Hydrogenation of aromatic aldehydes to aromatic hydrocarbons over Cu-HZSM-5 catalyst

Article abstract of DOI:10.1016/j.catcom.2014.07.038

With benzaldehyde as a model compound, the hydrogenation of aromatic aldehydes to aromatic hydrocarbons was investigated. Cu-HZSM-5 exhibited excellent catalytic performance for the reaction. The obtained catalysts were characterized by N₂ adsorption/desorption, N₂O chemisorptions, X-ray diffraction, NH₃-temperature programmed desorption and X-ray photoelectron spectroscopy. It was found that Cu ⁰ active species exhibited poor activity for the hydrogenation of benzene ring, while the strong acidity of HZSM-5 accelerated the hydrogenation reaction via hydrogen spillover phenomenon and the C-O activation effect. In addition, the catalyst was proved to be effective for the hydrogenation of a series of aromatic aldehydes to corresponding aromatic hydrocarbons.

Full text of DOI:10.1016/j.catcom.2014.07.038

Catalysis Communications 57 (2014) 45–49
Contents lists available at ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short Communication
Hydrogenation of aromatic aldehydes to aromatic hydrocarbons over
Cu-HZSM-5 catalyst
b
Xiangjin Kong a, , Ligong Chen
⁎
a
Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell Technology, School of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng 252059, PR China
School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, PR China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 June 2014
Received in revised form 23 July 2014
Accepted 25 July 2014
Available online 4 August 2014
With benzaldehyde as a model compound, the hydrogenation of aromatic aldehydes to aromatic hydrocarbons
was investigated. Cu-HZSM-5 exhibited excellent catalytic performance for the reaction. The obtained catalysts
were characterized by N2 adsorption/desorption, N2O chemisorptions, X-ray diffraction, NH3-temperature
programmed desorption and X-ray photoelectron spectroscopy. It was found that Cu0 active species exhibited
poor activity for the hydrogenation of benzene ring, while the strong acidity of HZSM-5 accelerated the hydrogena-
tion reaction via hydrogen spillover phenomenon and the C–O activation effect. In addition, the catalyst was proved
to be effective for the hydrogenation of a series of aromatic aldehydes to corresponding aromatic hydrocarbons.
© 2014 Elsevier B.V. All rights reserved.
Keywords:
Benzaldehyde
Aromatic aldehydes
Cu-HZSM-5
1. Introduction
to corresponding aromatic hydrocarbons in a fixed-bed reactor. The
obtained catalyst was studied with some physical methods. In addition,
The reduction of carbonyls to corresponding methylenes was a
widely used reaction in fine chemical industries, pharmaceutical indus-
tries as well as the upgrading of biomass to fine chemicals or transport
fuel [1–3]. Nowadays, hydrogenation/deoxygenation was considered
to be an effective method to complete this kind of functional group
transformation [4–6]. During this reduction process, the carbonyl com-
pound was converted to alcohol through hydrogenation firstly, followed
by hydrogenolysis to obtain the corresponding compounds. However,
some of the carbonyl compounds cannot form the double bonds by
dehydration because they do not have the available hydrogen atoms
on adjacent carbon atoms, such as benzaldehyde. Therefore the direct
hydrogenolysis of carbon\oxygen bonds is needed. It is well known
that the hydrogenolysis of C\O bond is quite hard, and often required
noble catalysts [7–10]. However, the high cost of these catalysts
prohibits their scale-up for large-scale continuous processes. Recently,
several transition metal (Ni, Co, Cu) based catalysts have been used
for the hydrogenation/deoxygenation reaction [4,11–13]. Whereas, to
the best of our knowledge, most of the reported studies were focused
on the hydrogenation of phenols or other oxygen-containing com-
pounds to saturated hydrocarbons, and hydrogenation of aromatic alde-
hydes to corresponding aromatic hydrocarbons has seldom reported
[14–16].
stability and generality of this catalytic process were also investigated.
2. Experimental
2.1. Materials and catalysts
The used aromatic aldehydes were obtained from Tianjin Guangfu
Fine-chemical institute. The parent HZSM-5 powder with a nominal
Si/Al ratio of 25 was purchased from Nankai University catalyst Co.,
Ltd. Pseudo-boehmite was supplied by Jiangyan Chemical Auxiliary
Factory (Jiangyan, China). All the commercially available solvents and
reagents were used without further purification.
In the present studies, the metal species weight percent on the
catalyst is 20%. All catalysts used in this study were prepared by the
coprecipitation-kneading method. For example, Cu-HZSM-5 was pre-
pared as follows: a solution of Cu(NO3)2 · 3H2O (0.50 mol) in 800 mL
water and a solution of sodium carbonate (0.60 mol) in 800 mL water
were simultaneously added to a 5000 mL beaker with vigorous stirring
at room temperature. After the reaction mixture was aged for 1 h, the
precipitate was filtered and washed with water until the pH ≈ 7 and
then the precipitate was dried in air at 120 °C for 4 h. Then, the obtained
metal carbonates (38.8 g) were kneaded with a mixture of 56.0 g HZSM-5
and 36.1 g pseudo-boehmite (used as the binder for extrusion), followed
by molding to bars by an extruder. After drying in air at 110 °C for 6 h, the
catalysts were calcined at 500 °C for 4 h. The Cu based and Ni based
catalysts were reduced at 240 °C and 360 °C for 4 h respectively in a
stream of hydrogen under 1.0 MPa before use.
In the present studies, benzaldehyde was selected as a model com-
pound to evaluate a catalyst for the hydrogenation of aromatic aldehydes
⁎
Corresponding author.
E-mail address: kongxjin@163.com (X. Kong).
http://dx.doi.org/10.1016/j.catcom.2014.07.038
1566-7367/© 2014 Elsevier B.V. All rights reserved.

46
X. Kong, L. Chen / Catalysis Communications 57 (2014) 45–49
Table 2
N2 sorption characteristics of the samples.
Sample a SBET(m2/g) Vtotal b (cm3/g)
Ni-γ-Al2O3 195.3 0.53
Vmicropc (cm3/g)
Daverage (nm)
0.00
0.00
0.06
0.16
0.01
10.9
10.5
5.6
2.1
8.73
Cu-γ-Al2O3
Cu-HZSM-5
HZSM-5
182.5
241.6
367.8
234.6
0.48
0.34
0.20
0.51
γ-Al2O3
a
N2 sorption measurements were conducted on the oxide precursors.
Evaluated from N2 uptake at a relative N2 pressure of 0.99.
T-method micro pore volume.
b
c
Scheme 1. The reaction pathway for the hydrodeoxygenation of benzaldehyde.
3. Results and discussion
3.1. Catalyst modification
2.2. Catalyst characterization
In our previous studies [19], Ni-γ-Al2O3 were demonstrated to be
effective for the hydrogenation of benzaldehyde in the presence of
aniline, thus it is used for the reaction in the absence of aniline, firstly.
The obtained reaction mixture was identified by GC–MS, besides the
desired product toluene, methylcyclohexane and benzyl alcohol were
also detected. According to the above results, the reaction pathway
was deduced and shown in Scheme 1. Methylcyclohexane was reasonably
generated from the further hydrogenation of the benzene ring of toluene
or benzaldehyde. It is obvious that the formation of methylcyclohexane
is due to the poor selective hydrogenation ability of Ni-γ-Al2O3.
According to our previous studies [13], Cu based catalysts displayed
poor activity for the hydrogenation of benzene ring. So as to inhibit the
formation of methylcyclohexane, Cu-γ-Al2O3 was employed for the hy-
drogenation of benzaldehyde, the obtained results are listed in Table 1.
Over this catalyst, the formation of methylcyclohexane is successfully
inhibited, and the selectivity towards toluene sharply increased to
51.8%. Nevertheless, such a result is still under our expectations due to
the quite high amounts of benzyl alcohol in the reaction mixture. As de-
scribed in Scheme 1, toluene is formed through the hydrogenolysis of
benzyl alcohol. Since, the hydrogenation of benzaldehyde is not difficult,
we assumed that the quite poor selectivity of toluene is mainly due
to the weak C\O bond hydrogenolysis ability of Cu-γ-Al2O3. Thus,
even Cu-γ-Al2O3 was proved to be effective to inhibit the formation of
methylcyclohexane; it should be improved further in order to enhance
its hydrogenolysis ability. Recently, several studies have demonstrated
that the acid sites on the catalyst could facilitate the hydrogenation
process. Barbelli [20], Wu and others [21–23] reported that the strong
acidic sites on the catalyst were responsible for the hydrogenolysis
of C\O bond. It is well known that HZSM-5 has a strong acidity
than γ-Al2O3, thus it was employed as the support to improve the
performance of Cu based catalyst, and the obtained reaction results
are summarized in Table 1.
Textural properties of catalysts were measured by BET method using
a NOVA 2000e analyzer (Quantachrome, US). X-ray diffraction (XRD)
was carried out on a Rigaka D/max 2500 X-ray diffractometer with
Cu-Kα radiation (40 kV, 100 mA) in the range of 5–95°. The mean diam-
eter of Cu crystals was calculated from XRD patterns using Scherrer
equation. X-ray photoelectron spectroscopy (XPS) was carried out on
a PHI1600 spectrometer. To avoid the sample being exposed to air, all
the samples were sealed and transferred in a glove box before XPS
and XRD analysis. The dispersions of copper and exposed copper surface
areas were determined by N2O chemisorptions [17,18]. The loading of
Cu on the catalysts were identified by inductively coupled plasma
analysis (ICP) on a Varian 710-ES spectrometer. NH3-temperature pro-
grammed desorption (NH3-TPD) was performed with a TP-5000 instru-
ment with a thermal conductivity detector (TCD)
2.3. Catalytic test
The hydrogenation reaction was carried out in a fixed-bed reactor
with an inner diameter of 15 mm and a length of 660 mm, which was
loaded with 40.0 mL catalysts (cylinder catalyst particle with diameter
of 3 mm and height about 2–3 mm). Amounts of inert ceramic balls
were loaded over the catalyst layer in the reactor to avoid the bypass
and non-uniform flow. The solution of each aldehyde in 1,4-dioxane
(concentration of the aromatic aldehyde is 20.0 wt.%) was dosed into
the reactor by a pump, respectively. The catalytic reaction was conduct-
ed at temperature 120 °C, H2 pressure 2 MPa, GHSV 150 h−1 (pure H2),
LHSV 0.6 h−1. The reaction mixture was collected using cold trap
(0–2 °C). The GC–MS (Polaris Q, Thermo Finngan, America) was used
to confirm the components of the reaction mixture, which was equipped
with an ion trap MS detector. The composition of the reaction mixture
was determined by GC with an OV-1701 capillary column (30 m ×
0.25 mm, 0.2 μm film thickness). The mass balance of the experiment
Just as what we expected, the amount of benzyl alcohol over
Cu-HZSM-5 is sharply reduced, the selectivity of toluene remarkably
increased to 70.6%, and no methylcyclohexane was detected, which
indicated that the formation of methylcyclohexane was mainly depended
on the metal active sites on the catalyst. In addition, the conversion of
benzaldehyde was increased from 84.5% to 90.2%, this result demonstrat-
ed that the hydrogenation performance of the catalyst was also improved
by changing the support. Since, Cu-HZSM-5 exhibited an excellent perfor-
mance for the hydrogenation of benzaldehyde, the obtained catalysts are
investigated by some physical methods.
were around 96
2% for all reaction runs which were calculated by
the ratio of total carbons in outlet and inlet,
Table 1
The reaction results of benzaldehyde over Ni or Cu based catalysts.
Catalysts
Conversion (%) Selectivity (%)
Methyl
cyclohexane
Toluene Benzylalcohol Othera
Table 3
N2O chemisorptions characteristics of the samples.
Ni-γ-Al2O3
Cu-γ-Al2O3
Cu-HZSM-5 90.2
88.6
84.5
11.4
0.0
0.0
44.2
51.8
70.6
42.8
46.2
28.0
1.6
2.0
1.4
Sample a
Cu contenta (wt.%)
Dispersionb (%)
SCub (m2 g−1
)
Cu-γ-Al2O3
Cu-HZSM-5
19.6
19.8
4.4
4.7
6.0
6.3
Reaction conditions: temperature 120 °C, H2 pressure 2 MPa, GHSV 150 h−1 (pure H2),
LHSV 0.6 h−1
a
.
Measured by ICP–AES.
Determined by N2O chemisorptions.
a
b
Benzene and a very few of undetermined products.

X. Kong, L. Chen / Catalysis Communications 57 (2014) 45–49
47
x104
12
Atomic %
O1s 28.8
C1s 58.2
Al2p 9.1
Si2p 3.4
Cu2p 0.6
o
Cu
10
8
o
o
6
o
o
(b)
(a)
4
2
20
40
60
80
100
0
1000
800
600
400
200
0
2 Theta (deg)
Binding energy (eV)
Fig. 1. XRD patterns for (a) Cu-γ-Al2O3 and (b) Cu-HZSM-5.
Fig. 3. Full XPS spectra of the reduced Cu-HZSM-5.
The dispersions of copper and exposed copper surface areas on Cu
based catalysts were measured by N2O chemisorptions, and the obtain-
ed results are listed in Table 3. As the support changed from Al2O3 to
HZSM-5, the dispersions of copper increased from 4.4% to 5.1% and
the exposed copper surface areas (SCu) increased from 5.9 m2 g−1 to
6.8 m2 g−1
.
(c)
3.2.2. XRD
The XRD patterns of the reduced Ni-γ-Al2O3 (Fig. S1) implied
(b)
(a)
that Ni0 was the metal active center, which is in accordance with our
previous studies [19]. the XRD patterns of the reduced Cu-γ-Al2O3 and
Cu-HZSM-5 are depicted in Fig. 1. The typical diffraction lines at 43.3°,
50.4°, 74.2° and 90.0° in the XRD curves could be assigned to the crystals
of elementary copper. In addition, without obvious diffraction lines of
oxidized copper compounds were observed from Fig. 1. These results
indicated that the Cu species precursors were completely reduced
to Cu0 during the catalyst reduction process, and thus Cu0 could be
confirmed as the main hydrogenation active sites on these Cu based
catalysts. The average Cu particle size on the two catalysts is calculated
by Scherrer equation. The obtained results showed that the average
particle size of Cu on reduced Cu-γ-Al2O3 and Cu-HZSM-5 are 22.5 nm
and 21.0 nm, respectively. Clearly, these are bigger than the average
pore diameter of supports, so most of the Cu active species are located
outside of the support's pores.
200
300
400
500
600
700
800
Temperatureꢀćꢁ
Fig. 2. NH3-TPD curves for (a) Ni-γ-Al2O3, (b) Cu-γ-Al2O3, and (c) Cu-HZSM-5.
3.2. Catalyst characterization
3.2.1. N2 sorption and metal dispersion of the catalysts
The specific surface areas and pore structural parameters of the Cu
and Ni based catalysts are summarized in Table 2. The N2 sorption char-
acteristics of Cu-γ-Al2O3 is similar with that of Ni-γ-Al2O3, this demon-
strated that the N2 sorption characteristics of the catalyst are mainly
influenced by the support. Even with the same metal species, the total
pore volume of Cu-HZSM-5 is smaller than that of Cu-γ-Al2O3, while
the surface areas are much bigger than that of Cu-γ-Al2O3. Clearly,
these may be caused by the micro pore structure of HZSM-5. As report-
ed [24], the micro pore structure of the catalysts could inhibit the mass
and heat transfers in reactions. However, the catalyst with higher
mesoporosity shows lower catalytic activity as shown in Table 1. It
does not seem that the mass transfer is as important as the intrinsic
catalytic activity in this reaction.
x104
1.20
Energy: 932.6
1.15
1.10
Energy: 934.3
1.05
Table 4
1.00
0.95
Temperature programmed desorption of NH3 for Ni or Cu based catalysts.
Sample a
Weak acid
(mmol NH3/g)
Strong acid
(mmol NH3/g)
Total acid
(mmol NH3/g)
960
950
940
930
920
Ni-γ-Al2O3
Cu-γ-Al2O3
Cu-HZSM-5
0.19
0.20
0.44
0.03
0.04
0.10
0.22
0.24
0.54
Binding energy (eV)
a
NH3-TPD measurements were conducted on the oxide precursors.
Fig. 4. XPS spectra of Cu on Cu-HZSM-5.

48
X. Kong, L. Chen / Catalysis Communications 57 (2014) 45–49
104
102
100
98
contributes to enhanced hydrogenation activity. Based on the reaction
data and the N2O chemisorptions results, we proposed that a similar
hydrogen spillover may occur on Cu-HZSM-5, since Cu-HZSM-5 sample
was found to be much more active than its counterparts supported on
less acidic substrates as shown in Table 1. So, the enhancement of acid
sites to the hydrogenation of benzaldehyde could be explained as the
hydrogen spillover phenomenon and C–O activation effect.
Based on the above discussions and some literatures [31,32], we
propose that the formation of toluene probably followed the procedures
below . Firstly, benzaldehyde was hydrogenated to alcohol over the
Cu0 species, and then the benzyl alcohols were protonated by the strong
acid sites; at last toluene was formed through the hydrogenolysis of
the protonated species on an adjacent Cu0 site. Actually, the selectivity
towards toluene is determined by the aptitude of the catalyst to both
adsorb the alcohol through acid–base property and dissociate H2 through
metal property.
conversion of benzaldehyde
selectivity toluene
96
94
0
20
40
60
80
100
Time on stream (h)
3.2.4. XPS
Fig. 5. The time on stream performance of Cu-HZSM-5.
As shown in the XPS spectra in Figs. 3 and 4 the peak at 932.6 eV is
assigned to the binding energy of the Cu0 species at the Cu2p3/2 level
[33]. Its presence indicated that the presence of metallic active sites on
the catalyst is mainly in the form of Cu0 species, which is in agreement
with the XRD characterizations. A careful analysis of the Cu2p photo-
electron spectra also shows a weak signal at 934.30 eV in Fig. 4, indicat-
ing that Cu2+ species are also detected in the reduced Cu-HZSM-5. As
mentioned in Experimental Section, Cu-HZSM-5 was shaped in the
presence of alumina as binder. It was reported [34] that CuAl2O4 is
often formed on Cu-Al2O3 catalysts, and these CuAl2O4 crystals are hard-
ly to be reduced under the condition as shown in the present studies
[13,34]. Thus we assume that the trace amounts of Cu2+ is probably
presented in the CuAl2O4 crystal.
3.2.3. NH3-TPD
The NH3-TPD curves of Ni-γ-Al2O3, Cu-γ-Al2O3 and Cu-HZSM-5 are
shown in Fig. 2. The two desorption peaks at the lower temperature
and the higher temperature correspond to the weak and strong acid
sites on the catalyst, respectively. The acidic capacity of these samples
is listed in Table 4, it can be found that the acid sites of Ni-γ-Al2O3 and
Cu-γ-Al2O3 are almost the same, but are less than about 60% of that of
Cu-HZSM-5, this demonstrated that the acid sites on the catalysts are
mainly influenced by the support. In other words, the replacement of
support from γ-Al2O3 to HZSM-5 dramatically increased the acid sites
of Cu based catalyst.
It is generally accepted that the hydrogenation reaction over metals
supported on acidic substrates occurs on metal sites as well as on acid
sites. And, H2 is dissociated on metal sites during the reaction, while O-
containing compounds are adsorbed and activated on either metal sites
or on the cations/oxygen vacancies located at the metal-support inter-
face [25–28]. Thus, it is easy to understand why Cu-HZSM-5 demonstrat-
ed a better hydrogenation/deoxygenation performance than Cu-γ-Al2O3.
As can be found from the N2O chemisorption results, Cu-HZSM-5 and
Cu-γ-Al2O3 have similar Cu dispersions and exposed copper surface
areas. Clearly, it is hard to explain why Cu-HZSM-5 has better hydroge-
nation ability than Cu-γ-Al2O3 only by chemisorption results.
3.3. The stability of Cu-HZSM-5
As can been found in Tables S1 and S2, at the optimum conditions
the conversion of benzaldehyde and selectivity towards toluene
reached to 100.0% and 99.3%, respectively. To further understand the
catalytic performance of Cu-HZSM-5, stability test was performed under
the optimum conditions (temperature 180 °C, H2 pressure 3 MPa) in
the fixed-bed reactor for 100 h, and the results are shown in Fig. 5. For
the duration of the test no notable decreases in activity or selectivity
were observed, which indicated that Cu-HZSM-5 exhibited an excellent
stability. Therefore, the catalyst is promising for pilot plant test.
As reported [29,30], hydrogen spillover is a common feature ob-
served on noble metal catalysts supported on acidic substrates which
Table 5
The hydrodeoxygenation results of aromatic aldehydes over Cu-HZSM-5.
Entry
1
Substrate
Product
Conversion/%
100.0
Selectivity/%
99.3
2
3
100.0
100.0
99.5
99.0
4
5
97.2
98.9
95.1
95.2
Reaction conditions: temperature 180 °C, H2 pressure 3 MPa, GHSV 150 h−1 (pure H2), LHSV 0.6 h−1
.

X. Kong, L. Chen / Catalysis Communications 57 (2014) 45–49
49
3.4. Generality of Cu-HZSM-5
References
[1] J.T. Kuethe, K.G. Childers, Z. Peng, M. Journet, G.R. Humphrey, T. Vickery, D. Bachert,
T.T. Lam, Org. Process Res. Dev. 13 (2009) 576.
The generality of Cu-HZSM-5 was investigated through a series of
aromatic aldehydes, the obtained results are summarized in Table 5. It
can be found that the established process appears to be effective for
the hydrogenation of aromatic aldehydes. Most of the selected alde-
hydes could be transformed to the corresponding aromatic hydrocar-
bon with selectivity more than 95.0%. The exceptions, benzophenone
(entry 4) and 3,4,5-trimethoxybenzaldehyde (entry 5) were deoxygen-
ated in a relatively low yield, these results may be caused by the steric
hindrance effect. All in all, the catalyst was proved to be effective for
the hydrogenation of a series of aromatic aldehydes to corresponding
aromatic hydrocarbons.
[2] D.V. Nadkarni, J.F. Hallissey, Org. Process Res. Dev. 12 (2008) 1142.
[3] A.M. Alotaibi, E.F. Kozhevnikova, I.V. Kozhevnikov, Chem. Commun. 48 (2012) 7194.
[4] C. Zhao, J.A. Lercher, Angew. Chem. Int. Ed. 51 (2012) 5935.
[5] X.J. Kong, W.C. Lai, J. Tian, Y. Li, X.L. Yan, L.G. Chen, ChemCatChem 5 (2013) 2009.
[6] F. Alvarez, P. Magnoux, F.R. Ribeiro, M. Guisnet, J. Mol. Catal. 92 (1994) 67.
[7] L.X. Xing, X.Y. Wang, C.J. Cheng, et al., Tetrahedron 63 (2007) 9382.
[8] T.J. Connolly, M. Matchett, P. McGarry, S. Sukhtankar, J. Zhu, Org. Process Res. Dev. 8
(2004) 624.
[9] X.F. Guo, D.Y. Jang, H.G. Jang, G.J. Kim, Catal. Today 186 (2012) 109.
[10] M.A. Vannice1, D. Poondi, J. Catal. 169 (1997) 166.
[11] M.V. Bykova, D.Yu. Ermakov, V.V. Kaichev, O.A. Bulavchenko, A.A. Saraev, M.Yu.
Lebedev, V.A. Yakovlev, Appl. Catal. B 113 (2012) 296.
[12] W.Y. Wang, Y.Q. Yang, H. Luo, T. Hu, W.Y. Liu, Catal. Commun. 12 (2011) 436.
[13] J.C. Ma, S. Liu, X.J. Kong, X.P. Fan, X.L. Yan, L.G. Chen, Res. Chem. Intermed. 38 (2012)
1341.
4. Conclusion
[14] W.J. Song, C. Zhao, J.A. Lerche, Chem. Eur. J. 19 (2013) 9833.
[15] I.D. Mora, E. Méndez, L.J. Duarte, S.A. Giraldo, Appl. Catal. A 474 (2014) 59.
[16] X.H. Zhang, Q. Zhang, L.A. Chen, Y. Xu, T.J. Wang, L.L. Ma, Chinese J. Catal. 35 (2014) 302.
[17] S. Sato, R. Takahashi, T. Sodesawa, K. Yuma, Y. Obata, J. Catal. 196 (2000) 195.
[18] J. Zhang, D.H. He, J. Colloid Interface Sci. 419 (2014) 31.
[19] S. Liu, X.P. Fan, X.L. Yan, X.B. Du, L.G. Chen, Appl. Catal. A 400 (2011) 99.
[20] M.L. Barbelli, G.F. Santori, N.N. Nichio, Bioresour. Technol. 111 (2012) 500.
[21] Z.J. Wu, Y.Z. Mao, M. Song, et al., Catal. Commun. 32 (2013) 52.
[22] R.J. Rahaim Jr., R.E. Maleczka Jr., Org. Lett. 13 (2011) 585.
[23] S.N. Delgado, D. Yap, L. Vivier, C. Especel, J. Mol. Catal. A Chem. 367 (2013) 89.
[24] S.D. Kim, S.C. Baek, Y.J. Lee, K.W. Jun, M.J. Kim, I.S. Yoo, Appl. Catal. A 309 (2006) 139.
[25] G.W. Huber, S. Iborra, A. Corma, Chem. Rev. 106 (2006) 4044.
[26] D.C. Elliot, Energy Fuels 21 (2007) 1792.
A continuous process for the hydrogenation of aromatic aldehydes
over Cu-HZSM-5 in a fixed-bed reactor was established. Cu0 is believed
to be the main active species for the hydrogenation. The HZSM-5 sup-
port promised the catalyst has a strong acidity, and the participation
of acid sites in the enhancement of hydrogenation ability of the catalysts
was explained as due to the hydrogen spillover phenomenon and the
C–O activation effect. In addition, the catalyst was proved to be effective
for the hydrogenation of a series of aromatic aldehydes.
[27] C.R. Lee, J.S. Yoon, Y.W. Suh, J.W. Choi, J.M. Ha, D.J. Suh, Y.K. Park, Catal. Commun. 17
(2012) 54.
[28] S. Echeandia, B. Pawelec, V.L. Barrio, P.L. Arias, J.F. Cambra, C.V. Loricera, J.L.G. Fierro,
Fuel 117 (2014) 1061.
Acknowledgment
This work is supported by the Natural Science Foundation of China
(Under Grant No. 21406103).
[29] P.M. Mortensen, J.D. Grunwldt, P.A. Jensen, K.G. Knudsen, A.D. Jensen, Appl. Catal. A 407
(2011) 1.
[30] Z. He, X. Wang, Catal. Sustain. Energy 1 (2012) 28.
[31] A. Saadi, R. Merabti, Z. Rassoul, M.M. Bettahar, J. Mol. Catal. A Chem. 253 (2006) 79.
[32] C.A. Koutstaal, P.A.J.M. Angevaare, V. Ponec, J. Catal. 143 (1993) 573.
[33] T. Ghodselahi, M.A. Vesaghi, A. Shafiekhani, A. Baghizadeh, M. Lameii, Appl. Surf. Sci.
255 (2008) 2730.
Appendix A. Supplementary data
Supplementary data to this article can be found online at http://dx.
doi.org/10.1016/j.catcom.2014.07.038.
[34] F. Yang, Z.W. Wu, J.C. Ma, H.B. Wang, Y. Li, L.G. Chen, Catal. Lett. 141 (2011) 1142.