Raney Ni-Si catalysts for selective hydrogenation of highly concentrated 2-butyne-1,4-diol to 2-butene-1,4-diol

Article abstract of DOI:10.1007/s10562-014-1259-8

Raney Ni-Si catalysts were synthesized by treating Raney Ni with silane in a fluidized bed reactor and tested in the selective hydrogenation of 2-butyne-1,4-diol (BYD) at high concentration. Structural characterizations including XRD patterns, TEM images, and X-ray photoelectron spectroscopy show that Raney Ni-Si catalysts are composed of a Ni core surrounded by nickel silicides. These species transform from Ni-rich silicide (Ni₂Si) to Si-rich silicide (NiSi₂) with increasing silicification temperature from 250 °C to 450 °C. The insertion of Si atoms into Raney Ni catalysts decreased the catalytic activity, but significantly improved the selectivity to 2-butene-1,4-diol (BED). The beneficial effect of Si on the selectivity hydrogenation of BYD may be caused by the presence of Si at Ni-defect sites, and the formation of the surface nickel silicide that suppress the further hydrogenation of BED. Compared with the traditional Lindlar-type catalysts, such Raney Ni-Si materials can be used extensively in organic synthesis for selective hydrogenation of alkynes, avoiding the associated hazards of toxic additives.

Full text of DOI:10.1007/s10562-014-1259-8

Catal Lett
DOI 10.1007/s10562-014-1259-8
Raney Ni–Si Catalysts for Selective Hydrogenation of Highly
Concentrated 2-Butyne-1,4-diol to 2-Butene-1,4-diol
Xiao Chen
Christopher T. Williams
•
Mingming Zhang
•
•
Kaixuan Yang
•
Changhai Liang
Received: 23 March 2014 / Accepted: 14 April 2014
Ó Springer Science+Business Media New York 2014
Abstract Raney Ni–Si catalysts were synthesized by
treating Raney Ni with silane in a fluidized bed reactor and
tested in the selective hydrogenation of 2-butyne-1,4-diol
1 Introduction
The hydrogenation of 2-butyne-1,4-diol (BYD) is an
industrially important method for the production of
2-butene-1,4-diol (BED) which can be further hydroge-
nated to 1,4-butanediol (BDO). BED is an important
intermediate in the production endosulfan [1], and vita-
mins A and B6 [2], as well as in the synthesis of
n-methyl pyrrolidione [3]. It is also used as an additive in
the paper and textile industries and in the resin manu-
facture [4]. BDO also has a variety of applications such
as in the preparation of polyurethane foams and poly-
butylene terephthalate (PBT) polyesters as well as in the
preparation of chemicals such as tetrahydrofuran,
c-butyrolactone, etc. [5, 6].
Traditionally, a large number of catalysts for selective
hydrogenation of BYD mainly include supported Pd and
Ni-based materials, but there are many existing problems
[1, 7, 8]. Pd-supported catalysts have high activity for BYD
hydrogenation, but low selectivity to BED. The higher
selectivity to BED can be obtained either by employing a
combination of Pd with one or more mixed compounds of
Cu, Zn, Pb, Ca, Cd, Ga, etc. or in the presence of organic
bases such as pyridine, quinoline or isoquinoline [9–11]
Unfortunately, the conversion of the hydrogenation of
BYD was significantly decreased and the Pd-based cata-
lysts were easily deactivated due to aggregation of the
metal particles. The poisons (i.e., organic bases) also need
to be completely removed in order to obtain the highest
purity of the product for fine chemical and pharmaceutical
applications [12]. Ni-supported catalysts and Raney Ni
catalysts can also hydrogenate BYD to BED or BDO, but
they are not satisfactory due to their low activity and
selectivity and deactivation. The structural and textural
properties of Ni-based catalysts are changed rapidly during
(
BYD) at high concentration. Structural characterizations
including XRD patterns, TEM images, and X-ray photo-
electron spectroscopy show that Raney Ni–Si catalysts are
composed of a Ni core surrounded by nickel silicides.
These species transform from Ni-rich silicide (Ni Si) to Si-
2
rich silicide (NiSi ) with increasing silicification tempera-
2
ture from 250 °C to 450 °C. The insertion of Si atoms into
Raney Ni catalysts decreased the catalytic activity, but
significantly improved the selectivity to 2-butene-1,4-diol
(
BED). The beneficial effect of Si on the selectivity
hydrogenation of BYD may be caused by the presence of
Si at Ni-defect sites, and the formation of the surface nickel
silicide that suppress the further hydrogenation of BED.
Compared with the traditional Lindlar-type catalysts, such
Raney Ni–Si materials can be used extensively in organic
synthesis for selective hydrogenation of alkynes, avoiding
the associated hazards of toxic additives.
Keywords Raney Ni–Si ꢀ Silicification ꢀ 2-Butyne-1,4-
diol ꢀ Selective hydrogenation
X. Chen ꢀ M. Zhang ꢀ K. Yang ꢀ C. Liang (&)
Laboratory of Advanced Materials and Catalytic Engineering,
Dalian University of Technology, Dalian 116024, China
e-mail: changhai@dlut.edu.cn
URL: http://finechem.dlut.edu.cn/liangchanghai
C. T. Williams
Department of Chemical Engineering, University of South
Carolina, Columbia, SC 29208, USA
123

X. Chen et al.
hydrogenation of BYD in aqueous solution [13, 14]. In
addition, all the above processes for the hydrogenation of
BYD suffer from high temperatures, pressures, and for-
mation of side products. The formation of side products
and residues affects the efficiency of the process. In par-
ticular, the reported processes focus on catalytic conversion
of a low concentration of BYD (\10 wt%) [4, 7, 15],
which led to high energy consumption and difficulty of
products separation. Obviously, increasing the concentra-
tion of BYD is highly demanded both from the perspective
of enhancing production capacity and reducing the energy
consumption. As such, more effective catalytic materials
that can afford high BED selectivity under mild conditions
are needed for selective hydrogenation of BYD.
silicification temperatures for 15 min. When the reaction
ended, SiH flow was first stopped and then the product
4
was cooled down to room temperature (RT) in H2
(30 sccm) and passivated in 1 % O /Ar overnight. The
2
obtained solids were designated as Raney T -Ni–Si,
s
where T referred to the silicification temperature. The
s
exhaust gas should be absorbed by water or alkali liquor
during the silicification process.
2.2 Characterization
Nitrogen adsorption and desorption isotherms were con-
structed using the multi-point method at -196 °C, and
were measured using a Micrometrics 2020. Prior to the
measurements, all samples were degassed completely at
Dopant Si can alter the metal coordination in transition
metal silicides, leading to the downshift of the d band
center and a strong modification of the electronic structure
around the Fermi level. Interstitial silicides of early tran-
sition metals have specific physical and chemical proper-
ties, such as good electrical conductivity, high chemical
inertness, thermal stability, and superior resistance to H2S
poisoning [16, 17]. In our previous research, supported
cobalt silicide catalysts showed high catalytic activity and
selectivity in naphthalene hydrogenation [18]. Bulk nickel
silicide catalysts showed excellent selectivity for the
hydrogenation of phenylacetylene to styrene (ca. 93 %)
due to the strong modification of electronic structure
derived from the interaction of nickel and silicon [19, 20].
Given these promising results, the use of metal silicides for
the selective hydrogenation of BYD was indicated.
-
3
200 °C in a vacuum of 10 Torr for at least 4 h. Surface
areas were calculated from the linear part of the Brunauer–
Emmet-Teller (BET) plot.
X-ray diffraction (XRD) analyses of the samples were
carried out using a Rigaku D/Max-RB diffractometer with
a Cu K monochromatized radiation source, operated at
a
40 kV and 100 mA. The average size of nickel silicide
particles was evaluated by the Scherrer formula as:
0
:9kKa1
L ¼ B
ð1Þ
cos hmax
ð2hÞ
˚
where kKa is 1.54178 A, and B(2h) is the full width at half-
maximum of the diffraction peak in radians.
1
The particle size distribution of the samples was ana-
lyzed by transmission electron microscopy (TEM) (Tecnai
G220 S-Twin, 200 kV). Energy dispersive X-ray spec-
troscopy (EDX) was also performed using the same
instrument. Elemental mapping was conducted under
STEM mode with the EDX detector as recorder.
In this work, we report the preparation and character-
ization of Raney Ni–Si materials, and their evaluation as
catalysts for the hydrogenation of high concentrated BYD
(
20 wt% in water) in the fixed bed reactor under mild
conditions. The results demonstrate that the addition of Si
to Raney Ni catalysts significantly improved the selectivity
to BED. The electronic modification and isolation of active
sites of Raney Ni–Si have a significant impact on their
catalytic properties.
The chemisorption of CO was carried out on a Mi-
cromeritics AutoChem II 2920 Automated Catalyst Char-
acterization System. About 0.10 g of a passivated sample
was in situ reduced in H
at 400 °C for 2 h and then cooled
2
to room temperature in a He stream. The sample was
pulsed with 5 % CO/He, which was not stopped until the
CO peak area was constant. The CO uptake was obtained
by the measuring the accumulated adsorbed CO. It was
assumed that the adsorption stoichiometriy is CO:Ni = 1
for all the samples.
2
Experimental
2
.1 Preparation of Raney Ni–Si Catalyst
Surface compositions were investigated by X-ray pho-
toelectron spectroscopy (XPS) employing an ESCA-
Typically, 0.30 g Raney Ni was reduced in 1 atm H at
2
2
00 °C for 1 h. The reduced samples were increased to
the silicification temperature under the same flow
30 sccm). Because SiH is explosive, experiments should
LAB250 (Thermo VG, USA) spectrometer with Al K
a
(1,486.6 eV) radiation with a power of 150 W. Survey and
individual high-resolution spectra were recorded with a
pass energy of 50 eV. Ni 2p, Si 2p, and O 1s lines were
monitored. All core-level spectra were referenced as the C
1s neutral carbon peak at 284.6 eV and were deconvoluted
into Gaussian component peaks. After calibration, the
(
4
be carried out cautiously. The H2 flow was 90 sccm,
while the Si source (SiH ) was introduced into the reactor
4
at a flow rate of 10 sccm. The resulting Ni sample was
reacted with the 10 % SiH /H2 mixture at various
4
1
23

Raney Ni–Si Catalyst for Selective Hydrogenation of BYD
background from each spectrum was subtracted using a
Shirley-type background.
(a)
Raney 450-NiSix
2
.3 Hydrogenation Reaction
NiSi 43-0989
2
The catalytic properties of Raney Ni–Si catalysts were
tested in the hydrogenation of highly concentrated BYD in
aqueous phase at identical conditions, i.e., reactor tem-
peratures of 50, 70, 90, 110, and 130 °C, system pressure
of 3.0 MPa, liquid hourly space velocity (LHSV) of
Raney 350-NiSix
-
1
2
4 h , and an H -to-liquid feed ratio (VH2/oil) of 600. The
2
NiSi 38-0844
passivated catalysts (0.20 g, diluted with quartz to 5 mL)
Raney 250-NiSix
were activated in situ with H (48 sccm) at 400 °C for 2 h.
2
The reaction was carried out in a high pressure fixed bed
continuous flow stainless steel catalytic reactor with an
interior placed thermocouple. The liquid reactant was
composed of 4 wt% 1,2-propylene glycol (as internal
standard), 20 wt% BYD reactant, and 76 wt% water (as
solvent). The reaction product was analyzed by off-line gas
chromatography (Bruker 450-GC) equipped with an FFAP
capillary column (30 m 9 0.32 mm 9 0.5 lm) and a
flame ionization detector.
Ni Si 48-1339
2
Raney Ni
Ni 04-0850
10
20
30
40
50
60
70
80
90
2
Theta (deg.)
3
Results and Discussion
(b)
3
.1 Preparation of Raney Ni–Si Catalyst
6
0 min
0 min
The XRD patterns of Raney Ni–Si samples prepared at
3
various silicification temperatures from 250 to 450 °C for
1
5 min are displayed in Fig. 1a. The crystalline phases
15 min
were identified by comparing with JCPDS files (Ni, cubic,
No. 04-0850; Ni Si, orthorhombic, No. 48-1339; NiSi,
2
orthorhombic, No. 38-0844; NiSi , cubic, No. 43-0989).
2
10 min
The patterns clearly show the typical diffraction peaks at
4
4.51°, 51.85°, and 76.37°, which are due to cubic phase
nickel. As shown in the XRD pattern of Raney 250-NiSix
1
0
20
30
40
50
60
70
80
90
2Theta (deg.)
sample, the diffraction peaks of Ni Si at 32.48°, 45.50°,
and 48.76° have emerged, indicating Raney Ni is modified
by Ni-rich silicide (Ni Si). With increasing silicification
2
Fig. 1 a XRD patterns of Raney Ni–Si prepared at silicification
temperature from 250 to 450 °C for 15 min. b XRD patterns of Raney
Ni–Si prepared at silicification temperature 450 °C for 10, 15, 30, and
2
temperature, diffraction peaks at 23.13°, 31.59°, 47.33°,
and 51.44° are observed, which can be attributed to the
6
0 min, respectively
transformation of Ni Si to NiSi. When the silicification
2
temperature increased to 450 °C, four new diffraction
peaks at 28.60°, 47.41°, 56.33°, and 76.59° were observed,
450 °C, respectively, which are higher than that of Raney
Ni (6.0 nm) based on calculations using the Scherrer
equation (as shown in Table 1). Thus, the higher silicifi-
cation temperature appears to lead to sintering of the Raney
Ni–Si particles.
assigned to cubic phase NiSi . Therefore, with increasing
2
silicification temperature, Ni-rich silicide modified Raney
Ni has been transformed to Si-rich modified Raney Ni.
However, Raney Ni was not converted into nickel silicide
completely during the silicification process for 15 min. A
nickel silicide shell is formed around the Ni core. In
addition, the particle size of the Raney Ni–Si is 7.2, 7.4,
and 9.3 nm for the Raney Ni silicified at 250, 350, and
To confirm further these structural changes of Raney
Ni–Si, Fig. 1b shows the XRD patterns of Raney Ni–Si
prepared at a silicification temperature of 450 °C for 10,
15, 30, and 60 min. With increasing silicification time, the
diffraction peak intensity of Ni was gradually weakened,
123

X. Chen et al.
Table 1 Phase composition
and texture of the Raney Ni–Si
Sample
Phases
Ni
Surface area
(
Pore volume
3
(cm /g)
CO chemisorption
(lmol/g)
Crystallite
size (nm)
2
m /g)
Raney Ni
64
21
35
43
0.070
0.035
0.056
0.063
102.2
103.6
112.9
107.1
6.0
7.2
7.4
9.3
Raney 250-NiSi
Raney 350-NiSi
Raney 450-NiSi
x
x
x
2
Ni, Ni Si
Ni, NiSi
Ni, NiSi
2
(
a) 80
(b) 0.015
Raney 450-NiSix
0
.014
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
Raney 350-NiSix
Raney 250-NiSix
Raney Ni
0
.013
0
0
0
0
0
0
0
0
0
0
0
0
0
.012
.011
.010
.009
.008
.007
.006
.005
.004
.003
.002
.001
.000
0
.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
0
2
4
6
8 10 12 14 16 18 20
Ralative Pressure (P/Pº)
Pore Width (nm)
Fig. 2 a N adsorption/desorption isotherms at -196 °C of the Raney Ni–Si samples. b Pore size distribution of the samples calculated from the
2
desorption branch of the isotherms using the DFT method
while the intensity of NiSi was increased. However, the Ni
2
observed at about 4.0 nm, which decreased firstly and then
increased with increasing silicification temperature. However,
new mesopores with size around 3.0 nm emerged. This indi-
cates that Si atom-doping into the Ni lattices leads to lattice
expansion that produces new porosity. As shown inTable 1,the
phase was still present, even though the silicification time
was extended to 60 min. The formation of Raney Ni–Si
mainly includes two typical steps: the catalytic decompo-
sition of SiH to Si atoms and the diffusion of Si atoms into
4
2
metallic Ni lattices. When the stable NiSi shell formed on
2
surface area decreased from 64 to 21 m /g and then increased to
2
43 m /g, and the pore volume decreased from 0.070 to
the surface of Raney Ni, the diffuse of Si atoms into the
Raney Ni core will be suppressed to some extent [21]. In
3
3
0.035 cm /g and then increased to 0.063 cm /g after the
reduction and silicification of Raney Ni. The reduction of Ra-
ney Ni leads to the collapse of skeletal Ni [24]. However, after
increasing the silicification temperature from 250 to 450 °C, the
surface area and pore volume increased. This is attributed to Si
atoms doping into the Raney Ni and enlarging the pores.
In addition, CO chemisorption results for Raney Ni–Si
are also presented in the Table 1. Addition of Si to the
Raney-Ni catalyst increased the irreversible extent of CO
chemisorption from 102.2 to 112.9 lmol/g, and then
decreased to 107.1 lmol/g. Adsorption of CO on Ni(111)
is favored at threefold hollow sites [25]. Our observation
that addition of Si to Raney Ni causes an increase in the
CO uptake is consistent with the report that adsorption of
CO is strengthened on isolated Ni atoms. The stoichiom-
etry changes from Ni3–CO to Ni–CO with Si addition. This
addition, the Si atoms are easily oxidized to SiO passiv-
2
ation layer after the sample is exposed to air [22].
Figure 2a shows the N adsorption–desorption isotherms of
2
Raney Ni precursor and Raney Ni–Si samples after silicifica-
tion at different temperatures. The corresponding structural
parameters are summarized in Table 1. All adsorption–
desorption isotherms show type IV behavior with an H1 hys-
teresis loop according to IUPAC classification, indicating a
narrow mesopore size distribution [23]. With increasing silic-
ification temperature, the structure of Raney Ni has been
destroyed firstly in the reduction process, and then some new
mesopores were formed due to the Si atoms doping into the Ni
lattices. Figure 2b shows the pore size distribution of the
samples calculated from the desorption branch of the isotherms
using the DFT method. The mesopore size of Raney Ni was
1
23

Raney Ni–Si Catalyst for Selective Hydrogenation of BYD
Fig. 3 SEM image and maps of Raney 350-NiSi
Fig. 4 a TEM and b HRTEM
x
and the corresponding electron diffraction pattern
(
a)
(b)
images of Raney 350-NiSi
sample
x
d=0.329 nm
Ni Si (101)
2
phenomenon can be analogous to the enhancing of CO
adsorption on Pd surfaces caused by Ga species [26]. The
phase transformation of nickel silicides lead to the varia-
tion of geometric construction and electronic structure,
affecting the CO chemisorption of nickel silicides [27].
uniformly dispersed. The EDX spectra confirm the exis-
tence of Ni, Al, and Si elements in the sample. The
Ni:Al:Si ratio is about 4:1:1. While samples handled in
air are likely to show O contamination, homogeneous Ni,
Al, and Si distributions were found in the passivated
The SEM image and maps of Raney 350-NiSi and the
x
Raney 350-NiSi sample, as seen in the corresponding
x
corresponding electron diffraction pattern are presented in
elemental maps, indicating the Si atoms are uniformly
doped into the lattice of Raney Ni. In order to investigate
Fig. 3. Clearly, the Raney 350-NiSi fine particles are
x
123

X. Chen et al.
Fig. 5 XPS of a Ni 2p
region, b Al 2p region, and
c Si 2p region of Raney
Ni–Si catalysts
(a)
Raney 450-NiSix
852.8 eV
Raney 350-NiSix
856.4 eV
Raney 250-NiSix
Raney Ni
866
864
862
860
858
856
854
852
850
848
Binding Energy (eV)
(b) Raney 450-NiSix
(c) Raney 450-NiSxi
72.4 eV
99.5 eV
74.3 eV
103 eV
Raney 350-NiSix
Raney 350-NiSxi
Raney 250-NiSix
Raney 250-NiSix
Raney Ni
77
76
75
74
73
72
71
108
106
104
102
100
98
96
Binding Energy (eV)
Binding Energy (eV)
the structural properties and the composition distribution,
TEM and HRTEM were carried out. The representative
low magnification TEM image of the Raney 350-NiSix
sample is shown in Fig. 4. It can be seen that the Raney
Ni–Si nanocrystals are aggregated to some degree. The
HRTEM image of the Raney 350-NiSix sample
demonstrates the formation of the nickel silicide overlay
on the surface of Raney Ni, i.e., the lattice spacing of
0.329 nm corresponds to that of (101) planes of Ni Si
2
[28].
Figure 5 shows the XPS spectra of the Raney Ni–Si
sample without and with treating at silicification
1
23

Raney Ni–Si Catalyst for Selective Hydrogenation of BYD
1
00
100
interaction between Si and Al and the formation of Al–O–
Si on the surface of Raney Ni–Si samples. In addition,
9
8
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
0
90
larger amounts of oxidized Si (SiO , BE 101–104 eV) and
x
80
70
60
50
40
30
20
10
0
smaller amounts of silicon in the intermetallic Ni–Si
0
compounds (Si , BE 99.5 eV) species were observed at the
Si 2p level. This is in accordance with theoretical predic-
tions that the metal with lower sublimation energy is
concentrated at the surface on binary alloys [31]. Mean-
while, nickel is protected from oxidation by a passive
aluminum oxide and silica film, which will influence the
catalytic activity of Raney Ni–Si samples.
Others
BOL
2
-OH-THF
BDO
BED
3.2 Hydrogenation of 2-Butyne-1,4-diol over Raney
6
0
70
80
90
100
110
120
130
140
Ni–Si Catalyst
Temperature (ºC)
Fig. 6 Conversion of BYD and product selectivity as a function of
temperature on stream over Raney 350-NiSi catalysts. (The reaction
was carried out at 3.0 MPa H containing a catalyst with 0.20 g, 20 %
BYD in water, and contact time 11.6 gcat. h mol
3
.2.1 Effect of the Reaction Temperature
x
2
-
1
)
The hydrogenation activities of the as-prepared Raney Ni–
Si catalysts were tested in the aqueous phase selective
hydrogenation of highly concentrated BYD. Figure 6
shows the conversion of BYD and product selectivity at the
Table 2 Activities and selctivities of Raney Ni–Si catalysts for the
hydrogenation of 2-butyne-1,4-diol measured at 90 °C, 3 MPa H
and contact time 11.6 gcat. h mol
2
,
-1
-1
contact time 11.6 gcat. h mol as a function of tempera-
ture on stream over Raney 350-NiSi catalyst. The con-
x
Catalyst
Conversion
mol%)
TOFs
Selectivity (mol%)
BED BDO Others
version of BYD increased from 50.5 to 99.3 % with
increasing reaction temperature from 70 to 130 °C. How-
ever, the selectivity to 2-butene-1,4-diol (BED) decreased
from 80.3 to 12.6 % and the selectivity to further hydro-
genation products (1,4-butanediol (BDO) and 2-OH-THF)
increased with increasing reaction temperature. The higher
reaction temperature enhanced the reaction rates and con-
version of the intermediate product to the undesired one,
leading to that the over hydrogenation of BED to BDO, as
well as other side reactions. The by-products include
-
(s )
1
(
Raney Ni
Raney
96.7
81.3
14.7
12.2
67.3 8.1
82.5 4.6
24.6
12.9
2
50-NiSi
x
x
x
Raney
3
84.8
35.7
11.6
5.2
80.4 9.3
89.7 2.1
10.3
8.2
50-NiSi
Raney
4
50-NiSi
2-hydroxy THF, butanol, and condensation product.
temperatures from 250 to 450 °C for 15 min. The XPS
spectra at the Ni 2p level have been deconvoluted into
Gaussian component peaks by XPSPeak software. The Ni
When the reaction temperature is 90 °C and contact
-
1
time 11.6 gcat. h mol , the conversion of BYD over
Raney Ni and Raney Ni–Si prepared at the silicification
temperature at 250, 350, and 450 °C is 96.7, 81.3, 84.8, and
35.7 %, respectively, as shown in Table 2. The TOFs of
BYD during the hydrogenation over Raney Ni–Si catalysts
2
8
p peaks of the Raney Ni sample at 825.8, 856.4, and
62.5 eV are attributed to metallic Ni in Ni–Al alloy
0
denoted as Ni ), NiO, and the satellite peak, respectively.
(
-
1
The NiO peak was also observed because the sample was
oxidized when it was exposed to air. After the reduction
and silicification, the peak due to metallic Ni shifted to
higher binding energy, which is attributed to the covalent
interactions between Ni and Si, further demonstrating the
formation of nickel silicide [29]. With increase of the
temperature to 450 °C, the peak at 853.6 eV due to the
NiSi2 phase can be observed in the Raney 450-NiSix
sample. At the Al 2p level, two peaks around BE values of
decreased from 14.7 to 5.2 s with the increasing silici-
fication temperature. The activity of Raney Ni–Si catalysts
were lower than that of Raney Ni, which can be attributed
to the formation of passive silica on the surface of Raney
Ni–Si that inhibits the catalytic activity. The structure has
been confirmed by the XPS results. However, the selec-
tivity of BED over Raney 250-NiSi , Raney 350-NiSi , and
x
x
Raney 450-NiSix catalyst is 82.5, 80.4, and 89.7 %,
respectively, which is much more than that of Raney Ni
catalyst (67.3 %). This indicates that the presence of Si at
7
2.4 and 74.3 eV represent metallic aluminum and the
aluminum oxide, respectively [30]. With increasing of
silicification temperature, the peak due to aluminum oxide
shifted to lower bonding energy, which is attributed to the
Ni-defect sites and the formation of Ni–Si alloy (Ni Si,
2
NiSi, and NiSi ) surfaces promoted selective hydrogena-
2
tion of BYD, and suppressed the hydrogenation of BED.
123

X. Chen et al.
a) 100
(b)100
100
(
8
6
4
2
0
0
0
0
0
80
80
60
40
20
0
60
40
20
0
Raney Ni
Raney 250-NiSix
Raney 350-NiSix
Raney 450-NiSix
Raney Ni
Raney 250-NiSix
Raney 350-NiSix
Raney 450-NiSix
2
4
6
8
10
12
14
16
18
2
4
6
8
10
12
14
16
18
-1
Contact time (gcat.⋅h⋅mol-1)
Contact time (gcat.⋅h⋅mol )
Fig. 7 Conversion of BYD and selectivities to BED and BDO versus the contact time at 3 MPa H
2
and 90 °C over Raney Ni–Si catalysts
a)100
(b)100
(
BYD
BDO
BOL
BED
2-OH-THF
Others
8
6
4
2
0
0
0
0
0
80
BED
BAD
60
40
20
0
2-OH-THF
BOL
Others
0
2
4
6
8
10
12
14
16
18
2
4
6
8
10
12
14
16
18
-1
Contact time (gcat.⋅h⋅mol-1)
Contact time (gcat.⋅h⋅mol )
Fig. 8 Product selectivities of the hydrogenation of BYD versus the contact time at 3 MPa H
2
and 90 °C over Raney 350-NiSi
x
catalyst
Scheme 1 Reaction network of
-butyne-1,4-diol (BYD)
hydrogenation over Raney Ni–
Si catalysts
OH
OH
HO
HO
2-butyne-1,4-diol (BYD)
OH
2
HO
2
-butene-1,4-diol (BED)
butane-1,4-diol (BDO)
O
O
OH
HO
4
-hydroxybutanal
tetrahydrofuran-2-ol (2HTHF)
The phenomenon is similar with the continuous semihy-
drogenation of phenylacetylene over an amorphous Pd81-
Si19 catalyst [32]. Compared with the traditional Lindlar-
type catalysts, such Raney Ni–Si materials can be used
extensively in organic synthesis for selective hydrogena-
tion of alkynes, in which the doped Si atoms partially tuned
the metal sites, but without the associated hazards of toxic
heavy metals such as lead being present [33].
3.2.2 Effect of Contact Time
With the purpose of determining the product distribution
with the contact time on stream, Fig. 7 shows that con-
version of BYD and selectivities to BED and BDO versus
the contact time at 3 MPa H
and 90 °C over Raney Ni–Si
catalysts. Over the Raney Ni–Si catalysts, the conversion
2
of BYD was lower than it was over Raney Ni catalyst.
1
23

Raney Ni–Si Catalyst for Selective Hydrogenation of BYD
Because the Si atoms doped into the lattice of Raney Ni
reduced the activity for hydrogenation of BYD to some
extent. However, the selectivity to BED over Raney Ni
catalyst decreased from 90.0 to 42.1 % with increasing
References
1
2
. Winterbottom JM, Marwan H, Viladevall J, Sharma S, Rayma-
shasay S (1997) Stud Surf Sci Catal 108:59
. Chaudhari RV, Jagernathan R, Kolhe DS, Erning G, Hofman H
(1987) Appl Catal A 29:141
-
1
contact time from 2.9 to 17.4 gcat. h mol . But the
selectivity to BED over Raney Ni–Si catalysts were always
higher than 70 % with increasing contact time, which much
high than that of Raney Ni catalyst. The formation of
nickel silicides on the surface of Raney Ni suppressed the
further hydrogenation of BED.
3. Chaudhari RV, Rode CV, Jaganathan R, Telkar MM, Rane VHEP
2002) Patent EP1207146
. Telkar MM, Rode CV, Rane VH, Jaganathan R, Chaudhari RV
2001) Appl Catal A 216:13
(
4
5
(
. Weissermel K, Arpe HJ (1994) Industrielle Organische Chemie.
VCH Verlagsge-sellschaft, Weinheim
6
7
8
. Harris N, Tuck MW (1990) Hydrocarb Process 69:79
. Zhao FY, Ikushima Y, Arai M (2003) Green Chem 5:656
. Appleyard CJS, Gartshore JFC (1946) BIOS Rep 367:22
Figure 8 presented that product selectivity of the
hydrogenation of BYD versus the contact time at 3 MPa H2
and 90 °C over the Raney 350-NiSi catalyst. At the low
x
9. Bruehwiler A, Semagina N, Grasemann M, Renken A, Kiwi-
Minsker L, Saaler A, Lehmann H, Bonrath W, Roessler F (2008)
Ind Eng Chem Res 47:6862
10. Chaudhari RV, Parande MG, Ramchandran PA, Brahme PH,
Vadgaonkar HG, Jaganathan R (1985) AIChE J 31:1891
1. Bollger G, Boer R, Wache W, Gratze H, Koerning W (1976)
German Patent 2451929
2. Wood J, Bodenes L, Bennett J, Deplanche K, Macaskie LE
contact time (i.e., lower conversions), the BYD hydroge-
nation produced primarily BED. The selectivity to BED is
-
1
ca. 85 % (contact time 2.9 gcat. h mol ). Once the BYD is
completely depleted with increasing the contact time, the
dominant species (BED) is hydrogenated to BDO or
isomerized into 4-hydroxybutanal. Furthermore, the cycli-
zation of 4-hydroxybutanal easily took place to produce
hemiacetal (2-OH-THF). The reaction network of BYD
hydrogenation over Raney Ni–Si is shown in Scheme 1.
Comparing among the Raney Ni–Si catalysts, it is further
demonstrated that the nickel silicides modified Raney Ni
improved the selectivity hydrogenation property of BYD
due to the stronger interaction between Ni and Si atoms.
1
1
1
(
2010) Ind Eng Chem Res 49:980
3. Bautista FM, Campelo JM, Garcia A, Guarde n˜ o R, Luna D,
Marinas JM (1991) Stud Surf Sci Catal 59:269
14. Tanielyan S, Schmidt S, Marin N, Alvez G, Augustine R (2010)
Top Catal 53:1145
5. Rode CV, Tayade PR, Nadgeri JM, Jaganathan R, Chaudhari RV
2006) Org Process Res Dev 10:278
6. Thomas H, Maugh II (1984) Science 225:403
17. Schmitt AL, Higgins JM, Szczech JR, Jin S (2010) J Mater Chem
0:223
1
(
1
2
1
1
2
8. Zhao AQ, Zhang XF, Chen X, Guan JC, Liang CH (2010) J Phys
Chem C 114:3962
9. Chen X, Zhao AQ, Shao ZF, Li C, Williams CT, Liang CH
4
Conclusions
(
2010) J Phys Chem C 114:16525
Raney Ni–Si catalysts have been synthesized by exposing
Raney Ni to volatile silane, in which the Si atoms doped
into the lattice of Raney Ni uniformly. However, Al and Si
relative to Ni with lower sublimation energy were found to
be concentrated at the surface on Raney Ni–Si and form a
passive aluminum oxide and silica film. In the selective
hydrogenation of highly concentrated BYD in a fixed bed
reactor, Raney Ni–Si had slightly lower catalytic activity
for hydrogenation of BYD, but significantly promoted the
selectivity to BED, compared with Raney Ni catalyst. The
presence of Si at Ni-defect sites and the formation of Ni–Si
alloy surfaces block sites for the BED to further hydroge-
nate. Compared with the traditional Lindlar-type catalysts,
such Raney Ni–Si materials can be used extensively in
organic synthesis for selective hydrogenation of alkynes, in
which the doped Si atoms partially tuned metal sites but
without the associated hazards of toxic additives.
0. Chen X, Li M, Guan JC, Wang XK, Williams CT, Liang CH
(2012) Ind Eng Chem Res 51:3604
1. Kang K, Kim SK, Kim CJ, Jo MH (2008) Nano Lett 8:431
2. Liu Z, Zhang H, Wang L, Yang D (2008) Nanotechnology
2
2
1
9:375602
2
2
2
3. Sing KSW, Everett DH, Haul RAW, Moscou L, Pierotti RA,
Rouquerol J, Siemieniewska T (1985) Pure Appl Chem 57:603
4. Mikkolaa JP, Vainioa H, Salmia T, Sj o¨ holmb R, Ollonqvistc T,
V a¨ yrynenc J (2000) Appl Catal A 196:143
5. Becker L, Aminpirooz S, Hillert B, Pedio M, Haase J, Adams DL
(
1993) Phys Rev B 47:9710
26. Kovnir K, Armbr u¨ ster M, Teschner D, Venkov TV, Jentoft FC,
Knop-Gericke A, Grin Y, Schl o¨ gl R (2007) Sci Technol Adv
Mater 8:420
2
7. Chen X, Liu X, Wang L, Li M, Williams CT, Liang CH (2013)
RSC Adv 3:1728
28. Song YP, Schmitt AL, Jin S (2007) Nano Lett 7:965
2
9. Chen X, Wang XK, Xiu JH, Williams CT, Liang CH (2012) J
Phys Chem C 116:24968
0. Yu XB, Li HX, Deng JF (2000) Appl Catal A 199:191
1. Lei H, Song Z, Tan DL, Bao XH, Mu XH, Zong BN, Min EZ
3
3
(
2001) Appl Catal A 214:69
Acknowledgments We gratefully acknowledge the financial support
provided by the National Natural Science Foundation of China
32. Tschan R, Wandeler R, Schneider MS, Chubert MM, Baiker A
(2001) J Catal 204:219
(
1
(
21373038), the China Postdoctoral Science Foundation (2014M55
068), and the Fundamental Research Funds for the Central Universities
DUT12YQ03 and DUT14RC(3)007).
33. Bennett JA, Attard GA, Deplanche K, Casadesus M, Huxter SE,
Macaskie LE, Wood J (2012) ACS Catal 2:504
123