Nickel-aluminum intermetallic compounds as highly selective and stable catalysts for the hydrogenation of naphthalene to tetralin

Article abstract of DOI:10.1002/cctc.201402957

Selective hydrogenation of naphthalene to tetralin was conducted by using Ni-Al intermetallic compounds (IMCs) prepared by a chemical synthetic route. Ni-Al IMC catalysts achieved a lasting high conversion with 100% selectivity up to 125 h. During the syn

Full text of DOI:10.1002/cctc.201402957

DOI: 10.1002/cctc.201402957
Full Papers
Nickel–Aluminum Intermetallic Compounds as Highly
Selective and Stable Catalysts for the Hydrogenation of
Naphthalene to Tetralin
Xiao Chen, Yue Ma, Lei Wang, Zonghan Yang, Shaohua Jin, Liangliang Zhang, and
[a]
Changhai Liang*
Selective hydrogenation of naphthalene to tetralin was con-
ducted by using Ni–Al intermetallic compounds (IMCs) pre-
pared by a chemical synthetic route. Ni–Al IMC catalysts ach-
ieved a lasting high conversion with 100% selectivity up to
than that of metallic Ni and other Ni–Al IMCs (Ni Al and Ni Al ).
3 2 3
The results can be understood by a combination of site isola-
tion and alteration of the electronic structure by chemical
bonding. Ni atoms are scattered and spatially isolated by Al
atoms, which in turn resists carbon deposition. The findings
provide a useful approach to tailor the catalytic properties of
transition metals by formation of IMCs, which could be appli-
cable in heterogeneous catalysis.
125 h. During the synthesis process, the Ni–Al IMCs underwent
the following phase transformation as a function of the con-
tent of the Al source (LiAlH ): Ni(cubic)!Ni Al(tetragonal)!
4
3
NiAl(cubic)!Ni Al (hexagonal). In the selective hydrogenation
2
3
of naphthalene, the catalytic activity of NiAl was much higher
Introduction
Tetralin, a useful high-boiling-point solvent, has been widely
used in paints, coatings, inks, pharmaceuticals, and paper, and
states and the transition-metal d states, transition-metal alumi-
nides with a special geometry and electronic structure have
[
1]
[10–14]
it has additionally been used as a hydrogen donor. It can be
synthesized simply through the semihydrogenation of naph-
potential applications in catalysis.
Ganem and Osby re-
viewed the applicability of metal aluminide catalysts in some
typical organic reactions, which laid the foundation for the ra-
tional design of efficient aluminide compounds as new catalyt-
[
2,3]
thalene.
The heterogeneous hydrogenation of naphthalene
is not only a useful model reaction that can be used to gauge
the activity of metal catalysts, but it is also of industrial impor-
[11]
ic materials. Recently, on the basis of the theory of site isola-
tion and alteration of the electronic structure by chemical
bonding, Armbrꢀster et al. successfully synthesized the noble-
metal-free and environmentally benign IMCs Al Fe and
[
4]
tance in upgrading coal liquids and diesel fuels. This process
not only improves the stability of fuels, but it also reduces
emissions of harmful solid particles. Traditionally, transition-
metal sulfide catalysts have low activity and need high opera-
tion temperatures owing to thermodynamic limitations of the
13
4
Al Co , which were identified as potent and low-costing re-
13
4
placements for Pd-based hydrogenation catalysts in the partial
[
5]
[12,13]
hydrogenation of aromatics. In addition, noble-metals cata-
lysts exhibit high activity, but they are always limited in their
application because of their high price and poisoning of their
hydrogenation of acetylene.
Subsequently, Piccolo further
confirmed that Al Fe was a selective hydrogenation catalyst
13
4
for butadiene at room temperature under well-defined ultra-
[
6]
[14]
active sites by sulfur, nitrogen, and carbon atoms. Therefore,
the development of highly active catalysts with long-term sta-
bility for the selective hydrogenation of naphthalene is of
high vacuum conditions.
Unfortunately, preparation meth-
ods for aluminides including the use of high-energy solids and
interface reactions inherited from the ceramic industry result in
big particle sizes and low surface areas. The controlled synthe-
sis of a high surface area or well-dispersed metal aluminides
still remains an important challenge for catalytic applications.
Herein, we report the synthesis of nanocrystalline nickel alumi-
nides that exhibit excellent selectivity and long-term stability
in the selective hydrogenation of naphthalene.
[
7]
great importance.
Intermetallic compounds (IMCs), such as transition-metal alu-
minides, are between metal alloys and ionic compounds; they
exhibit unique physical and chemical properties (high melting
[
8,9]
point, low density, and high corrosion resistance).
Owing to
charge transfer and hybridization between the Al s and p
[
a] Dr. X. Chen, Y. Ma, L. Wang, Z. Yang, S. Jin, L. Zhang, Prof. C. Liang
Laboratory of Advanced Materials and Catalytic Engineering
School of Chemical Engineering
Results and Discussion
Dalian University of Technology
Dalian 116024 (P.R. China)
E-mail: changhai@dlut.edu.cn
The Ni–Al phase diagram contains five IMCs: Ni Al, Ni Al , NiAl,
3
5
3
Ni Al , and NiAl . Ideally, the specific intermetallic phase pro-
2
3
3
duced by reaction of NiCl with LiAlH would be controlled by
Supporting Information for this article is available on the WWW under
http://dx.doi.org/10.1002/cctc.201402957.
2
4
[15,16]
stoichiometry, as proposed in Equation (1).
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1
,3,5 Me3C6H3
-
NiCl þ LiAlH4 ƒƒƒƒƒƒ! NiAl þ AlCl þ LiCl þ H
ð1Þ
To probe the formation and phase transition of Ni–Al IMCs
during the annealing process, the effect of temperature was
further investigated. As shown in Figure S2, only metallic Ni
and Al are formed upon annealing at 5508C. However, as the
temperature is increased to 6508C, characteristic diffraction
peaks at 2q=44.3, 30.9, 64.5, and 81.68 attributable to NiAl
with a cubic structure are observed. If the temperature is
raised to 7508C, the peaks for NiAl become sharper and peaks
for Al O start to appear; consequently, 6508C is a key temper-
ature for crystal transformation. The improved temperature
promotes aggregation of the Ni–Al IMC nanoparticles with en-
hanced crystallinity. All the synthetic results are summarized in
the simplified scheme of the reaction pathways (some inter-
mediates and byproducts are omitted) in Figure 1b.
2
ꢀ
64 C
x
3
2
1
In this work, the molar ratio of NiCl and LiAlH was con-
2
4
trolled at 4:3, 4:5, 4:7, and 4:9. The microstructures of the as-
prepared samples were determined by X-ray diffraction (XRD;
see Figure S1, Supporting Information). NiCl , metal Al, and
2
produced LiCl·H O were detected, but metallic Ni and Ni–Al
2
IMCs were missing. It is presumed that the intermetallic phases
did not directly form during the solvent step and that further
annealing was required to transform the as-precipitated pow-
ders yielded in the solvent step to drive the reactions to com-
pletion.
2
3
The XRD patterns of the samples annealed at 6508C under
an atmosphere of Ar are shown in Figure 1a. Typical diffraction
peaks at 2q=44.5, 51.8, and 76.48 can be detected in the
NiAl3/4 sample, and these peaks correspond to cubic-phase
The composition and physicochemical properties of the as-
prepared Ni–Al IMC catalysts are listed in Table 1. The actual
Table 1. Composition and physicochemical properties of the Ni–Al IMC
catalysts.
Sample
Crystalline phases
Actual Ni/Al molar ratio
Surface area
2
ꢁ1
[
m g ]
NiAl3/4
NiAl5/4
NiAl7/4
NiAl9/4
Ni, NiCl
NiAl, Ni
NiAl
2
4:1.6
4:3.1
4:5.7
4:8
25
15
15
14
3
Al
Al
NiAl, Ni
2
3
compositions are similar to the nominal compositions. Howev-
er, the actual Ni/Al ratios are bigger than the nominal value,
which indicates that a small quantity of Al as the byproduct
(
AlCl ) is removed during the chemical route. In combination
3
Figure 1. a) XRD patterns of Ni–Al IMCs with different molar ratios annealed
at 6508C. b) Simplified schematic representation of the reaction pathways.
with analysis of the XRD patterns of the as-prepared Ni–Al
IMCs, Al mostly reacts with Ni to form Ni–Al IMCs, but a small
amount of Al exists as amorphous Al O . The BET surface areas
2
3
nickel (JCPDS No. 04-0850). At the same time, trace amounts
of NiAl3/4, NiAl5/4, NiAl , and NiAl
are 25, 15, 15, and
9/4
7/4
2
ꢁ1
of NiCl were residual, which indicates that superfluous LiAlH4
14 m g , respectively (Table 1). Because an increase in the
2
is needed to promote the formation of Ni–Al IMCs. By increas-
amount of reducing agent (i.e., LiAlH ) used produces a violent
4
ing the content of the Al source (LiAlH ), the diffraction peaks
reaction during the formation of the Ni–Al IMCs in the route,
the Ni–Al IMC particles aggregate, which leads to collapse of
4
at 2q=43.9, 50.7, and 75.38 attributable to the (112), (004),
[17]
and (220) reflections of tetragonal-phase Ni Al (JCPDS No. 50-
the pore structure and a decrease in the surface areas. In ad-
3
1265), respectively, are observed in the XRD pattern of the
dition, the N adsorption/desorption processes on the Ni–Al
2
NiAl5/4 sample. In addition, the sample shows typical diffraction
peaks at 2q=44.3, 30.9, 64.5, and 81.68, which indicates the
formation of NiAl (cubic, JCPDS No. 44-1188). Upon decreasing
the Ni/Al molar ratio to 4:7, the diffraction peaks of NiAl
IMCs show incomplete type II isotherms with type H3 hystere-
sis loops, and this can be attributed to well-developed uniform
mesoporous structures resulting from the stacking of sheet
particles (as shown in Figure S3).
become sharper, whereas the peaks of Ni Al disappear. A fur-
The SEM image and mappings of the NiAl7/4 sample and the
corresponding energy-dispersive X-ray spectroscopy (EDX)
spectrum are presented in Figure 2. Clearly, the NiAl7/4 particles
have aggregated into an irregularly shaped sub-micrometer-
sized microstructure with sintered, rounded 50–100 nm parti-
cles; this indicates that the temperature near or above the
melting point of the Ni–Al IMCs (>12008C) may be reached in
the exothermic reaction stage. Figure 2 depicts the EDX spec-
trum of the nanoparticles and gives quantitative information
on their chemical composition, which confirms the existence
of Ni and Al elements with a Ni/Al ratio of 1:1.36 in the
3
ther decrease in the Ni/Al molar ratio to 4:9 results in three
new diffraction peaks at 2q=18.1, 25.3, and 31.28, which can
be assigned to hexagonal-phase Ni Al (JCPDS No. 14-0648). In
2
3
addition, the LiCl byproduct sublimes after thermal treating.
Mixtures of the desired intermetallic phases are obtained,
whereas NiCl and metal Al are eliminated; this indicates that
2
a reaction occurs between nanocrystalline Al and Ni. The for-
mation of Ni–Al IMCs involves the following sequence as
a function of the content of the Al source (LiAlH ): Ni(cubic)!
4
Ni Al(tetragonal)!NiAl(cubic)!Ni Al (hexagonal).
3
2
3
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Figure 2. SEM image and mappings of the NiAl7/4 IMC catalyst and the corre-
sponding energy-dispersive X-ray spectrum. Scale bar=30 mm.
sample. The result is consistent with the XRD analysis data and
further confirms the formation of NiAl. Homogeneous Ni and
Al distributions are found in the NiAl7/4 sample, as seen in the
corresponding elemental maps; this indicates that the Al
atoms are uniformly doped into the lattice of metallic Ni.
To investigate the structure and composition in the materi-
als, TEM and high-resolution (HR) TEM were performed. Fig-
ure 3a shows the HRTEM image of the NiAl5/4 sample. The
measured d value is approximately 0.2017 nm, and this can be
Figure 3. Representative low- and high-resolution TEM images of the Ni–Al
IMC samples with different Ni/Al molar ratios: a,b) 4:5, c,d) 4:7, and e,f) 4:9.
identified as the (112) plane of the Ni Al phase (d=
3
0.2062 nm). The crystalline phase was revealed as tetragonal
Ni Al by fast Fourier transform (FFT; Figure 3a, inset). In addi-
3
tion, the d spacing for the (004) plane of the Ni Al nanoparti-
3
cles was measured from such images and was found to be
0
0
.1786 nm, which is in close agreement with the bulk value of
.1798 nm (as shown in Figure 3b). Upon changing the Ni/Al
molar ratio to 4:7, the as-prepared NiAl7/4 sample presents
a nanosheet structure (as shown in Figure 3c), which is proba-
bly due to the formation of amorphous Al O . The HRTEM
2
3
image of NiAl7/4 reveals its crystalline nature, with a lattice
spacing of 0.2885 nm (Figure 3d), which can be indexed to the
(100) crystalline plane of the cubic phase of NiAl. A further in-
crease in the amount of Al to a Ni/Al molar ratio of 4:9 results
in NiAl9/4 that is both uniformly dispersed and weakly aggre-
gated (Figure 3e). The particle size is approximately 20 nm,
which is close to the value obtained from Scherrer’s equation.
In addition, an alumina matrix also exists in the sample, which
can be attributed to the excess amount of the Al source that
was used in the chemical synthesis process. Figure 3 f shows
the HRTEM image of the NiAl9/4 sample. The d value measured
from the image is 0.2016 nm, which is readily identified as hex-
agonal Ni Al [d=0.2010 nm, (102) plane]. Three types of Ni–
Figure 4. XPS of a) the Ni2p region and b) the Al2p region of the Ni–Al IMC
samples.
the Ni2p and Al2p regions for the Ni–Al IMCs catalysts. The
binding energy of the Ni2p3/2 core level for NiAl3/4 (Figure 4a)
2
3
[18]
Al IMCs (Ni Al, NiAl, and Ni Al ) can be obtained by changing
is 852.6 eV, which coincides well with that of pure Ni metal.
3
2
3
the Ni/Al ratio in the synthetic route.
The chemical shifts of NiAl7/4 and NiAl9/4 in relation to metallic
Ni are 0.5 and 0.8 eV, respectively. With an increase in the Al
concentration in the Ni–Al IMCs, the Ni2p3/2 core level shifts to
a positive level and the half-width decreases. In addition, the
To investigate the catalytic active sites and surface-chemis-
try–structure relationships, the surfaces of the Ni–Al IMC cata-
lysts were examined by XPS. Figure 4 shows the XPS spectra in
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asymmetry of the peak shape of Ni2p3/2 reduces. The peak at
58.5 eV attributable to satellite peak associates with the
Ni2p3/2 core level of NiAl3/4, and this can be attributed to the
alysts, the NiAl7/4 catalyst with the NiAl major phase showed
the highest conversion. Combined with the phase-state analy-
sis results obtained by XRD and TEM, it can be ascertained that
the catalytic activity of NiAl is much higher than that of pure
metallic Ni and that of the other Ni–Al IMCs (Ni Al and Ni Al ).
8
[
19]
many-body effect in the photoemission process. The positive
shift in the satellite peak increases as the Al concentration in
the Ni–Al IMCs increases. This result is similar to that of Pd in
3
2
3
The results can be well understood through a combination of
site isolation and the alteration of the electronic structure by
[
20]
Pd–Ga IMCs. Given that the transition-metal atoms are isolat-
ed by the main group elements in the IMCs, the electronic
[23,24]
chemical bonding.
The selectivity of the products shows
[21]
structure around the Fermi energy becomes altered.
Un-
that naphthalene hydrogenation to tetralin is the main reac-
tion (100% selectivity to tetralin at a contact time lower than
1.87 h). Decalin as a final product is only detected in a very
small amount at a high contact time (3.11 h), and the main
product is tetralin with a selectivity of 98% over the NiAl7/4 cat-
alyst, which indicates that the hydrogenation of tetralin is
a rate-controlled step over the Ni–Al IMCs. This phenomenon
is similar to naphthalene hydrogenation over carbides and sili-
fortunately, owing to the high concentration of Al O on the
2
3
surface, there is an extra broad peak at 73.5–76.5 eV in the
Al2p spectrum that corresponds to AlꢁO (as shown in Fig-
ure 4b), and this protects the samples from violent oxidation
[
22]
upon their exposure to air.
The catalytic hydrogenation of naphthalene over Ni–Al IMCs
catalysts was performed in a continuous fixed-bed reactor. The
hydrogenation of naphthalene occurs in two steps (Scheme 1):
[25,26]
cides.
Product selectivity of the hydrogenation of naphtha-
lene versus the contact time over the NiAl7/4 catalyst (as shown
in Figure S4) further confirms these semihydrogenation proper-
ties. Comparing the Ni–Al IMCs catalysts with conventional
naphthalene hydrogenation catalysts, even though the activity
[3]
of the Ni–Al IMCs was lower than that of NiO/SiO -Al O , the
2
2
3
Scheme 1. Hydrogenation of naphthalene.
selectivity to tetralin and stability were greatly enhanced.
To correlate the different activities among the Ni–Al IMCs,
the apparent rate constant of naphthalene hydrogenation was
calculated. Assuming pseudo-first-order kinetics for the hydro-
naphthalene is first converted into tetralin, and this is followed
by the formation of decalin. As shown in Figure 5, the conver-
sion of naphthalene over Ni–Al IMCs increases with an increase
in contact time. Typically, naphthalene conversion reaches
ꢁ1
genation of naphthalene, the rate constant k [h ] was calcu-
a
lated at a low conversion on the basis of the first-order-reac-
tion rate equation [Eq. (2)]:
11.3% over the NiAl7/4 catalyst at a low contact time (0.44 h)
and 54.6% at a high contact time (3.11 h). Among the four cat-
ꢁlnð1ꢁx
a
Þ ¼ k
a
t
ð2Þ
2
Figure 5. a) Conversion of naphthalene and b) selectivity to tetralin versus the contact time at 4.0 MPa H and 3408C over Ni–Al IMCs catalysts. c) Fitting of
the pseudo-first-ordered kinetic model to the experimental data for the hydrogenation of naphthalene. d) Hydrogenation of naphthalene as a function of
time on the NiAl7/4 IMC catalyst.
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in which x is the substrate consumption rate and t is the con-
a
tact time.
As shown in Figure 5c, the substrate consumption rate
[
ꢁln(1ꢁx )] is linearly related to the contact time (t), and con-
a
sequently, naphthalene hydrogenation over Ni–Al IMCs cata-
lysts is a pseudo-first-order reaction. The rate constant for the
NiAl3/4, NiAl5/4, NiAl7/4, and NiAl9/4 catalysts is 0.04, 0.18, 0.26,
ꢁ
1
and 0.14 h , respectively (Table 2). This result further confirms
that the catalytic activity of NiAl is superior to that of the Ni Al
3
a
Table 2. Pseudo-first-order rate constants k , activities, and selectivity of
the Ni–Al IMCs for the hydrogenation of naphthalene tested at 3408C
with a H
Catalyst
2
pressure of 4 MPa and a contact time of 1.18 h.
K
a
Conversion
[mol%]
Consumption rate of
naphthalene [nmolg s ]
Selectivity
[mol%]
ꢁ1
ꢁ1 ꢁ1
[
h
]
NiAl3/4
NiAl5/4
NiAl7/4
NiAl9/4
0.04
0.18
0.26
0.14
3.9
15.3
26.2
15.3
71.9
283.2
486.8
284.0
100
100
99.9
100
and Ni Al IMCs and to that of metallic Ni. The naphthalene
2
3
consumption rate also presents a similar relationship for the
four catalysts in the hydrogenation of naphthalene. In addition,
the selectivity to tetralin over the Ni–Al IMCs catalysts is
almost close to 100%. Armbrꢀster et al. observed that the
Figure 6. a) XRD patterns for the fresh and spent NiAl7/4 IMC catalyst (after
125 h) in the hydrogenation of naphthalene. b) Thermogravimetry (TG)
structural situations of Al Fe and Al Co resemble that of Ga-
13
4
13
4
curve of the spent NiAl7/4 IMC catalyst used to test carbon deposition.
[
12, 13]
only coordinated Pd atoms in the GaPd IMC,
which has
been proven to be an excellent semihydrogenation catalyst.
Therefore, the efficient and highly selective hydrogenation per-
formance of Ni–Al IMCs can be attributed to the special geom-
etry and electronic structure resulting from covalent interac-
tions between the Ni and Al atoms.
peak in the high-temperature region (110–8508C); consequent-
ly, carbon species are not formed on the catalysts during the
hydrogenation of naphthalene. Ni atoms are scattered and
spatially isolated by aluminum, which is similar to Ga-modified
To test the stability of the catalyst, the time course of naph-
thalene hydrogenation activity was observed for 125 h on the
[29,30]
Pd-based IMC surfaces.
This in turn resists carbon deposi-
NiAl7/4 IMC catalyst at 3608C, under H pressure of 4 MPa, with
tion. The results show that Ni–Al IMCs are promising catalysts
for semihydrogenation, which can be of high importance in
fine-chemical synthesis industries.
2
a contact time of 0.44 h. In Figure 5d, it is revealed that the
ꢁ
1
ꢁ1
naphthalene consumption rate was initially 295 nmolg
s
at
ꢁ
1
ꢁ1
5
h and it then increased to 325 nmolg s
at 20 h. Excitingly,
NiAl7/4 showed high stability and very high tetralin selectivity
of 100% up to 125 h. A similar result was observed on Pd–Ga
Conclusions
[27]
IMC catalysts used in alkyne-selective hydrogenation.
The
In summary, Ni–Al intermetallic compound catalysts with differ-
ent phases were examined for the selective hydrogenation of
naphthalene to tetralin. It was found that NiAl is a highly
active and selective catalyst with long-term stability. The cata-
lyst is highly resistant to coking and remains active for pro-
longed reaction times, which confirms that intermetallic com-
pounds can be broadly applied in heterogeneous catalysis.
effect of Ni–Al IMCs on the structure stability was determined
from measurements of phase state and carbon content in the
spent catalyst by using XRD and thermogravimetry, respective-
ly, as shown in Figure 6. The XRD patterns show that the struc-
ture of NiAl is almost invariant after the stability test, whereas
a new phase of Ni Al appears with reference to the standard
3
tetragonal-phase Ni Al (JCPDS No. 09-0097); consequently, part
3
of NiAl is reduced to Ni Al under reaction conditions that, to
3
[
28]
some extent, follow the reaction 3NiAl+3H !Ni Al+2AlH .
Experimental Section
2
3
3
In addition, the thermogravimetry curve of the spent NiAl7/4
IMC catalyst shows that only 5% of mass was lost from 60 to
The Ni–Al IMCs were prepared by a chemical synthesis route. Typi-
cally, a mixture of anhydrous NiCl (1.056 g, 8.15 mmol) and LiAlH
2
4
110 8C, and this can be attributed to removal of surface physi-
(0.541 g, 14.26 mmol) in 1,3,5-trimethylbenzene (30 mL) was
sorbed reaction substrates. However, there is no mass loss
heated at reflux at 1648C for 12 h. The resulting gray-black precipi-
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tate was collected after removing the solvent by centrifugation,
and the solid was dried under high vacuum at 708C. To synthesize
the nickel aluminide with various phases, the molar ratio of NiCl2
Keywords: aluminum
compounds · nickel · wet chemistry
·
hydrogenation
·
intermetallic
and LiAlH was controlled at 4:3, 4:5, 4:7, and 4:9. A 0.50 g portion
of the as-precipitated black solid was loaded into a tubular furnace
and calcined at 6508C for 3 h under an atmosphere of Ar. The ob-
4
[
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D/Max-RB diffractometer with a CuKa monochromated radiation
source. Elemental analyses of the catalysts, including the metal Ni
or Al, were detected by inductively coupled plasma atomic emis-
sion spectroscopy (ICP-AES). Nitrogen adsorption and desorption
isotherms were measured by using an Autosorb IQ surface-area
and pore-size analyzer. The morphology and structures of the as-
prepared products were analyzed by using high-resolution field-
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Supporting Information.
[
The catalytic activities of the Ni–Al IMCs catalysts were tested for
034803–034821.
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2
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2
[
[
[
[
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ꢁ1
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Wcat
nfeed
t ¼
ð3Þ
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[
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We gratefully acknowledge financial support provided by the Na-
tional Natural Science Foundation of China (21373038 and
[
21403026), the China Postdoctoral Science Foundation
(
2014M551068), and the Fundamental Research Funds for the
Received: November 28, 2014
Revised: January 4, 2015
Published online on && &&, 0000
Central Universities (DUT14RC(3)007). We thank Dr. Alex C. W.
Tsang for improving the English in this paper.
&
ChemCatChem 0000, 00, 0 – 0
www.chemcatchem.org
6
ꢁ 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

FULL PAPERS
Selecting the best: Ni–Al intermetallic
compounds (IMCs) are successfully pre-
pared by a chemical synthesis route.
These compounds present good activity,
high selectivity, and long-term stability
in the semihydrogenation of naphtha-
lene to tetralin owing to alteration of
the electronic structure by chemical
bonding.
X. Chen, Y. Ma, L. Wang, Z. Yang, S. Jin,
L. Zhang, C. Liang*
&& – &&
Nickel–Aluminum Intermetallic
Compounds as Highly Selective and
Stable Catalysts for the
Hydrogenation of Naphthalene to
Tetralin
ChemCatChem 0000, 00, 0 – 0
www.chemcatchem.org
7
ꢁ 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ