Optimized benzaldehyde production over a new Co-ZSM-11 catalyst: Reaction parameters effects and kinetics

Article abstract of DOI:10.1016/j.catcom.2013.11.020

An efficient Co-ZSM-11 catalyst has been synthesized for benzaldehyde production by the selective styrene oxidation. Reaction parameters such as catalyst mass, reaction temperature, molar ratio styrene/hydrogen peroxide and stirring speed were optimized, by performing the styrene oxidation reaction in a stirred batch system with fine particles of Co-ZSM-11 in suspension under microwave heating. A kinetic study was done by using the initial rate method and the Arrhenius parameters were estimated. This catalyst presents a higher reaction rate about 30% with respect of those found in literature and a higher selectivity towards benzaldehyde about 80% at optimal conditions.

Full text of DOI:10.1016/j.catcom.2013.11.020

Catalysis Communications 46 (2014) 6–10
Contents lists available at ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short Communication
Optimized benzaldehyde production over a new Co-ZSM-11 catalyst:
Reaction parameters effects and kinetics
Federico Azzolina Jury a,b,c,1, Isabelle Polaert b, , Liliana B. Pierella a,c, Lionel Estel b
⁎
a
CITeQ (Centro de Investigación Tecnología Química), Universidad Tecnológica Nacional, 5016 Córdoba, Argentina
LSPC (Laboratoire de Sécurité des Procédés Chimiques), INSA, Rouen, France
CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas), Argentina
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 4 October 2013
Received in revised form 15 November 2013
Accepted 20 November 2013
Available online 27 November 2013
An efficient Co-ZSM-11 catalyst has been synthesized for benzaldehyde production by the selective styrene ox-
idation. Reaction parameters such as catalyst mass, reaction temperature, molar ratio styrene/hydrogen peroxide
and stirring speed were optimized, by performing the styrene oxidation reaction in a stirred batch system with
fine particles of Co-ZSM-11 in suspension under microwave heating. A kinetic study was done by using the initial
rate method and the Arrhenius parameters were estimated. This catalyst presents a higher reaction rate about
30% with respect of those found in literature and a higher selectivity towards benzaldehyde about 80% at optimal
conditions.
Keywords:
Microwave
Co-ZSM-11
© 2013 Elsevier B.V. All rights reserved.
Styrene oxidation
Benzaldehyde
Kinetic parameters
1. Introduction
than those presented above. Despite this fact, most of the catalysts
used in this process are homogeneous noble metal-organic compounds
The catalytic partial oxidation is an important source of research at
different levels, from the industrial production of commodities to the
small amount synthesis of pharmaceuticals and fine chemicals. The con-
tinuing development of new catalysts is a key point for the catalytic ox-
idation processes in order to reduce or eliminate the separation stages
and to reduce the generation of pollutants by developing processes
compatible with the environment.
Styrene catalytic oxidation for benzaldehyde production is of great
interest for academic research as well as for industrial use [1]. Benzalde-
hyde is a very important fine chemical that is used in many fields such
as medicine, dyes, flavors and resin additive. It is also an important in-
termediate in the synthesis of perfumes, pharmaceuticals and agro-
chemicals. Commercially, it can be obtained by catalytic oxidation of
toluene to benzoic acid with oxygen in the liquid phase and in the pres-
ence of bromine-promoted cobalt and manganese catalysts [2]. Benzal-
dehyde can also be produced by the hydrolysis of benzal chloride. This
process employs environmentally undesirable organic solvents as tolu-
ene and the benzaldehyde produced contains traces of chlorine and in
the latter process, the selectivity for benzaldehyde is very poor [3,4]. An-
other way of benzaldehyde production is the styrene selective oxidation
using hydrogen peroxide as oxidant agent. It offers the advantages of a
production without chlorine traces that make this process greener
like ruthenium (II) perchlorate complexes [5,6]. The product separation
from the catalyst is a common problem. Thus, it is important to develop
novel and active heterogeneous catalysts for benzaldehyde production.
In a previous study, Azzolina Jury et al. [7] have developed ZSM-11
zeolites doped with transition metals like Co, Fe, Cr, Ni, Mn and Zn
showing a significant catalytic activity improvement on the styrene par-
tial oxidation reaction at mild conditions under microwave irradiation.
Microwave heating has shown no influence on the catalytic efficiency
compared to classical heating [7], but it is an ideal mean of controlling
accurately the reaction parameters like temperature [8]. Thus, this
heating mode was adopted in the present study.
Benzaldehyde can be synthesized trough two pathways [9–11] as
shown in Fig. 1.
One possible way is the oxidation of the side chain by a radical mech-
anism by causing the cleavage of the C_C bond to form benzaldehyde
(1′). It could also be obtained by an epoxidation reaction to form styrene
oxide (1) which would then be nucleophilically attacked to form benz-
aldehyde (2). The first pathway (1′) is favored at low temperatures and
it allows the synthesis of benzaldehyde with a high selectivity towards
this product. Otherwise, through the second pathway, benzaldehyde
could be obtained but with significant amounts of epoxide reaction
products like styrene oxide and phenylacetaldehyde.
In this study, the Co-ZSM-11 zeolite was employed in the styrene
partial oxidation using hydrogen peroxide as oxidizing agent. This zeo-
lite showed the highest activity in the catalytic partial oxidation of sty-
rene in an earlier study [8] compared to other doped zeolites where
⁎
Corresponding author. Tel.: +33 232 956 654; fax: +33 232 956 652.
E-mail address: Isabelle.Polaert@insa-rouen.fr (I. Polaert).
Tel./fax: +54 351 4690 585.
1
1566-7367/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.catcom.2013.11.020

F. Azzolina Jury et al. / Catalysis Communications 46 (2014) 6–10
7
Fig. 1. Reaction scheme for styrene oxidation.
Table 1
Characterization of Co-ZSM-11 zeolite.
Zeolite
Surface area
[m2·g−1
Transition metal
content [wt.%]
Exchange level
[%]
Lewis acid sites
Brönsted acid sites
L/B
3.0
]
[μmol pyridine·mg·cat.−1
]
[μmol pyridine·mg·cat.−1
]
Co-ZSM-11
318
1.87
36
0.15
0.05
benzaldehyde was obtained as main product. The goal of this work is
first to optimize the reaction conditions for benzaldehyde production
by evaluating several reaction parameters such as reaction temperature,
stirring speed, molar ratio substrate/hydrogen peroxide and catalyst
mass. The second aim is to propose an accurate kinetics of the reaction
under optimized conditions.
2. Experimental
2.1. Catalysts preparation
The ZSM-11 zeolite was obtained by hydrothermal synthesis and
doped by ionic exchange as detailed in an earlier study [7].
Fig. 2. System for styrene partial oxidation.

8
F. Azzolina Jury et al. / Catalysis Communications 46 (2014) 6–10
Fig. 5. Reaction temperature influence on styrene conversion. Reaction conditions:
R = 0.9; 0.2 g of Co-ZSM-11; 350 rpm.
Fig. 3. Catalyst mass effect on styrene conversion. Reaction conditions: T = 60 °C; n0 CH3
CN:0.465 mol; n0 C8H8: 0.016 mol; n0 H2O2: 0.019 mol; 350 rpm.
2.2. Catalyst characterization
3. Results and discussion
A complete characterization study of Co-ZSM-11 zeolite was per-
formed in an earlier study [7]. Table 1 resumes the characterization
data of this zeolite.
3.1. Optimization of the reaction parameters
The styrene partial oxidation reaction was evaluated at two different
stirring speeds of 250 and 350 rpm.
No influence of the stirring rate on the styrene partial oxidation reac-
tion was observed. This experiment verifies that the stirring speed of
350 rpm is adequate to ensure the absence of external diffusion resis-
tances within the liquid system and the correct suspension of the fine
catalyst particles in the reaction system [12]. This value (350 rpm)
will be used in all this study.
2.3. Catalytic activity measurements
The styrene partial oxidation was carried out by using hydrogen per-
oxide as oxidizing agent and acetonitrile as solvent. The reactions were
performed under microwave irradiation inside a WR-340 waveguide
with a temperature control of
0.3 °C.
Co-ZSM-11 zeolite was under the form of fine particles (0.5 μm in di-
ameter) suspended in the reaction medium under agitation of 350 rpm
(Fig. 2).
The organic products were analyzed and quantified by gas chroma-
tography. A sample of the reaction solution was analyzed by ICP, after
completion of the reaction, in order to determine the concentration
of cobalt ions Co2+ in the reaction medium. It was found to be null
(0.00 ppm) for each experiment presented in this study, confirming
the leaching absence of Co2+ ions from the zeolite.
3.1.1. Influence of catalyst mass
In order to evaluate the influence of the Co-ZSM-11 mass, the sty-
rene oxidation reaction was carried out with different catalyst masses
under identical conditions.
The styrene conversion and the reaction rates are increased by the
catalyst mass. But, the initial reaction rate is not proportional to the
catalyst mass (Fig. 3). This fact is probably caused by the decomposition
of hydrogen peroxide which is favored by the increase of the catalyst
concentration [4]. This fact will be considered in the kinetic study
through the determination of the apparent order with respect to the
catalyst concentration.
3.1.2. Influence of C8H8/H2O2 molar ratio (R)
The styrene partial oxidation was carried out at different R values by
varying H2O2 amount: 0.21, 0.40, 0.85 and 1.89. As the ratio R increases,
the styrene conversion after 7 h of reaction decreases (Fig. 4). This is
due to the concentration diminution of the oxidant in the reaction
Table 2
Temperature influence on reaction products selectivity.
Reaction
Styrene
Selectivity
Selectivity
Selectivity
temperature conversion benzaldehyde styrene oxide phenylacetaldehyde
[°C]
[mol%]
[mol%]
[mol%]
[mol%]
40
50
60
70
80
7
16
31
45
25
100
80
81
67
81
0
20
15
21
9
0
0
4
12
10
Fig. 4. Effect of C8H8/H2O2 molar ration on styrene conversion and selectivity to benzalde-
hyde, styrene oxide and phenylacetaldehyde. Reaction conditions: 0.4 g of Co-ZSM-11;
T = 60 °C; 350 rpm.

F. Azzolina Jury et al. / Catalysis Communications 46 (2014) 6–10
9
Table 3
Co-ZSM-11 efficiency on styrene oxidation with respect to other catalysts found in literature.
Reference
Catalyst
Temperature [°C]
Selectivity towards benzaldehyde (mol%)
Efficiency [g·sty·g·cat.−1·h−1
]
Efficiency [g·sty·g·metal−1·h−1
]
[15]
[13]
[13]
[13]
[16]
[17]
[18]
[18]
[18]
[19]
[19]
[20]
[14]
[14]
[14]
[14]
TS-1
60
173
70
70
50
70
60
60
60
60
60
60
60
60
60
60
60
60
60
70
29
63
65
55
0
0.11
1.13
0.21
0.27
0.35
0.29
0.27
0.22
0.26
–
1.7
18.9
5.4
3.1
–
Fe-ZSM-5 (0.6 wt.%)
Co-VSB-5 (3.98 wt.%)
Co-VSB-5 (8.78 wt.%)
LaCo-MCM-41
Sr-Fe2O4
Ni-Fe2O4
Zn-Fe2O4
Fe3O4
MnX
64
55
50
68
55
53
80
72
71
67
89
90
90
81
67
–
–
–
–
20.8
18.9
8.5
15.5
16.8
4.4
16.4
1.2
25.6
19.8
28.9
MnY
Co-ZSM-5
–
0.23
0.43
0.42
0.13
0.47
0.06
0.22
0.37
0.54
Co-ZSM-5 (2.80 wt.%)
Zn-ZSM-5 (2.50 wt.%)
Cu-ZSM-5 (3.00 wt.%)
Fe-ZSM-5 (2.90 wt.%)
Co-Y (5.13 wt.%)
Co-ZSM-11 (0.86 wt.%)
Co-ZSM-11 (1.87 wt.%)
Co-ZSM-11 (1.87 wt.%)
[7]
[7]
This article
This article
medium. Also, an increase in selectivity towards benzaldehyde is ob-
served when decreasing R. The selectivity values towards styrene
oxide do not present any significant variation with R. Nevertheless,
the selectivity values to phenylacetaldehyde, as a consequence of the
epoxidation reaction, increase with R. Thus, the optimum value of R is
0.2. Below this value, at higher hydrogen peroxide concentration, a co-
balt active species leaching causing catalyst activity loss was observed.
Another disadvantage of the high hydrogen peroxide concentration
is that it can also oxidize the stationary phase of the chromatographic
column and produce permanent damage. For that reason, we decided
to perform the rest of the study with R = 0.9 despite the fact that
R = 0.2 is the optimum value.
Co-ZSM-11 (0.86 wt.%) zeolite, prepared and synthesized in an ear-
lier study [7], and Co-ZSM-11 (1.87 wt.%) present the highest catalytic
efficiency, expressed in grams of styrene transformed per transition
metal mass (25.61 and 19.79 g·sty·g·metal−1·h−1 respectively). How-
ever, the low metal content of Co-ZSM-11 (0.86 wt.%) leads to the need
of using higher mass of catalyst in order to reach the same efficiency
than Co-ZSM-11 (1.87 wt.%) zeolite. Thus, Co-ZSM-11 (1.87 wt.%) pre-
sents a higher efficiency value per catalyst mass than Co-ZSM-11
(0.86 wt.%) zeolite (0.37 vs. 0.22). Compared to the catalysts found in
literature, Co-ZSM-11 (1.87 wt.%) zeolite used in this work, presents
the highest catalytic activity for the styrene partial oxidation at mild
conditions (60 °C) and selectivity towards benzaldehyde.
3.2. Kinetic study
3.1.3. Effect of the reaction temperature
The styrene conversion increases with temperature from 40 °C to
70 °C (Fig. 5). At 80 °C, the styrene oxidation reaction stops after 2 h
which is not observed for the other temperatures.
This phenomenon is mainly attributed to the hydrogen peroxide
decomposition reaction after 2 h of reaction, at 80 °C. Gao et al. [13]
have also found that the styrene conversion and selectivity towards
benzaldehyde was diminished beyond 80 °C due to the hydrogen per-
oxide decomposition over Co-VSB-1 catalyst.
To determine the kinetic parameters of the styrene oxidation reac-
tion under microwave irradiation, the initial rate kinetic method was
applied in the absence of external and internal diffusional resistances
[8,14,21]. In this study, the initial reaction rates were evaluated from
the consumed amount of styrene as a function of time. Initial reaction
rates were calculated from the tangent slopes of the styrene concentra-
tion curves at time zero [14]. Thus, a kinetic model was proposed in
order to predict the styrene concentration as a function of reaction time.
In order to obtain the kinetic order with respect to the hydrogen per-
oxide concentration, the reaction was carried out by varying the concen-
trations of the oxidizer while maintaining constant the concentrations of
The data at 80 °C will not be used for activation energy determina-
tion. Thus, the kinetic model developed in this work will only be valid
for reaction conditions up to 70 °C.
The temperature increase produces a decrease in the selectivity
towards benzaldehyde. But the selectivity towards the epoxidation
products (like styrene oxide and phenylacetaldehyde) becomes more
significant (Table 2). The breaking of the C_C bond is more favorable
at low temperatures, while at higher temperatures the epoxidation
reaction competes more favorably with the cleavage of the C_C [14].
From 60 °C, the selectivity towards benzaldehyde is greatly de-
creased. Thus, the optimum working temperature for this reaction is
60 °C.
The styrene conversion and selectivity towards benzaldehyde
values, for different catalysts found in literature, are shown in Table 3.
Table 4
Kinetic constant values from 40 to 70 °C.
T [°C]
k [L·g−0.5·mol−0.5·h−1
]
ln (k)
40
50
60
70
0.0052
0.0142
0.0248
0.0580
−2.28
−1.84
−1.60
−1.24
Fig. 6. Arrhenius plot of the pseudo first order rate kinetic constants of styrene oxidation
over Co-ZSM-11.

10
F. Azzolina Jury et al. / Catalysis Communications 46 (2014) 6–10
acetonitrile and styrene, the mass of catalyst, temperature and stirring
speed. A linear increase of the initial reaction rate with respect to the
square root of the hydrogen peroxide concentration was found. This
fact may be explained by the increase of the initial reaction rate of the
non-desirable hydrogen peroxide decomposition.
To determine the kinetic order with respect to the styrene concen-
tration, the reaction was carried out by varying the concentrations of
this reagent while maintaining constant the concentrations of acetoni-
trile and hydrogen peroxide, the mass of catalyst, temperature and
stirring speed. A linear increase of the initial reaction rate with respect
to the styrene concentration was found.
with the catalyst mass, but a nonlinear function between the initial reac-
tion rate and the catalyst concentration was found. This fact is caused by
the increase of the non-desirable hydrogen peroxide decomposition
reaction rate with the catalyst mass and with temperature.
Kinetics of the reaction was determined from 40 to 70 °C. The reac-
tion rate is of first order with respect to the styrene concentration and a
fractional order with respect to the oxidant concentration is suggested.
The apparent activation energy obtained is 30.2 kJ·mol−1 with a high
pre-exponential factor of the Arrhenius expression. This kinetics will
be used for further reactor calculations for benzaldehyde production
in continuous mode under microwave.
The effect of the catalyst concentration on the reaction rate was
studied at fixed initial styrene and hydrogen peroxide concentrations.
An apparent fractional order of 0.5 with respect to the catalyst concen-
tration was found.
Acknowledgments
The authors want to thank the LSPC and CITeQ laboratories for their
As discussed in Section 3.1.1, this fact could be caused by the in-
crease of the initial reaction rate of the hydrogen peroxide decomposi-
tion with the catalyst mass [4].
financial support.
Appendix A. Supplementary data
The law for the reaction rate is:
Supplementary data to this article can be found online at http://dx.
doi.org/10.1016/j.catcom.2013.11.020.
½
r ¼ ½Ccatꢀ k½C8H8ꢀ½H2O2ꢀ1=2
:
References
The kinetic constant was calculated from the initial reaction rates
values, reagent concentrations and catalyst mass for each temperature
between 40 and 70 °C (Table 4).
[1] J. Liu, F. Wang, Z. Gu, X. Xu, Chem. Eng. J. 151 (2009) 319–323.
[2] J.I. Kroschwitz, 4th ed., Kirk Othmer Encyclopedia of Chemical Technology, vol. 4,
Wiley-Interscience Publications, New York, 1992. 64–72.
[3] V.R. Choudhary, P.A. Chaudhari, V.S. Narkhede, Catal. Commun. 4 (2003) 171–175.
[4] A. Jia, L. Lou, C. Zhang, Y. Zhang, S. Liu, J. Mol. Catal. A 306 (2009) 123–129.
[5] A.S. Kanmani, S. Vancheesan, J. Mol. Catal. A 150 (1999) 95–104.
[6] A.M. Al-Ajiouni, J.H. Espenson, J. Am. Chem. Soc. 117 (1995) 9243–9250.
[7] F. Azzolina Jury, I. Polaert, L. Estel, L.B. Pierella, Appl. Catal. A Gen. 453 (2013)
92–101.
[8] I. Polaert, M. Cunha Felix, M. Fornasero, S. Marcotte, J.C. Buvat, L. Estel, Chem. Eng. J.
222 (2013) 228–239.
[9] M.R. Maurya, A.K. Chandrakar, S. Chand, J. Mol. Catal. A Chem. 274 (2007) 192–201.
[10] V. Hulea, E. Dumitriu, Appl. Catal. A Gen. 277 (2004) 99–106.
[11] S. Gomez, L. Garces, J. Villegas, R. Ghosh, O. Giraldo, S. Suib, J. Catal. 233 (2005)
60–67.
The apparent activation energy obtained from the slope of the line is
30.2 kJ·mol−1 and the frequency factor is 11,335 l·g−0.5·mol−0.5·h−1
(Fig. 6). The order of magnitude of the apparent activation energy is
correct, compared to the value found by Saux and Pierella [14] on a
Co-ZSM-5 zeolite. On the other hand, the frequency factor is higher
but this value can be explained by the different zeolite structures
employed for the styrene oxidation kinetic study. In addition, the tran-
sition metal content and the ion distributions in the zeolite framework
are not certainly the same for the Co-ZSM-11zeolite used in this study
and for those employed in literature [14].
[12] O. Levenspiel, 3rd ed., Chemical Reaction Engineering, John Wiley and sons, 1999.
396 [Chap. 18].
[13] D. Gao, Q. Gao, Microporous Mesoporous Mater. 85 (2005) 365–373.
[14] C. Saux, L.B. Pierella, Appl. Catal. A Gen. 400 (2011) 117–121.
[15] J. Zhuang, D. Ma, Z. Yan, X. Liu, X. Han, X. Bao, Y. Zhang, X. Guo, X. Wang, Appl. Catal.
258 (2004) 1–6.
[16] V. Parvulescu, C. Anastasescu, B.L. Sub, J. Mol. Catal. A Chem. 211 (2004) 143–148.
[17] S.K. Pardeshi, R.Y. Pawar, J. Mol. Catal. A Chem. 334 (2011) 35–43.
[18] D. Guin, B. Baruwati, S.V. Manorama, J. Mol. Catal. A Chem. 242 (2005) 26–31.
[19] M. Silva, C. Freire, B. de Castro, J.L. Figueiredo, J. Mol. Catal. A Chem. 258 (2006)
327–333.
[20] L.B. Pierella, C. Saux, S.C. Caglieri, H.R. Bertorello, P.G. Bercoff, Appl. Catal. A Gen. 347
(2008) 55–61.
[21] I. Bergault, P. Fouilloux, C. Joly-Vuillemin, H. Delmas, J. Catal. 175 (1998)
328–337.
4. Conclusions
An efficient catalyst Co-ZSM-11 was synthesized and the optimal
reaction conditions for benzaldehyde production from partial styrene
oxidation were found. This catalyst has the highest efficiency with
respect to the mass of the transition metal.
The optimal molar ratio substrate/oxidant is 0.2. The optimal temper-
ature found for this reaction is 60 °C. The styrene conversion increases
with temperature, however from 60 °C the generation of styrene epoxi-
dation products becomes significant. The styrene conversion increased