A non-noble amorphous Co-Fe-B catalyst highly selective in liquid phase hydrogenation of crotonaldehyde to crotyl alcohol

Article abstract of DOI:10.1039/b505701a

A nanosized amorphous Co-Fe-B catalyst exhibited higher selectivity and yield to crotyl alcohol than noble Pt-based catalysts in the hydrogenation of crotonaldehyde and could be prepared by a facile chemical reduction method. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2005.

Full text of DOI:10.1039/b505701a

View Article Online / Journal Homepage / Table of Contents for this issue
L E T T E R
A non-noble amorphous Co–Fe–B catalyst highly selective in liquid
phase hydrogenation of crotonaldehyde to crotyl alcohol
Yan Pei, Jianqiang Wang, Qiang Fu, Pingjun Guo, Minghua Qiao,* Shirun Yan and
Kangnian Fan*
Department of Chemistry and Laboratory of Molecular Catalysis and Innovative Materials,
Fudan University, Shanghai 200433, P. R. China. E-mail: mhqiao@fudan.edu.cn.
E-mail: knfan@fudan.edu.cn; Fax: þ86-21-65642978; Tel: þ86-21-65643977
Received (in Montpellier, France) 26th April 2005, Accepted 24th May 2005
First published as an Advance Article on the web 16th June 2005
A nanosized amorphous Co–Fe–B catalyst exhibited higher se-
lectivity and yield to crotyl alcohol than noble Pt-based cata-
lysts in the hydrogenation of crotonaldehyde and could be
prepared by a facile chemical reduction method.
(TEM, JEOL JEM2011) in Fig. 1 reveal the average particle
size of 16 and 9 nm for Co–B and Co–Fe–B catalysts,
respectively, with the latter bearing a much narrower particle
size distribution than the former. The selected-area electron
diffraction patterns (SAED, insets in Fig. 1) present only
diffractive halos rather than distinct dots, consistent with the
long-range disordering but short-range ordering structure
characteristic of amorphous alloys.15
The selective hydrogenation of a,b-unsaturated aldehydes to
their corresponding unsaturated alcohols is among one of the
most important reactions in the preparation of various fine
chemicals such as fragrances, agrochemicals and pharmaceu-
ticals.1,2 However, the manipulation of selectivity in the hydro-
genation of a,b-unsaturated aldehydes is a considerable
challenge, since the production of saturated aldehyde or satu-
rated alcohol is thermodynamically more favorable than that
of unsaturated alcohol. Therefore, great efforts have been
Fig. 2 compares the X-ray photoelectron spectra (XPS,
Perkin Elmer PHI5000C) of Co 2p, B 1s and Fe 2p core levels
for the Co–B and Co–Fe–B catalysts. It can be concluded on a
qualitative basis that the incorporation of iron increased the
amount of oxidized Co (Co21 16 and B (B31 17
) species on the
)
surface in a way which is unclear for the time being. For the
Co–Fe–B catalyst, iron exists in both the metallic and oxidized
states, with the Fe 2p3/2 binding energies (BEs) at B707.1 and
709.8 eV, respectively.17 It is worth noting that the B 1s BE of
elemental B in these amorphous catalysts is B188.2 eV, about
1.2 eV higher than that of pure boron powder. For metal-rich
borides such as NiB, Ni2B, CoB, Co2B and FeB, based on
magnetic susceptibility, 59Co NMR and high resolution brems-
strahlung isochromat measurements, it is suggested that B
donates electrons to the metal.18 The BE shift of B in the
present case can be interpreted in a similar manner.
devoted to enhancing the catalytic activity towards the C
O
Q
group, while simultaneously suppressing the activity towards
the C C double bonds of a,b-unsaturated aldehydes.
Q
In principle, the selectivity for a desired unsaturated alcohol
is determined by the relative accessibility and the binding
strength of the C C and the C O bonds to the catalyst.2,3
Q
Q
In this sense, a properly designed catalyst with more suitable
surface sites, which invoke the polarization of the C O bond
Q
or inhibit the adsorption of a,b-unsaturated aldehydes in the
C
C bonding configuration, can lead to high selectivity in the
The liquid phase hydrogenation of crotonaldehyde (CRAL)
over nanosized amorphous Co–B and Co–Fe–B catalysts
results in crotyl alcohol (CROL), butanal (BUAL), butanol
(BUOL), and diacetal (1,1-diethoxybutane, DA) from the side
reaction between BUAL and ethanol used as solvent (Scheme
1). Table 1 summarizes the initial selectivity for CROL and
product distribution corresponding to the maximum yield of
CROL with Co–B and Co–Fe–B catalysts. It turns out that
iron has a remarkable positive effect on the selectivity in CRAL
hydrogenation. With the Co–B catalyst, BUAL is the preferred
product, while the initial selectivity for CROL is only about
23.4%, with the maximum yield of CROL being 18.0 mol%. In
contrast, over the Co–Fe–B catalyst, the initial selectivity for
CROL amounts to 71.0%, and the maximum yield of CROL
reaches as high as 63.5 mol%. It is worth emphasizing here
that, although some elaborately designed Pt-based catalysts
can give rise to a higher selectivity for CROL (470%),7,9,11 the
value is only achievable at low conversion and a yield compar-
able to the present case has never been reported to the best of
our knowledge. More recently, on a highly loaded Co–SiO2
catalyst prepared by Djerboua et al.,19 the extrapolated CROL
selectivity at zero CRAL conversion exceeds 90%. However,
the selectivity decreases linearly to 77% at CRAL conversion
of 55%, still resulting in a CROL yield inferior to the present
case.
Q
hydrogenation of a,b-unsaturated aldehydes. In a generalized
context of feasible ways to modify the active sites of a catalyst,
the addition of a second, more electropositive metal4–7 or the
use of oxide supports,8–11 is efficient in promoting the catalytic
performance. The presence of electronic effects has been pro-
posed to be responsible for the improved selectivity.
In this paper, an attempt has been made to develop the
nanosized amorphous Co–Fe–B catalyst based on a facile
chemical reduction method, as amorphous Co–B catalysts
have been found moderately selective in the hydrogenation of
a,b-unsaturated aldehydes to unsaturated alcohols.12–14 We
identified that over a Co–Fe–B catalyst with a specific for-
mulation, the high selectivity for crotyl alcohol is retained even
at high crotonaldehyde conversion, thus leading to a crotyl
alcohol yield of 63.5 mol%, which is much higher than those
reported for Pt-based catalysts, within our knowledge.
The bulk composition of the as-prepared Co–Fe–B catalyst
was determined to be Co30.8Fe37.1B32.1, in atomic ratios, by
chemical analysis (ICP-AES, IRIS Intrepid), with the Co : Fe
ratio somewhat higher than the nominal ratio used in the
preparation. It was found that the introduction of iron dras-
tically increased the specific surface area, the surface area of the
Co–Fe–B catalyst being 35 m2 gꢀ1, about twofold that of Co–B
catalyst. Accordingly, the transmission electron micrographs
T h i s j o u r n a l i s & T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 5
992
N e w J . C h e m . , 2 0 0 5 , 2 9 , 9 9 2 – 9 9 4

View Article Online
Scheme 1 Crotonaldehyde hydrogenation network.
Based on a systematic theoretical calculation, Delbecq and
Sautet suggested that the main attractive action in adsorbing
aldehyde on surfaces via the C O bond is the back-donation
Q
from the metal orbitals into the p*CO orbital. Either the shift-
down of the p*CO orbital or the shift-up of the metal orbitals
facilitates a better interaction and stronger adsorption, which is
crucial for an improved selectivity for the unsaturated alco-
hol.20 In the present case, XPS revealed that there are sub-
stantial amounts of oxides of iron, cobalt and boron on the
Co–Fe–B catalyst. Although the presence of surface oxides is
adverse to the activity of the catalyst by blocking the active
sites, they can function as Lewis acid sites and lower the pC* O
orbital by complexation with the C O group. On the other
Q
hand, donation of electrons from elemental B is anticipated to
shift the orbitals of metallic Co up. Meanwhile, the increased
electron density on metallic Co in the Co–Fe–B catalyst
relative to elemental Co without any electronic interaction
Fig. 1 The TEM images and particle size distributions of (a) Co–B
and (b) Co–Fe–B catalysts. Insets are the corresponding SAED
patterns.
with B, can weaken the binding of the C C group on the
active sites.20 The synergic effect between the surface oxides
and the electron-rich metallic Co can account for the smaller
Q
decrease in the hydrogenation activity of the C O group
Q
relative to the C C group. It is worth mentioning here that
Q
the present method is also applicable in the selective hydro-
genation of cinnamylaldehyde to cinnamyl alcohol. Over an-
other amorphous Co–Fe–B catalyst with a formulation
somewhat different from the present one, a cinnamyl alcohol
yield of 495% was obtained.
In summary, over the nanosized amorphous Co–Fe–B cat-
alyst, higher selectivity and yield of crotyl alcohol can be
achieved in the hydrogenation of crotonaldehyde. The unique
electronic structure of the amorphous metal boride catalyst and
the existence of more surface oxides evoked by iron incorpora-
tion, facilitate the activation of the C O bond relative to the
C
Q
C bond, thus rendering an excellent selectivity towards
Q
crotyl alcohol over the non-noble Co–Fe–B catalyst.
Fig. 2 The XPS spectra of Co 2p, B 1s and Fe 2p levels of the
nanosized amorphous Co–B and Co–Fe–B catalysts.
Experimental
In a control experiment, no hydrogenation products were
detectable using a similarly prepared amorphous Fe–B cata-
lyst, implying that iron itself is not active and selective at all in
the title reaction. Further analysis of the initial formation rates
of CROL (rCQO) and BUAL (rCQC) over Co–B and Co–Fe–B
catalysts revealed that the improved selectivity for CROL after
iron addition is not caused by enhancing the reactivity of the
The nanosized amorphous Co–Fe–B catalyst was prepared as
follows. 12.7 ml of an aqueous solution of KBH4 (2.0 M) was
added, in a flow rate of 1.5 ml minꢀ1, to 17.0 ml of an aqueous
solution containing 3.4 mmol CoCl2 and 5.1 mmol FeCl3 at
293 K. Gentle stirring was maintained throughout the reduc-
tion. When no hydrogen bubbles were released, the resulting
black precipitate was centrifuged and washed with distilled
water to neutrality, then with ethanol three times to replace
water. The catalyst was stored in ethanol for activity tests and
C
O group; rather, iron suppresses more the reactivity of the
C group than that of the C O group, thus reversing
Q
Q
C
Q
the rCQO : rCQ ratio from 0.33 : 1 to 2.5 : 1.
C
Table 1 Results of crotonaldehyde hydrogenation over Co–B and Co–Fe–B catalysts
Selectivitya (mol%)
Conversiona
(%)
YCROL
(mol%)
Sb
(mol%)
rCQ
rCQ
C
a
b
b
O
ꢀ1
ꢀ1
)
CROL
BUAL
BUOL
DA
Catalyst
(mmol minꢀ1 gcat
)
(mmol minꢀ1 gcat
Co–B
Co–Fe–B
89.3
94.7
20.2
67.1
41.7
26.3
38.1
4.3
0
2.3
18.0
63.5
23.4
71.0
0.29
0.069
0.89
0.028
a
b
Values corresponding to the maximum yield of crotyl alcohol. Initial selectivity to crotyl alcohol (S), and the initial formation rates of crotyl
alcohol (rCQO) and butanal (rCQC).
N e w J . C h e m . , 2 0 0 5 , 2 9 , 9 9 2 – 9 9 4
993

View Article Online
characterization. For comparison, Co–B and Fe–B catalysts
were prepared in a way similar to that of the Co–Fe–B catalyst.
Crotonaldehyde (97%) was further purified by distillation
before activity tests. 0.50 g of catalyst, 45 ml of ethanol and
5.0 ml of crotonaldehyde were transferred into a 220 ml
stainless steel autoclave. The hydrogenation was performed
at 373 K, 1.0 MPa of H2, and a stirring rate of 1000 rpm to
exclude diffusion effects. The reaction products were analyzed
by a GC122 gas chromatograph equipped with a flame ioniza-
tion detector (FID) and a 30 m PEG-20M capillary column.
5
6
7
P. Beccat, J. C. Bertolini, Y. Gauthier, J. Massardier and P. Ruiz,
J. Catal., 1990, 126, 451.
F. Coloma, A. Sepu
Rodrıguez-Reinoso, Appl. Catal., A, 1996, 148, 63.
J. L. Margitfalvi, Gy. Vanko, I. Borbath, A. Tompos and A.
Vertes, J. Catal., 2000, 190, 474.
´ lveda-Escribano, J. L. G. Fierro and F.
´
´
´
´
8
9
A. Dandekar and M. A. Vannice, J. Catal., 1999, 183, 344.
M. Consonni, D. Jokic, D. Yu Murzin and R. Touroude,
J. Catal., 1999, 188, 165.
10 R. Zanella, C. Louis, S. Giorgio and R. Touroude, J. Catal., 2004,
223, 328.
11 P. Concepcion, A. Corma, J. Silvestre-Albero, V. Franco and
´
J. Y. Chane-Ching, J. Am. Chem. Soc., 2004, 126, 5523.
12 Y. Z. Chen and K. J. Wu, Appl. Catal., 1991, 78, 185.
13 Y. Z. Chen, S. W. Wei and K. J. Wu, Appl. Catal., A, 1993, 99, 85.
14 Y. Pei, H. R. Hu, J. Fang, M. H. Qiao, W. L. Dai, K. N. Fan and
Acknowledgements
This work was supported by the State Key Basic Research
Development Program (G2000048009), the NSFC (20203004)
and Shanghai Science and Technology Committee
(03QB14004).
H. X. Li, J. Mol. Catal. A: Chem., 2004, 211, 243.
´
15 A. Molna
´
r, G. V. Smith and M. Barto
´
k, Adv. Catal., 1989, 36
329.
16 F. B. Noronha, M. Schmal, B. Moraweck, P. Delichere, M. Brun,
F. Villain and R. Frety, J. Phys. Chem. B, 2000, 104, 5478.
´
References
17 J. F. Moulder, W. F. Stickle, P. E. Sobol and K. D. Bomben,
Handbook of X-ray Photoelectron Spectroscopy, ed. J. Chastain,
Perkin-Elmer Corporation, USA, 1992.
18 Y. Okamoto, Y. Nitta, T. Imanaka and S. Teranishi, J. Chem.
Soc., Faraday Trans. 1, 1979, 15, 2027.
19 F. Djerboua, D. Benachour and R. Touroude, Appl. Catal., A,
2005, 282, 123.
20 F. Delbecq and P. Sautet, J. Catal., 1995, 152, 217.
´
´
M. Bartok and A. Molna
1
´
r, in Supplement A3: The Chemistry of
Double-Bonded Functional Groups, ed. S. Patai, Wiley, New York,
1997, ch. 16, p. 843.
P. Gallezot and D. Richard, Catal. Rev. Sci. Eng., 1998, 40, 81.
2
3
4
V. Pone
T. B. L. W. Marinelli, S. Nabuurs and V. Pone
151, 431.
´
c, Appl. Catal., A, 1997, 149, 27.
´
c, J. Catal., 1995,
994
N e w J . C h e m . , 2 0 0 5 , 2 9 , 9 9 2 – 9 9 4