 40–
ꢂ
150 C. Then, a ow of H2 at a certain pressure in the range of
1.0–7.0 MPa and a stream of reactant, i.e., 10 wt% aqueous
solution of 3-HPA, were simultaneously introduced into the
reactor. The ow rates of the reactant and H2 were regulated so
that the liquid hourly space velocity (LHSV) had a certain value in
the range of 0.2–0.8 hꢁ1. The reaction was thus conducted under
the above conditions. The effluent from the bottom of the reactor
was passed through a gas–liquid separator cooled with ice water.
The liquid products were collected for analysis.
Qualitative and quantitative analysis of the liquid products
mixture was carried out with a Varian Saturn 2200/CP 3800 GC/
MS instrument equipped with a ame ionization detector (FID)
and two CP-Wax 52CB fused silica capillary columns (15 m ꢀ
0.32 mm).
The conversion of 3-HPA (X3-HPA), selectivity to 1,3-PDO
(S1,3-PDO), yield of 1,3-PDO (Y1,3-PDO) and turnover frequency
(TOF)35–37 were, respectively, calculated using eqn (3)–(6):
Fig. 1 XRD patterns of reduced (left) and used (right) catalysts. (a) SiO2,
(b) Ru/SiO2, (c) 20Ni/SiO2, (d) 40Ni/SiO2, (e) Ru–40Ni/SiO2, (f) Ru/SiO2,
(g) 20Ni/SiO2 (h) 40Ni/SiO2, (i) Ru–40Ni/SiO2. (f–h) were all used for
4 h and (i) for 132 h, respectively.
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47-1049). Furthermore, these peaks for cubic NiO are absent for
the used Ru–40Ni/SiO2 catalyst. This result indicates that,
during the reaction, a proportion of metallic Ni species have
been transformed into NiO species over the catalysts containing
no Ru, but the above transformation of Ni species can be
inhibited due to the loading of Ru onto the catalyst. The reason
for the above transformation of the Ni species is most probably
due to the fact that there is interaction between the Ni species
and SiO2 network, forming the Si–O–Ni species. During the
reaction, the Si–O–Ni species can be hydrolyzed into Si–OH and
Ni(OH)x by the water in 3-HPA solution, and the dehydrogena-
tion of Ni(OH)x leads to the formation of NiO species. However,
the presence of Ru can easily initiate the generation of active H
species at a relatively low temperature, and this kind of active H
species is transferred onto the NiO species via a hydrogen spill-
over process, and thus enables the NiO species to be reduced to
metallic Ni species during the hydrogenation of 3-HPA to 1,3-
PDO. In this sense, the presence of Ru stabilizes the metallic Ni
species, avoiding the transformation of metallic Ni into NiO.
Fig. 2 shows the TEM micrographs and particle size distri-
butions for various reduced catalysts. One can see that the
particles of the 40Ni/SiO2 catalyst are aggregated to a larger
extent and possess a broader size distribution as well as a larger
average size, relative to those of the 20Ni/SiO2 catalyst (cf.
Fig. 2a–d). Compared to the 40Ni/SiO2 catalyst, both the extent
of aggregation and average size of the particles becomes smaller
and the particle size distribution narrower for the Ru–40Ni/SiO2
catalyst (cf. Fig. 2c–f). The above result is due to the fact that the
increase in the Ni content leads to the generation of larger Ni
particles over the SiO2 support; however, the sintering of Ni
particles is inhibited, to some extent, by the presence of Ru.16
Fig. 3 shows the HRTEM micrograph and SAED pattern for
the reduced Ru–40Ni/SiO2 catalyst. One can see that the
micrograph (Fig. 3a) comprises mainly the lattice fringes with
d ¼ 0.21 nm and a small amount of lattice fringes with d ¼
0.20 nm, which can be attributed to the Ru (101) crystalline
plane (JCPDS 06-0663) and Ni (111) crystalline planes (JCPDS 04-
0850), respectively. In a few areas, the lattice fringes for the Ru
(101) and Ni (111) are overlapped, indicating that the Ru
Fig. 2 TEM micrographs (left) and particle size distributions (right) for
the various reduced catalysts. (a, b) 20Ni/SiO2; (c, d) 40Ni/SiO2; (e, f)
Ru–40Ni/SiO2.
ones (cf. Fig. 1c–e and g–i). The weak diffraction peaks at 2q ¼
37.3ꢂ, 43.3ꢂ and 62.9ꢂ are present for the used 20Ni/SiO2 and
40Ni/SiO2 catalysts (Fig. 1g and h), with their intensity
increasing with the increase in Ni content of the catalyst, but
they are absent over the corresponding reduced ones (Fig. 1c
and d). These three peaks are attributed to cubic NiO (JCPDS no.
Fig. 3 HRTEM micrograph (a) and SAED pattern (b) for the reduced Ru–40Ni/SiO2 catalyst.
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Table 1 Degree of dispersion and average particle size of Ni over the Table 2 Textural properties for the reduced and used catalysts
various reduced catalysts
SBETa (m2 gꢁ1
)
Vtotal (cm3 gꢁ1
)
DMP (nm)
b
c
Catalyst
d (nm)
SiO2
Ru/SiO2
136.2
154.8
98.6
0.24
0.39
0.38
0.39
0.44
0.33
0.32
0.32
0.39
2.5
10.1
13.2
13.3
15.1
9.4
11.2
13.4
23.2
Catalyst
Da (%)
H2-TPDb
XRDc
20Ni/SiO2
40Ni/SiO2
Ru–40Ni/SiO2
Used Ru/SiO2
Used 20Ni/SiO2
Used 40Ni/SiO2
20Ni/SiO2
40Ni/SiO2
Ru–40Ni/SiO2
11.79
7.67
7.89
8.24
12.67
12.31
25.4
27.3
22.0
93.2
107.2
136.5
113.1
98.9
d
d
d
a
b
Degree of dispersion determined using H2-TPD. Average size
c
determined using H2-TPD. Crystal size calculated using the Scherrer
e
equation using the peak at 2q ¼ 44.4ꢂ.
Used Ru–40Ni/SiO2
66.4
a
b
c
SBET, specic surface area. Vtotal total pore volume. DMP, most
d
e
frequent pore size. The catalyst was used for 4 h. The catalyst was
used for 132 h.
particles are in close contact with the Ni particles. The SAED
pattern (Fig. 3b) provides additional evidence for the presence
of cubic Ni and cubic Ru in the catalyst.
Ni and the further loading of Ru. This is due to the fact that
small amounts of Ni and/or Ru have been incorporated into the
silica network and thus hindered the sintering of catalyst
particles.39 Compared to the reduced catalysts, the used cata-
lysts have only a very small change in the DMP, except for the
used Ru–40Ni/SiO2 catalyst, which possesses an obviously larger
DMP than the corresponding reduced one.
Table 2 lists the textural properties of the reduced and used
catalysts. One can see that the reduced Ru/SiO2 and Ru–40Ni/
SiO2 possess a larger specic surface area (SBET), total pore
volume (Vtotal) and most frequent pore size (DMP) than the cor-
responding reduced SiO2 and 40Ni/SiO2, respectively. This shows
that the loading of Ru increases the porosity of the catalyst. This
is due to the fact that Ru can be incorporated into the silica
network prepared via a sol–gel process,39 and thus a proportion of
the Si–O–Si structure is replaced with a Si–O–Ru–O–Si structure,
which not only hinders the sintering of catalyst particles45 but
also enables the catalyst particles to be assembled into the
Table 1 shows the degree of dispersion (D) and average
particle size (d) of Ni over various reduced catalysts. For the yNi/
SiO2 (y ¼ 20 or 40) catalyst, the degree of dispersion of Ni
decreases and the average particle size of Ni increases with
increasing Ni content in the catalyst. In comparison with the
40Ni/SiO2 catalyst, the degree of dispersion of Ni becomes larger
and the average particle size of Ni smaller over the Ru–Ni/SiO2
catalyst. This indicates that the presence of Ru leads to an
increase in the degree of dispersion of Ni and the decrease in
the formation of larger Ni particles.23 This result is consistent
with that derived from the TEM determination.
Fig. 4 shows the N2 adsorption–desorption isotherms and
pore size distribution proles for the reduced and used cata-
lysts. One can see that the isotherms for all the catalysts belong
to the type IV and possess an H2 hysteresis, according to the
IUPAC classication,41 indicating the presence of mesopores in
the catalysts.42–44 The pore size distributions for all the catalysts
are unimodal and relatively narrow in the range of 2.5–30 nm,
indicating a relatively high monodispersity of mesopores.42,43
The most frequent pore size (DMP) increases with the loading of
mesoporous structure with a higher SBET and Vtotal and DMP
.
Compared to the reduced SiO2, the SBET is decreased and both
the Vtotal and DMP are increased with the loading of Ni onto the
silica (the reduced 20Ni/SiO2 and 40Ni/SiO2 catalysts), particu-
larly for the higher loading of Ni. This is due to the fact that the
deposition and aggregation of Ni particles increases the size of
the catalyst particles and thus decreases the SBET of Ni–SiO2
catalyst;46 furthermore, the presence of Ni particles also roughens
the surface of the silica particles, and the assembly leads to the
formation of a mesoporous structure with a larger Vtotal and DMP
.
Compared to the reduced yNi/SiO2 catalysts (y ¼ 20 or 40), the
used ones possess a larger SBET but a smaller porosity (Vtotal and
DMP). This is due to the fact that, as has been pointed out in the
XRD characterization, a proportion of Ni species can be hydro-
lyzed into Ni(OH)x, which is partially soluble in water. This may
decrease, to some extent, the aggregation of Ni particles and thus
increase the SBET of catalyst. In addition, the dissolved Ni(OH)x
may be re-deposited into the pores of catalyst, decreasing the
pore volume and average pore size. Compared to the reduced Ru/
SiO2 catalyst, the SBET, Vtotal and DMP all decreased over the used
Ru/SiO2 catalyst. Similarly, the used Ru–40Ni/SiO2 catalyst
possesses a smaller SBET and Vtotal relative to the reduced Ru–
Fig. 4 N2 adsorption–desorption isotherms (A) and pore size distri-
butions (B) for the reduced and used catalysts. (a) SiO2, (b) Ru/SiO2, (c)
20Ni/SiO2, (d) 40Ni/SiO2, (e) Ru–40Ni/SiO2, (f) used Ru/SiO2, (g) used
20Ni/SiO2 (h) used 40Ni/SiO2, (i) used Ru–40Ni/SiO2. (f–h) were all
used for 4 h and (i) for 132 h.
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40Ni/SiO2 catalyst. This is due to the fact that the Si–O–Ru–O–Si XRD, H2-TPD and TEM, the 40Ni/SiO2 catalyst possesses a larger
structure is partially destroyed via the reduction of the Ru species average size of Ni particles than the 20Ni/SiO2 catalyst. Therefore,
during the hydrogenation reaction, and this causes, to some the increase in the average size of the Ni particles accounts for the
extent, sintering of the catalyst particles. However, it was also above variations in both the reduction temperature and compo-
found that the used Ru–40Ni/SiO2 catalyst possesses an abnor- sition of the Ni species for the 40Ni/SiO2 catalyst relative to the
mally larger DMP than the reduced Ru–40Ni/SiO2 catalyst, the 20Ni/SiO2 catalyst. Over the Ru–40Ni/SiO2 catalyst, the reduction
reason for which is still unclear. One possibility may be related to peaks appear at 177.0 ꢂC, 299.0 ꢂC and 355.5 ꢂC, which can,
the obviously long TOS of the used Ru–40Ni/SiO2 catalyst (132 h), respectively, be attributed to the highly dispersed RuO2 species
relative to the used 40Ni/SiO2 catalyst (4 h). The deposition of (HD-RuO2),52 the S-NiO, and the W-NiO–SiO2. It has been iden-
byproducts with high molecular weights on the surface and also tied (see Table 1 and Fig. 1) that the Ru–40Ni/SiO2 catalyst
in the pores of the Ru–40Ni/SiO2 catalyst leads not only to the possesses a smaller average size of Ni particles than the 40Ni/SiO2
irregular aggregation of catalyst particles, generating large voids catalyst. Therefore, both the peaks for the L-NiO and S-NiO–SiO2
among the catalyst particles, but also to occupation of the pores disappear, and also the reduction temperatures for the S-NiO and
of the catalyst, decreasing SBET and Vtotal
.
W-NiO–SiO2 should be higher over the Ru–40Ni/SiO2 catalyst
Fig. 5 shows the H2-TPR proles for the various unreduced relative to the 40Ni/SiO2 catalyst. However, the reduction
catalysts. The broad peaks in the proles have been deconvolved temperature for the S-NiO and W-NiO–SiO2 over the Ru–40Ni/
and tted to the component peaks, and the temperatures at the SiO2 catalyst are, in fact, abnormally lower than over the 40Ni/
maxima and the area percentages of the peaks, corresponding to SiO2 catalyst, and this is due to the presence of Ru species, which
the reduction temperatures and percentage contents of Ni causes the inter-particle hydrogen spillover from Ru particles to
species, are summarized in Table S1 (ESI†). One can see from Ni particles.16,18,20,23,25 As for the hydrogen spillover, Ru species are
Fig. 5 that all the catalysts show three reduction peaks. Over the rst reduced to Ru0 by H2, while H2 molecules are dissociated on
20Ni/SiO2 catalyst, the reduction peaks appear at 382.8 ꢂC, the surface of Ru0 to form the active hydrogen species; then, the
450.3 ꢂC and 585.7 ꢂC, which can, respectively, be ascribed to the active hydrogen species can be transferred to the neighboring Ni
small NiO particles (S-NiO),47 the NiO particles weakly interacting species in close proximity due to the contact between the Ru0 and
with SiO2 (W-NiO–SiO2),48 and the NiO particles strongly inter- NiO particles and/or the contact of SiO2 with both the Ru0 and
acting with SiO2 (S-NiO–SiO2).49 Over the 40Ni/SiO2 catalyst, the NiO particles, and this enables the Ni species to be easily reduced
reduction peaks appear at 306.0 ꢂC, 381.0 ꢂC and 453.5 ꢂC, which to Ni0 at an obviously lower temperature, relative to the normal
can, respectively, be assigned to the large NiO particles (L-NiO),50 reduction of NiO by H2 without hydrogen spillover.25 The pres-
the S-NiO, and the W-NiO–SiO2. Pawelec et al.51 reported that ence of Ru0 and Ni0 and their contact with each other was evi-
larger NiO particles possessed a smaller interface with the SiO2 denced in the above HRTEM characterization. In Table S1,† one
surface and thus resulted in a weaker interaction between NiO can nd that the percentage content of isolated NiO (L-NiO + S-
particles and SiO2 support, enabling the nickel species to be more NiO) over various catalysts has the order 40Ni/SiO2 > Ru–40Ni/
easily reduced. As found from the above characterizations using SiO2 > 20Ni/SiO2 and that of the Ni species interacting with SiO2
(W-NiO–SiO2 + S-NiO–SiO2) shows the reverse order, i.e., 40Ni/
SiO2 < Ru–40Ni/SiO2 < 20Ni/SiO2. This implies that the 40Ni/SiO2
catalyst possesses a lower degree of dispersion of Ni, relative to
the 20Ni/SiO2 catalyst,53 and in fact, this was evidenced from the
result listed in Table 1. The above result also indicates that the
presence of Ru favors a high dispersion of Ni over SiO2 support
via the interaction between the latter two.
Fig. 6 shows the Ni 2p3/2 XPS spectra for the various unreduced
catalysts, and the corresponding B.E. of the Ni species are
summarized in Table S2.† One can see that all the catalysts exhibit
a broad main peak with B.E. of ca. 855.0 eV and a shoulder peak
with B.E. of 860.4–860.9 eV. The main peak is deconvolved and
tted into two components situating at B.E. ¼ 854.1 ꢃ 0.2 eV and
855.9 ꢃ 0.2 eV, which can be attributed to Ni2+ species in bulk
NiO16 and that interacting with SiO2 (Ni2+–SiO2),16 respectively,
while the shoulder peak corresponds to the satellite of Ni 2p3/2
peak.29 It is found that, over all the catalyst, the Ni species consists
of mainly isolated NiO and a relatively small amount of Ni2+
attached to SiO2. With increasing Ni content or loading of Ru in
the catalyst, the content of NiO increases and that of Ni2+–SiO2
decreases. These results are consistent with those derived from the
H2-TPR characterization. Fig. S1† shows the O 1s and Ru 3d XPS
spectra for the various unreduced catalysts. One can see that the O
1s spectra for all the 20Ni/SiO2, 40Ni/SiO2 and Ru–40Ni/SiO2
Fig. 5 H2-TPR profiles for the various unreduced catalysts. (a) 20Ni/
SiO2, (b) 40Ni/SiO2, (c) Ru–40Ni/SiO2.
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Main reaction
Side reactions
3-HPA + H2 / 1,3-PDO
3-HPA 4 acrolein + H2O
(7)
(8)
(9)
3-HPA + H2O 4 3-HPA-hydrate
3-HPA 4 3-HPA-dimer
(10)
3-HPA + acrolein / 4-oxa-1,7-heptanedial
(11)
4-oxa-1,7-heptanedial 4 4-hydroxy-3-formyltetea-
hydropyran
(12)
(13)
4-oxa-1,7-heptanedial + H2 / 4-oxa-1,7-heptanediol
The conversion of 3-HPA (X3-HPA), selectivity to 1,3-PDO
(S1,3-PDO), yield of 1,3-PDO (Y1,3-PDO) and TOF over the various
catalysts for the hydrogenation of 3-HPA to 1,3-PDO are listed in
Table 3. One can see that the TOF over the Ru/SiO2 catalyst is
higher than over the 20Ni/SiO2 catalyst, indicating a larger
efficiency of the Ru species than the Ni species in catalyzing the
hydrogenation of 3-HPA to 1,3-PDO. However, due to the much
lower loading of Ru, relative to that of Ni, over SiO2, there is only
a limited amount of active sites available for the conversion of 3-
HPA over the Ru/SiO2 catalyst, and this leads to a lower
conversion of 3-HPA, selectivity to 1,3-PDO and yield of 1,3-PDO
over Ru/SiO2 catalyst than over the 20Ni/SiO2 catalyst.
Compared to the 20Ni/SiO2 catalyst, the conversion of 3-HPA
and TOF are lower but the selectivity to 1,3-PDO and yield of 1,3-
PDO are both larger over the 40Ni/SiO2 catalyst. This is due to
the fact that, on the one hand, the 20Ni/SiO2 catalyst possesses
a smaller average size of Ni particle, higher degree of dispersion
of Ni and larger specic surface area, as well as comparable pore
volume and average pore size (see Tables 1 and 2), relative to the
40Ni/SiO2 catalyst, enabling more 3-HPA to be adsorbed and
activated over the former catalyst than over the latter catalyst;
on the other hand, the 20Ni/SiO2 catalyst contains more Ni
species interacting with SiO2 (W-NiO–SiO2 + S-NiO–SiO2) than
the isolated NiO species (L-NiO + S-NiO), relative to the 20Ni/
SiO2 catalyst, leading to an increased difficulty for the reduction
of Ni species (higher reduction temperature), as shown in Table
S1,† and thus for the activation of H2. Therefore, there would be
a surplus of activated 3-HPA but a deciency of activated H2 over
the 20Ni/SiO2 catalyst, and this increases the extent of the side
reactions described in eqn (7)–(13) and thus decreases the
selectivity to 1,3-PDO relative to the 40Ni/SiO2 catalyst. Never-
theless, the higher degree of dispersion of Ni over the 20Ni/SiO2
catalyst than over the 40Ni/SiO2 catalyst means that there are
relatively more active Ni species available for the conversion of
3-HPA to 1,3-PDO, leading to a higher TOF over the former
catalyst than over the latter catalyst. Compared to the 40Ni/SiO2
catalyst, the Ru–40Ni/SiO2 catalyst exhibits a higher conversion
of 3-HPA, selectivity to 1,3-PDO, yield of 1,3-PDO and TOF. This
is due to the fact that, compared to the 40Ni/SiO2 catalyst, the
Fig. 6 Ni 2p3/2 XPS spectra for the various unreduced catalysts.
catalysts exhibit a main peak at B.E. ¼ 532.0–532.4 eV and
a shoulder at B.E. ¼ 529.5–529.8 eV, while the Ru/SiO2 catalyst
displays only a peak at 532.6 eV. The peak at B.E. ¼ 532.0–532.6 eV
can be ascribed to the lattice oxygen in SiO2 (ref. 32 and 33) and
that at 529.5–529.8 eV to the lattice oxygen in nickel oxide.34 The
Ru 3d spectrum for the Ru/SiO2 catalyst exhibits two weak peaks at
B.E. ¼ 281.2 and 285.2 eV, being attributed to Ru 3d5/2 and Ru
3d3/2, respectively, and a strong peak at 284.8 eV is related to the C
1s of surface carbonaceous contamination,30–32 while that for the
Ru–40Ni/SiO2 catalyst also displays the C 1s peak at 284.8 eV. The
failure to identify the Ru 3d peak over the Ru–40Ni/SiO2 catalyst
may be due to the fact that the Ru content is too low on the surface
of the catalyst to be detected using XPS. The possible reasons are
as follows: (i) the Ru content in the bulk sample is quite low; (ii)
the Ru species is incorporated into the silica network; and (iii) the
Ru species is coated with the Ni species.21
3.2. Structure–activity relationship in the hydrogenation of
3-HPA over various catalysts
Several possible reactions were supposed to happen during the
hydrogenation of 3-HPA as follows.54 Of these, reactions (8)–
(10), and (12) are reversible, while (7), (11) and (13) are
irreversible.
As the mechanism of the hydrogenation of 3-HPA has always
been thought to follow the Langmuir–Hinshelwood mecha-
nism,55 in which the reactants (3-HPA and H2) are absorbed and
then activated to form the target product (1,3-PDO), the ability
to adsorb and active the reactants is the most signicant
property for the catalyst. In particular, the activation of H2 is an
important process in the hydrogenation of 3-HPA.56
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Table 3 Results for the hydrogenation of 3-HPAa
active sites and increases the porosity of catalyst. This ensures
that a high conversion of 3-HPA at a high selectivity to 1,3-PDO
can be achieved over the Ru–Ni/SiO2 catalyst. Therefore,
a matching between the abilities of catalyst for the activation of
3-HPA and H2 is vital in the hydrogenation of 3-HPA to 1,3-PDO.
Based on the above discussions, a possible mechanism for the
hydrogenation of 3-HPA to 1,3-PDO over the Ru–Ni/SiO2 catalyst
has been proposed, as shown in Scheme 1.
X3-HPA
S1,3-PDO
Y1,3-PDO
TOF
Catalyst
(mol%)
(mol%)
(mol%)
(ꢀ103 Sꢁ1
)
Ru/SiO2
32.52
73.26
62.83
99.30
56.16
62.60
93.50
99.71
18.26
45.86
58.74
99.01
3.80
3.71
2.84
4.70
20Ni/SiO2
40Ni/SiO2
Ru–40Ni/SiO2
a
X3-HPA: conversion of 3-HPA. S1,3-PDO: selectivity to 1,3-PDO. Y1,3-PDO
:
yield of 1,3-PDO. Reaction conditions: T ¼ 80 ꢂC, P ¼ 2.0 MPa, LHSV
¼ 0.4 hꢁ1, time on stream (TOS) ¼ 2 h.
3.3. Optimization of the reaction conditions
Fig. 7 shows the effect of reaction conditions, including reaction
temperature, H2 pressure, LHSV of 3-HPA and time on stream
(TOS), on the hydrogenation of 3-HPA over the Ru–40Ni/SiO2
catalyst.
Ru–40Ni/SiO2 catalyst possesses a smaller average size and thus
a higher degree of dispersion of Ni particles (see Table 1) to
provide more exposed active sites, and also, a higher porosity
(specic surface area, pore volume and average pore size; see
Table 2) to provide more access and space for both the fast
diffusion of reactants (3-HPA and hydrogen species) and prod-
ucts; in addition, the presence of Ru enables the generation of
active hydrogen species via a hydrogen spillover process that
favors both the reduction of Ni species to active Ni0 at relatively
low temperatures (see Fig. 5) and the hydrogenation of 3-HPA to
1,3-PDO at a high conversion and selectivity. Among all the
others, the Ru–40Ni/SiO2 catalyst possesses the best perfor-
mance and the largest efficiency for the hydrogenation of 3-HPA
to 1,3-PDO, providing a 99.3% conversion of 3-HPA, 99.7%
selectivity to 1,3-PDO and 99.0% yield of 1,3-PDO at a TOF of
Fig. 7a shows the effect of reaction temperature. One can see
that, with increasing reaction temperature, the conversion of 3-
HPA increases approximately linearly. This is due to the fact
that the increase in the reaction temperature promotes the
mass transfer rate and also favors the activation of reactants.56
The selectivity to 1,3-PDO increased rst, achieving its
maximum at 80 ꢂC, and then decreased as the reaction
temperature increased. This result can be explained by the fact
that both the rates for the hydrogenation reaction and the
hydrogen mass transfer can be accelerated by increasing the
reaction temperature; however, the hydrogenation of 3-HPA to
1,3-PDO is an exothermic reaction, and accordingly, it is sup-
pressed at too high temperatures. Moreover, high temperatures
also promote the side reactions, leading to a decrease in the
selectivity to 1,3-PDO.56,57 Therefore, the optimal reaction
4.70 ꢀ 103 Sꢁ1
.
The above results indicate that, while a smaller average size
of Ni particles and thus a higher degree of dispersion of Ni
species over the Ni/SiO2 catalyst provides more active sites for
the activation of 3-HPA, it is, however, unfavorable for the
activation of H2. This leads to an insufficient amount of acti-
vated hydrogen relative to the amount of activated 3-HPA and
accordingly a relatively high conversion of 3-HPA but a low
selectivity to 1,3-PDO over the Ni/SiO2 catalyst. The introduction
of Ru onto the Ni/SiO2 catalyst not only promotes the ability for
the activation of H2 but also provides an additional number of
ꢂ
temperature is 80 C, taking into consideration both the high
conversion of 3-HPA and the high selectivity to 1,3-PDO.
Fig. 7b shows the effect of H2 pressure. It can be seen that, on
increasing the pressure from 2.0 MPa to 3.0 MPa, both the
conversion of 3-HPA and selectivity to 1,3-PDO increase; on
further increasing the pressure from 3.0 MPa to 7.0 MPa, the
conversion of 3-HPA increases only slightly and the selectivity to
1,3-PDO increases obviously. The yield of 1,3-PDO increases
from 77.4% to 100% with the pressure increasing from 2.0 MPa
to 7.0 MPa. This indicates that the increase in the H2 pressure
has a positive effect on the conversion of 3-HPA and the selec-
tivity to 1,3-PDO.58 This is due to the fact that, as is well known,
the gas–liquid–solid mass transfer resistance of hydrogen
constitutes a very important limiting factor for many hydroge-
nation reaction, and therefore, an increase in the H2 pressure
promotes the accessibility of H2 at the active sites of the catalyst,
favoring the hydrogenation conversion of 3-HPA to 1,3-PDO.59
In particular, it should be noted that a relatively high conver-
sion of 3-HPA (ca. 88.0%) at a high selectivity to 1,3-PDO (ca.
90.0%) has been achieved at appreciably low H2 pressures (2.0
MPa), and moreover, a nearly complete conversion of 3-HPA at
ca. 100% selectivity to 1,3-PDO can be achieved over the Ru–
40Ni/SiO2 catalyst. The relatively low H2 pressure employed in
this work is of signicant importance for industrial applications
of the hydrogenation of 3-HPA to 1,3-PDO, since a lower reac-
tion pressure implies lower requirements for both facilities and
energy consumption.
Scheme 1 Possible mechanism for the hydrogenation of 3-HPA to
1,3-PDO over the Ru–Ni/SiO2 catalyst.
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Fig. 7 Effect of reaction conditions on the hydrogenation of 3-HPA over the Ru–40Ni/SiO2 catalyst. (a) Reaction conditions: P ¼ 2.0 MPa, LHSV
¼ 0.73 hꢁ1; (b) reaction conditions: T ¼ 80 ꢂC, LHSV ¼ 0.73 hꢁ1; (c) reaction conditions: T ¼ 80 ꢂC, P ¼ 2.0 MPa; (d) reaction conditions: T ¼ 80 ꢂC,
P ¼ 2.0 MPa, LHSV ¼ 0.4 hꢁ1
.
Fig. 7c shows the effect of LHSV. It can be seen that the gradually, however, a ca. 70% yield of 1,3-PDO can be still
conversion of 3-HPA, selectivity to 1,3-PDO and yield of 1,3-PDO reached aer 132 h. The decrease in the yield of 1,3-PDO at
are all nearly 100% at LHSV ¼ 0.3 hꢁ1, and these decrease a relatively long TOS is due to the deposition of byproducts with
slightly in the range of LHSV ¼ 0.3–0.4 hꢁ1 and more obviously high molecular weights not only on the surface but also in the
at LHSV > 0.41 hꢁ1. This result indicates that a lower LHSV is pores of the catalyst, which was evidenced from the N2-phys-
favorable for the conversion of 3-HPA and the selectivity to 1,3- isorption determination (see Table 2).
PDO, and a higher LHSV, which corresponds to a shorter resi-
Table 4 lists a comparison of the yield of 1,3-PDO in this
dence time, leading to an insufficient contact between the work and those in the literature10,13 under different conditions.
reactants and catalyst, inhibiting the hydrogenation of 3-HPA to One can see that the Ru–40Ni/SiO2 catalyst employed in this
1,3-PDO.58 From the above results, it can be established that the work provided the largest yield of 1,3-PDO among all the other
optimized conditions for the hydrogenation of 3-HPA to 1,3- catalysts reported in the literature. Considering the extremely
PDO over the Ru–40Ni/SiO2 catalyst are temperature ¼ 80 ꢂC, H2 low pressure (2.0 MPa) and high yield of 1,3-PDO, the catalyst
pressure ¼ 2.0 MPa and LHSV ¼ 0.4 hꢁ1, considering the developed in this work can be reasonably expected to possess
production capacity, requirements for facilities, and energy a very large potential for its industrial application.
consumption.
Fig. 7d shows the yield of 1,3-PDO as a function of time on
4. Conclusions
stream (TOS). One can see that the yield of 1,3-PDO is initially
ca. 100% and this high level can be maintained for a TOS up to
60 h. On prolonging the TOS, the yield of 1,3-PDO decreases
The bimetallic Ru–Ni/SiO2 catalyst possessed different textural
and structural properties and presented an obviously high
performance for the hydrogenation of 3-HPA to 1,3-PDO, rela-
tive to the corresponding monometallic catalysts. This was
evidenced by the facts outlined as follows:
Table 4 Comparison between the results in this work and in the
(1) The introduction of Ru species increased the porosity of
the catalyst due to the formation of a Si–O–Ru–O–Si structure.
This favored both the diffusion of reactants and products and
provided more available active sites, and thus increased both
the yield of 1,3-PDO and the lifespan of the catalyst; (2) the
presence of Ru species decreased the average size of the Ni
particles and thus increased the degree of dispersion of Ni
species via promotion of the interaction between Ni and the
SiO2 support. This provided more active sites for the hydroge-
nation of 3-HPA to 1,3-PDO; (3) the great ability for the activa-
tion of H2 over the Ru species enabled the Ni species to be more
literature
Temperature
(ꢂC)
Pressure
(MPa)
Yield
(mol%)
Catalyst
Ref.
5% Ru/SiO2
10% Ru/
Al2O3
Ni/SiO2–
Al2O3
40
40
4.0
4.0
90.0
79.0
10
10
55
80
15.0
2.0
81.0
99.0
13
Ru–40Ni/
SiO2
This
work
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easily reduced at relatively low temperatures and also the active 18 S. Tada, R. Kikuchi, A. Takagaki, T. Sugawara, S. T. Oyama,
hydrogen to be generated via a hydrogen spillover process. This
K. Urasaki and S. Satokawa, Appl. Catal., B, 2013, 140–141,
258–264.
helped the Ni species to be stabilized in the Ni0 state and thus
increased both the conversion of 3-HPA and the selectivity to 19 A. Zhao, W. Ying, H. Zhang, H. Ma and D. Fang, Catal.
1,3-PDO; (4) the Ru–40Ni/SiO2 provided a yield above 99.0% of Commun., 2012, 17, 34–38.
1,3-PDO at 2.0 MPa of H2 pressure, with this high level of yield 20 C. Crisafulli, S. Scire, S. Minico and L. Solarino, Appl. Catal.,
being maintained for at least 60 h. A, 2002, 225, 1–9.
In summary, the Ru–Ni/SiO2 catalyst exhibited several 21 C. Crisafulli, S. Scire, R. Maggiore, S. Minico and
merits, such as a high yield of 1,3-PDO, a relatively long life- S. Galvagno, Catal. Lett., 1999, 59, 21–26.
span, a low operation pressure of H2 and a small consumption 22 M. Cerro-Alarcon, A. Maroto-Valiente, I. Rodrıguez-Ramos
of noble metal (1 mol% Ru). This enabled the Ru–Ni/SiO2 and A. Guerrero-Ruiz, Appl. Catal., A, 2004, 275, 257–269.
catalyst to be superior to other catalysts for the hydrogenation 23 A. Romero, A. Nieto-Marquez and E. Alonso, Appl. Catal., A,
`
`
`
`
´
´
´
of 3-HPA to 1,3-PDO reported in the literature and thus
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24 S. Wang, Q. Yin, J. Guo, B. Ru and L. Zhu, Fuel, 2013, 108,
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25 K. Mori, K. Miyawaki and H. Yamashita, ACS Catal., 2016, 6,
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Acknowledgements
This work was supported by the National Natural Science 26 D. L. Li, I. Atake, T. Shishido, Y. Oumi, T. Sano and
Foundation of China (Grant No. 21376068), Program for New
K. Takehira, J. Catal., 2007, 250, 299–312.
Century Excellent Talents in University, the Ministry of Educa- 27 G. Oh, S. Y. Park, M. W. Seo, Y. K. Kim, H. W. Ra, J.-G. Lee
tion of P. R. China, and the Program for Fu-Rong Scholar in
Hunan Province, P. R. China.
and S. J. Yoon, Renewable Energy, 2016, 86, 841–847.
28 X. K. Li, W. J. Ji, J. Zhao, S. J. Wang and C. T. Au, J. Catal.,
2005, 236, 181–189.
29 V. V. Kaichev, A. Y. Gladky, I. P. Prosvirin, A. A. Saraev,
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