Composites based on modified clay assembled Rh(III)–heteropolymolybdates as catalysts in the liquid-phase hydrogenation of cinnamaldehyde

Article abstract of DOI:10.1016/j.crci.2015.09.015

New composites based on the [RhMo₆O₂₄H₆]^3? (RhMo₆) heteropolyanion supported on pillared (PILC), heterostructured (PCH) and functionalized(PILC-F) and (PCH-F) systems based on clays were prepared, characterized and tested as catalysts in the liquid-phase hydrogenation of cinnamaldehyde. The original phases and supported systems were characterized using several techniques such as powder X-ray diffraction (XRD), scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM–EDS), Raman microprobe studies, X-ray photoelectron spectroscopy (XPS), thermogravimetry and differential thermal analyses (TG-DSC), temperature programmed reduction (TPR), and textural analysis (BET method), which confirmed their functionalization, physicochemical modification and the nature of Mo adsorbed species. Active acidic, basic and redox sites were determined by temperature programmed surface reaction (TPSR). Mo loading reached 7?wt% for the system RhMo₆/PCH-F and 3?wt% for the system RhMo₆/PILC-F, while unfunctionalized clay systems showed a value of 1?wt% of Mo. The catalytic performance showed that PCH-based composites were the most active and reached up to 56% conversion at 360?min of reaction when tested in liquid-phase cinnamaldehyde hydrogenation. The selectivity for all the systems was mainly toward hydrocinnamic aldehyde (HCAL) and reached 77% for the RhMo₆/PCH-F catalyst at 25% conversion.

Full text of DOI:10.1016/j.crci.2015.09.015

C. R. Chimie xxx (2015) 1e10
Contents lists available at ScienceDirect
Comptes Rendus Chimie
www.sciencedirect.com
ꢀ
Full paper/Memoire
Composites based on modified clay assembled
Rh(III)eheteropolymolybdates as catalysts in the liquid-phase
hydrogenation of cinnamaldehyde
,
, b, c, d
Guillermo R. Bertolini a b, Virginia Vetere a, María A. Gallo a
,
a
a
a
~
ꢀ
Mercedes Munoz , Monica L. Casella , Luís Gambaro ,
, b, c, *
Carmen I. Cabello a
a
ꢀ
Centro de Investigacion y Desarrollo en Ciencias Aplicadas “Dr. Jorge J. Ronco”-CINDECA (CONICET-CCT La Plata-UNLP), Universidad
Nacional de La Plata, Facultad de Ciencias Exactas, calle 47 nꢀ 257, 1900, B1900AJK La Plata, Argentina
b Facultad de Ingeniería UNLP, Argentina
c Member of CICPBA, Argentina
d
ꢁ
Universita di Roma “La Sapienza”, P.le A. Moro 5, 00185 Roma, Italy
a r t i c l e i n f o
a b s t r a c t
New composites based on the [RhMo6O24H6]3ꢁ (RhMo6) heteropolyanion supported on
pillared (PILC), heterostructured (PCH) and functionalized(PILC-F) and (PCH-F) systems
based on clays were prepared, characterized and tested as catalysts in the liquid-phase
hydrogenation of cinnamaldehyde. The original phases and supported systems were
characterized using several techniques such as powder X-ray diffraction (XRD), scanning
electron microscopy and energy-dispersive X-ray spectroscopy (SEMeEDS), Raman
microprobe studies, X-ray photoelectron spectroscopy (XPS), thermogravimetry and dif-
ferential thermal analyses (TG-DSC), temperature programmed reduction (TPR), and
textural analysis (BET method), which confirmed their functionalization, physicochemical
modification and the nature of Mo adsorbed species. Active acidic, basic and redox sites
were determined by temperature programmed surface reaction (TPSR). Mo loading
reached 7 wt% for the system RhMo6/PCH-F and 3 wt% for the system RhMo6/PILC-F, while
unfunctionalized clay systems showed a value of 1 wt% of Mo. The catalytic performance
showed that PCH-based composites were the most active and reached up to 56%
conversion at 360 min of reaction when tested in liquid-phase cinnamaldehyde hydro-
genation. The selectivity for all the systems was mainly toward hydrocinnamic aldehyde
(HCAL) and reached 77% for the RhMo6/PCH-F catalyst at 25% conversion.
Article history:
Received 15 May 2015
Accepted 24 September 2015
Available online xxxx
Dedicated to our good friend Professor
Edmond Payen in recognition of his
outstanding contribution to Catalysis.
Keywords:
Rh(III)-heteropolymolybdates
Clays
Composites
Chemical modification
Liquid-phase hydrogenation
Cinnamaldehyde
ꢀ
© 2015 Published by Elsevier Masson SAS on behalf of Academie des sciences.
1. Introduction
The selective hydrogenation of
a,b-unsaturated alde-
hydes assisted by supported metal catalysts is a key stage in
the preparation of pharmaceutical products, flavors and
fragrances[1e3]. Cinnamaldehyde (CAL) selective hydro-
genation is a good example of this commercially important
process that allows obtaining cinnamic alcohol (CA),
hydrocinnamaldehyde (HCAL) and hydrocinnamic alcohol
ꢀ
* Corresponding author. Centro de Investigacion
y Desarrollo en
Ciencias Aplicadas “Dr. Jorge J. Ronco”-CINDECA (CONICET-CCT La
Plata-UNLP), Universidad Nacional de La Plata, Facultad de Ciencias
Exactas, calle 47 nꢀ 257, 1900, B1900AJK La Plata, Argentina.
E-mail address: ccabello@quimica.unlp.edu.ar (C.I. Cabello).
http://dx.doi.org/10.1016/j.crci.2015.09.015
ꢀ
1631-0748/© 2015 Published by Elsevier Masson SAS on behalf of Academie des sciences.
Please cite this article in press as: G.R. Bertolini, et al., Composites based on modified clay assembled Rh(III)ehetero-
polymolybdates as catalysts in the liquid-phase hydrogenation of cinnamaldehyde, Comptes Rendus Chimie (2015), http://
dx.doi.org/10.1016/j.crci.2015.09.015

2
G.R. Bertolini et al. / C. R. Chimie xxx (2015) 1e10
or 3-phenylpropanol (PP). Cinnamic alcohol is a valuable
product in the perfume industry for its aroma as well as for
its fixation properties. Also, it is used in the pharmaceutical
industry in the synthesis of chloromycetin antibiotic [4,5].
More recently, important applications were found for HCAL
such as its use as an intermediate in the synthesis of
medicines for HIV treatment [6e8].
Anderson-type heteropolyoxomolybdate of formula
(NH4)3[RhMo6O24H6].7H2O supported on Argentinean
functionalized clays (PCH-F and PILC-F) to be used as cat-
alysts
in
the
liquid-phase
hydrogenation
of
cinnamaldehyde.
2. Materials and experimental procedure
Although extensive research has been carried out on the
preparation of catalysts for the selective hydrogenation of
cinnamaldehyde to CA or HCAL, there is no single study
that adequately covers the origin of the selectivity [9e11].
In particular, several attempts have been made to synthe-
size catalysts based on selective noble metals toward HCAL.
Bimetallic catalysts have been found to exhibit an impor-
tant synergetic effect that promotes the selectivity to HCAL.
Also, catalysts based on Rh are some of the most effective
catalysts for selective hydrogenation [12].
2.1. Materials
The heteropolymolybdate (NH4)3[RhMo6O24H6]$7H2O
(hereafter RhMo6) was synthesized from the aqueous so-
lution reaction of ammonium heptamolybdate and
RhCl.36H2O in stoichiometric proportions as previously re-
ported [14e17]. Its characterization was conducted by X-
ray powder diffraction, FTIR and Raman Microprobe
vibrational spectroscopies, following previously reported
methods [14, 15].
The selected bentonite clay was extracted from an
Argentine deposit and was provided by MINMARCO S.A.
company as the original material enriched in the mont-
morillonite fraction by Stokes' method. This mineral has
the molecular formula Mx(Al2ꢁxMgx)(Si4)O10(OH)2$nH2O,
where Mx are interlayer cations (Naþ, Kþ, etc.). Chemical
modification of this material by conventional techniques
allowed PILCs (pillared clays) and PCHs (porous clay het-
erostructures) to be obtained [29].
In general, species based on heteropolyacids or poly-
oxometalates (HPOMs), both as bulk and supported sys-
tems, have started to replace
a large number of
conventional oxide precursors, improving the efficiency
and environmental conditions of several catalytic processes
[13e17].
Recent studies have shown that the Rh(III)-
heteropolymolybdate with Anderson-type structure sup-
ported on gamma alumina is an interesting precursor in
heterogeneous catalysis for the selective hydrogenation
process of cinnamaldehyde toward HCAL[18]. Such studies
have shown that the planar structure of the hetero-
polyoxoanion as well as its redox and solubility properties
To prepare PILC,
([AlO4Al12(OH)24(H2O)12
a
]
7þ solution of [Al13
] oligomer
) was used as the pillaring
agent. The clay was treated and shaken with the pillaring
solution at 25 ꢀC for 2 h. The material obtained was filtered,
are key factors in the heteropolyanion-g-alumina interac-
ꢀ
ꢀ
tion process, producing an active surface with an ordered
surface and uniform deposition of Rh and Mo, which favors
the synergetic effect allowing a high catalytic activity and
high yield of HCAL.
washed, dried at 80 C and calcined at 550 C.
PCH was prepared by mixing the bentonite clay with the
cetyl-trimethyl-ammonium-bromide (HDTMA-Br) surfac-
tant, and then the mixture was continuously shaken for
24 h. Tetraethyl-orthosilicate (TEOS) was added as a source
of silica and the mixture was shaken again at room tem-
perature for 4 h. The product obtained was filtered and
In the present paper, a Rh(III)-containing Anderson
phase has been synthesized and deeply characterized by
physicochemical analysis. This phase was employed for the
preparation of composites by equilibrium impregnation on
natural aluminosilicates from Argentinean deposits
(bentonite clay), previously modified and functionalized by
different techniques so that they can be used as catalytic
supports. Clays and their synthetic derivatives or those
obtained by chemical modification are widely used in many
applications as they exhibit specific features, such as acid-
ity, swelling, ion-exchange properties, and a wide range of
preparation variables, and they can be used in catalysis, are
ease to workup, can be employed under mild experimental
conditions with good yield and/or selectivity, low cost, etc.
[19e21]. Several methods to obtain chemically modified
clays have recently been reported in the literature. This
chemical transformation gives rise to porous materials with
high specific surface areas, commonly known as PILCs
(pillared clays) and PCHs (porous clay heterostructures)
[22e29]. These modified clays have micro- and meso-
porosity and can then undergo further functionalization
using another amine-siloxane compound as the neutral
surfactant that provides a surface with a greater number of
positive charges to adsorb heteropolymetalates.
ꢀ
calcined at 550 C [29] (See Scheme 1).
2.2. PILC and PCH functionalization
PILC and PCH clay surfaces were further functionalized
with 3-aminopropyl-trimethoxysilane (F) to obtain an
adequate surface for the adsorption of the hetero-
polymetalate used as the active phase. Equal amounts of
water and ethanol were mixed with the clay under stirring
at room temperature for 24 h to activate the surface of the
aluminosilicate by generating silanol groups (SieOH).The
mixture was then cooled centrifuged and dried in an oven
In summary, the aim of the present work is the prepa-
ration and characterization of RhMo6 composites based on
Scheme 1. Preparation steps of bentonite-based systems, PILC and PCH.
Please cite this article in press as: G.R. Bertolini, et al., Composites based on modified clay assembled Rh(III)ehetero-
polymolybdates as catalysts in the liquid-phase hydrogenation of cinnamaldehyde, Comptes Rendus Chimie (2015), http://
dx.doi.org/10.1016/j.crci.2015.09.015

G.R. Bertolini et al. / C. R. Chimie xxx (2015) 1e10
3
at 70 ꢀC for 24 h to ensure the complete removal of solvent
and water. The functionalization of PILC and PCH was
conducted in a shaker at 70 ꢀC and 60 rpm for 12 h. Under
these conditions, the functionalization agent (F) and
toluene were used. Then, the materials were filtered and
washed in toluene and acetone to prevent hydration.
Finally, they were dried in an oven at 70 ꢀC for 24 h (See
Scheme 2).
Raman spectra were recorded at room temperature with
a Raman microprobe (Infinity from Jobin-Yvon) equipped
with a photodiode array detector. The exciting light source
was the 532 nm line of an Nd YAG laser and the resolution
of spectra was 2 cmꢁ1
.
XPS spectra were registered on a SPECS Multi-technique
analysis instrument spectrometer equipped with a dual X-
ray Mg/Al source and a PHOIBOS 150 hemispherical
analyzer in the mode of fixed analyzer transmission (FAT).
The spectra were obtained with a pass energy of 30 eV and
an Mg anode operated at 200 W. The pressure during the
measurement was lower than 2.10ꢁ8 mbar.
2.3. Composite preparation
The following composites: RhMo6/PCH, RhMo6/PCH-F
(on functionalized PCH), RhMo6/PILC and RhMo6/PILC-F
(on functionalized PILC) were prepared by equilibrium
adsorption impregnation in excess of pore volume on the
different supports using aqueous solutions of hetero-
polymolybdates (10 mg/mL of Mo) which were prepared
following previous studies of Mo adsorption isotherms on
alumina [15].
The sample was calcined in an oven at 150 ꢀC for 30 min,
then was pressed, placed on the sample holder of the in-
strument and evacuated to ultra-high vacuum for at least
2 h before the measurement. It was later reduced to 350 ꢀC
for 10 min in a H2-5%/Ar flow and evacuated to ultra-high
vacuum for at least 2 h before the second measurement.
The Rh3d, Mo3d, O1s, Si2p and Al2p regions were pro-
cessed by a computer. Electron binding energies were
referenced to the C1s peak at 284.6 eV. The intensity ratios
(for Rh or Mo) were obtained from peak area determination
by integration of the appropriate peak. To assess a quanti-
tative relationship between the XPS peak intensity ratio
and surface composition, the experimental results were
compared with the values predicted by the sensitivity
factor of Scofield [30].
2.4. Characterization of modified clays and their RhMo6
composites
The specific surface area, pore volume and pore diam-
eter were determined by the BET method, using Micro-
meritics ASAP 2020 equipment. The samples were
characterized by X-ray powder diffraction with a Philips
Temperature-programmed reduction (TPR) [15] used to
analyze the precursoresupport interaction was conducted
with Quantachrome equipment, Quantasorb Jr. model. The
reactor was fed with a10% H2/N2 mixture (flow ¼ 20 cm3/
min) and the temperature was raised from room temper-
PW 1714 diffractometer (Cu Ka radiation and Ni filter).
Thermogravimetric and differential thermal analysis
(TG-DSC) measurements were carried out using a Shi-
madzu thermoanalyzer (TGA-50 and DTA-50), at a heating
rate of 10 ꢀC/min, from room temperature up to 500 ꢀC in
air atmosphere. TG-DSC assays were performed using
10 mg of each sample.
Mo contents of the initial and final solutions were
determined by atomic absorption spectrometry (AAS),
using an IL-457 spectrometer. The concentration of Mo
adsorbed was then determined by mass balance [15].
Complementary chemical composition measurements
were made using scanning electron microscopy and
energy-dispersive X-ray spectroscopy (SEMeEDS) by
using a Philips SEM 505 microscope with a dispersive
energy system for microanalysis by using an X-ray, EDAX
9100.
ꢀ
ature to 850 C at a heating rate of 5 ꢀC/min.
To analyze the type of active site present on the surface
of the prepared materials, fresh composites were treated by
isopropanol adsorption followed by the temperature-
programmed surface reaction (TPSR). Thus, possible
acidic, basic and redox sites were determined [31e33].
Before being submitted to the test, the supports and com-
posites were heated at 350 ꢀC in 99.999% purity He for
30 min, and then, they were cooled to 40 ꢀC and 5 pulses of
isopropanol were injected. The solids were then heated to
350 ꢀC at a heating rate of 10 ꢀC/min and finally, the des-
orbed species were measured with a Balzers QMG 112 mass
spectrometer. The following masses were assigned: 44
(CO2), 41 (propene) and 43 (acetone).
2.5. Hydrogenation of cinnamaldehyde
Liquid-phase hydrogenation of cinnamaldehyde was
conducted in an Autoclave Engineers reactor at 10 atm H2
pressure and 85 ꢀC. A 0.20 g mass of the catalyst previously
reduced in flowing H2 at 350 ꢀC for 2 h, 0.8 mL of cinna-
maldehyde and 60 mL of toluene as solvent were used in
each test. The reaction progress was monitored by gas
chromatography
using
a
Varian
CP-3800
chromatograph equipped with a capillary column CP wax
52 CB (30 m ꢂ 0.53 mm) and a FID detector. Identification
of the reaction products was carried out in a GC/MS Shi-
madzu QP5050 mass spectrometer equipped with a capil-
lary column SUPELCO SPBTM-5 (30 m, 0.25 mm i.d.).
Scheme 2. Stages of functionalization of PILC and PCH systems.
Please cite this article in press as: G.R. Bertolini, et al., Composites based on modified clay assembled Rh(III)ehetero-
polymolybdates as catalysts in the liquid-phase hydrogenation of cinnamaldehyde, Comptes Rendus Chimie (2015), http://
dx.doi.org/10.1016/j.crci.2015.09.015

4
G.R. Bertolini et al. / C. R. Chimie xxx (2015) 1e10
3. Results and discussion
3.1. Physicochemical characterization of modified clays and
composites
Pillared clays are formed through a process that involves
the intercalation of inorganic cations ([Al13]), while to
obtain heterostructured clays a cationic surfactant and
neutral amine are intercalated between the clay layers.
Thus, a structural micelle with pillars of nanoscopic oxides
of Al(III) is produced in the PILC system. Regarding the PCH,
the subsequent addition of a siliceous (TEOS) precursor
causes an in situ polymerization of the silica pillars around
the micelle formed in the previous stage. Finally, these
inorganic or organic “templates” are removed by calcina-
tion at 550 ꢀC, producing materials with high specific sur-
face [23]. Thus, PILC and PCH materials of high surface area
are obtained (Table 1).
Additional functionalization of the materials (PILC and
PCH) was carried out with a unit of 3-amine-propyl-tri-
methoxysilane (F) to obtain a surface with a higher positive
charge to allow the adsorption of heteropolyanions. The
functionalization mechanism implies the interaction of a
unit of organosilane group with two silanols of the modi-
fied clay surface which produces a terminal amino group on
the surface according to the following equation [34]:
Fig. 1. (a) Comparative XRD of PILC (as prepared) and PILC-F (functionalized
sample) and (b) PCH (as prepared); PCH-F (functionalized sample) and PCH-
F treated at 300 ꢀC.
2SieOH þ SiðOMeÞ3ðCH2Þ3NH2/ðSiOÞ2SiðOMeÞðCH2Þ3NH2
þ 2MeeOH
by Dubinin, correspond to mesoporous materials [37].
However, the proportion of super-micropores for PCH was
also high [38,39].
Fig. 1(a) and 1(b) show the XRD diagrams of (a) PILC and
(b) PCH and their functionalized system, and PCH-F sample
treated at 300 ꢀC for 3 h with no noticeable structural
changes.
Figs. 2 and 3 show the results of the TGA profiles for the
PILC and PCH and TG-DSC for PILC-F and PCH-F systems.
Both PILC-F and PCH-F functionalized samples treated at
300 ꢀC undergo at least 5% more weight loss compared to
PILC and PCH, respectively. After functionalization, the sil-
icon content increases to at least 4 wt% for PILC-F and 6 wt%
for PCH-F, and the presence of new molecular units on the
surface also causes a large increase in weight and additional
adsorption of water molecules resulting in a greater weight
Once anchored to the channel walls, the organosilane
groups that possess donor amines can be used to prepare
polymetalates grafted to the clay modified surface.
Table 1 shows that the BET surface area is reduced
practically to 50% (for the PILC system) and to 20% (for the
PCH system) of the previous value, respectively. This fact is
probably due to the condensation reaction that is caused by
the functionalization process, where the amine groups
would produce electrostatic repulsions and the subsequent
reduction of the specific area. The functionalization cannot
completely eliminate the surface silanol groups, which
imparts a degree of hydrophilicity to the surface. This effect
is explained by the steric effect of the functionalizing agent.
This would act like an umbrella, protecting surface hy-
drated silanol groups and reducing the surface area [35,36].
The average pore diameter was 56 and 82 Å for PCH and
PCH-F, respectively, which, according to the classification
Table 1
Textural parameters and EDS chemical dataa of modified and functional-
ized clays.
Type of
clay
SBET
Pore volume Pore size Si %
Al %
Si/Al
(m2/g) (cm3/g)
BJH (Å)
Original
PILC
PILC-F
PCH
33
128
59
579
105
0.07
0.11
0.04
0.58
0.20
84
39
47
56
82
80.11 19.89
72.00 28.00
74.50 25.50
89.46 10.54
4.00
2.60
3.00
8.50
PCH-F
94.75
5.25 18.00
a
Data calculated from a content of Si þ Al ¼ 100%.
Fig. 2. TGA profile of PILC and PCH between room temperature and 500 ꢀC.
Please cite this article in press as: G.R. Bertolini, et al., Composites based on modified clay assembled Rh(III)ehetero-
polymolybdates as catalysts in the liquid-phase hydrogenation of cinnamaldehyde, Comptes Rendus Chimie (2015), http://
dx.doi.org/10.1016/j.crci.2015.09.015

G.R. Bertolini et al. / C. R. Chimie xxx (2015) 1e10
5
Fig. 3. A) TG-DSC of PILC-F and B) TG-DSC of PCH-F between room temperature and 500 ꢀC.
loss with increasing temperature. DSC profiles show an
endothermic signal around 100 ꢀC, corresponding to the
loss of hydration water, then the curve continues with a
negative slope without signals, suggesting slow loss of
molecular unities such as NH3 and CO2 and the subsequent
dehydroxylation at higher temperature.
These results are related to the data from SEM-EDS re-
ported in Table 1. Variations in the amounts of surface Al
and Si confirm the effect achieved by functionalization.
The equilibrium impregnation process of PILC and PCH
clays (untreated and functionalized) with RhMo6 solution
produced four composites. In these processes the hetero-
polyanion is adsorbed by ionic-par formation according to
the following surface reactions:
Fig. 4. Ideal representation of the electrostatic interaction between heter-
opolyanion RhMo6 and donor amines from organosilane groups from clay
surfaces.
PILC or PCH surface=3½≡SieOH2ꢃþ : ½RhMo6O24H6ꢃ
3ꢁ
þ3NH4ðOHÞ
pH. It should be noted that the support of alumina/silicate
may act as a pH buffer via the ionization of surface OH
groups (protonation or deprotonation) for a high ratio of
oxide/water used during impregnation [44]. In our case,
where Mo has a concentration of 10 mg/ml, one can easily
predict that protonation of basic surface OH groups will
lead to an increase of pH of the impregnation solution. This
pH increase in turn will lead to the partial
PILC ꢁ F or PCH ꢁ F surface=½ð≡SieOÞ SiðOMeÞ ðCH2Þ NH3ꢃþ
:
2
2
3
½RhMo6O24H6ꢃ3ꢁ þ 3NH4ðOHÞ
When PILC or PCH is immersed in RhMo6 aqueous so-
lution, the HPOM can be anchored onto the clay surface
mainly by electrostatic interactions [40]. The Anderson unit
contains three negative charges, which are neutralized in
the moderate acþid solution by protons in the form of acidic
þ
hydroxyl eOH2 or NH4 groups at the exterior of the
structure. In the normal pH range, proton adsorption on a
≡SieOH surface is very low. However, the presence of
moderately acidic heteropolyanions (pH ¼ 5) could mean
an increase in the proton adsorption reaction of ≡SieOH,
þ
forming a positively charged ≡eSieOH2 unit (on PILC or
þ
PCH surfaces) and eNH3 (on PILC-F or PCH-F surfaces)
[41]. Thus, HPOM clusters would assemble on the positively
charged surface forming anchored RhMo6 clusters [42,43].
Fig. 4 shows an ideal representation of the electrostatic
interaction between heteropolyanion RhMo6 and donor
amines from organosilane groups. However as it has been
well studied, during the process of impregnation using
solutions containing polymolybdates, Mo speciation may
occur leading to different oxyanions whose charge and size
depend on the pH. The kinetics of such reactions depend on
the Mo concentration of the starting solution and interface
Fig.
5. Comparative
Raman
microprobe
spectra
of
original
(NH4)3[RhMo6O24H6].7H2O (RhMo6) and the RhMo6/PCH-F composite
calcined at 200 ꢀC (spectral range 200e1200 cmꢁ1).
Please cite this article in press as: G.R. Bertolini, et al., Composites based on modified clay assembled Rh(III)ehetero-
polymolybdates as catalysts in the liquid-phase hydrogenation of cinnamaldehyde, Comptes Rendus Chimie (2015), http://
dx.doi.org/10.1016/j.crci.2015.09.015

6
G.R. Bertolini et al. / C. R. Chimie xxx (2015) 1e10
depolymerization of [RhMo6O24H6]3ꢁ with subsequent
2ꢁ
formation of nMoO4
.
The identification of molecular structures, such as
those of iso- and hetero-polyoxomolybdates character-
ized by MoeOeX and MoeOeMo bridges and terminal
MoeO bonds, can easily be accomplished by Raman spec-
troscopy [18].
Fig.
5 shows the comparative Raman Microprobe
spectra of the original RhMo6 ammonium salt and RhMo6/
PCH-F composite, which was the system with a higher
content of adsorbed RhMo6. The other systems based on
modified clays could not be characterized by this technique
because of the lower concentration of RhMo6, low intensity
lines and fluorescence under laser radiation, the typical
effect observed for aluminosilicates.
Fig. 6. EDS signals and SEM microphotograph of the RhMo6 sample
m). Semiquantitative analysis data in
element wt%: Mo: 84.09; Rh: 15.91. Theoretical values: wt%: Mo: 84.83;
Rh:15.16. Polyhedral representation of the heteropolyanion.
(magnification ꢂ500, scale bar ¼ 50
m
By comparing the Raman spectrum of the RhMo6 with
that of the RhMo6/PCH-F composite (previously heated at
200 ꢀC in air), it is evident that the interaction of the
Anderson phase with the support yielded band broadening
and shift to higher frequencies. In fact, the lines typical of
the Anderson structure are associated with the symmetric
stretching mode of terminal MoeO2t bonds at 949 cmꢁ1
and PCH. However, when the phase was supported on
either functionalized material, this percentage reached
7 wt% and 3 wt% for RhMo6/PCH-F and RhMo6/PILC-F,
respectively.
Table 2 shows data from the Mo chemical analysis by
AAS and EDS data of Mo, Rh, Si, Al and Fe for RhMo6/PILC/
PILC-F and RhMo6/PCH/PCH-F. Values for Si and Al agree
with the expected amounts for the final materials consid-
ering the additional incorporation of Al (for PILC) and Si (for
PCH or F-systems) during the respective chemical modifi-
cations undergone by the original clay.
Fig. 7 (a and b) show the EDS spectra of the function-
alized system (PCH-F) and the supported RhMo6 phase
(RhMo6/PCH-F), respectively. The lines of the major ele-
ments, Al and Si, are observed. Variation in the Si/Al ratio
was observed for the different samples because of the
treatment of the original material with silane-based sur-
factants and additional RhMo6 impregnation. Also, the
spectral lines corresponding to some typical original
metallic mineral ions (Ti, Mg, Fe) were observed. After
equilibrium impregnation with RhMo6 ammonium salt
aqueous solution, the material showed additional signals
corresponding to Mo and Rh of the heteropolyanion.
With regard to the values of Mo and Rh obtained by EDS,
the Rh/Mo ratio of about 0.3 wt% obtained duplicates the
ideal value of 0.17 wt%, suggesting the decomposition of the
structure, resulting in different oxo-anionic species of Rh
and Mo anchored to the surface. In order to investigate this
effect the XPS technique was used. This analysis provided
some insight into the chemical and dispersion degree of the
surface species both for the unsupported RhMo6 compound
and for the composite with a higher content of RhMo6,
RhMo6/PCH-F, which was previously treated at 150 ꢀC in an
(
(
ns) and the antisymmetric stretching at 889 and 852 cmꢁ1
nas). For the composite these lines merged at 970 cmꢁ1 for
ns and 949 cmꢁ1 for nas, respectively, indicating changes in
the structural symmetry and partial HPOM decomposition
with the subsequent formation of more compact poly-
oxoanions with a stronger Mo]O bond. The presence of
bands in the 900e960 cmꢁ1 region indicates the presence
of polymolybdic species on the surface of the support.
However, due to the large width of Raman bands observed
for supported Mo compounds, it is usually extremely
difficult to distinguish closely similar polyoxomolybdates.
Indeed, most of these species consist of edge-sharing
octahedra with a cis-dioxo structure (two short adjacent
terminal Mo]O bonds) that give rise to MoeO vibrations
(stretching or bending modes) in the same region [45].
Regarding the adsorption of the planar heteropolyanion
on g
- Al2O3 (Alþ3 rich surface), our studies of adsorption
isotherms indicated that in the first impregnation step, a
series of homogeneous and heterogeneous processes in
equilibrium occurred involving phase deposition and some
secondary reactions. These reactions, including the Al of
the support dissolution, counter diffusion and exchange of
cations [especially Rh(III) by Al(III)], have already been
characterized by spectroscopic and thermal methods
[17,18]. Then, the interaction between RhMo6 and Al(III)
ions on the surface of the aluminosilicate should not be
excluded, although the proportion of Al(III) at the clay
surface is always lower compared to that of Si.
In the present work, all RhMo6/clay composites ob-
tained were amorphous when observed with X-rays. No
peaks corresponding to RhMo6 were observed, which
means that the RhMo species must be well dispersed on the
surface.
Table 2
Chemical data of Mo% by AAS and major elements % by SEM-EDS for
RhMo6/PILC/PCH and RhMo6PILC-F/PCH-F systems.
Catalyst
Mo%
(AAS)
Mo%
(EDS)
Rh%
(EDS)
Si%
(EDS)
Al%
(EDS)
Fe%
(EDS)
Fig. 6 shows the SEM image of the sample, the EDS
spectrum, and the structural polyhedral representation
of the polyanion RhMo6 corresponding to the
(NH4)3RhMo6H6O24.7H2O salt.
RhMo6/PCH-F
RhMo6/PCH
RhMo6/PILC-F
RhMo6/PILC
7.00
1.30
2.00
1.00
18.07
2.30
1.10
2.20
6.18
0.86
0.25
0.80
65.65
81.13
69.92
67.25
4.49
10.30
23.46
24.55
5.61
5.41
5.27
5.20
The analysis by AAS revealed contents of approximately
1 wt% of Mo in the systems based on unfunctionalized PILC
*Data calculated based on the contents of major elements regardless of Mg
and light elements such as O, C or N.
Please cite this article in press as: G.R. Bertolini, et al., Composites based on modified clay assembled Rh(III)ehetero-
polymolybdates as catalysts in the liquid-phase hydrogenation of cinnamaldehyde, Comptes Rendus Chimie (2015), http://
dx.doi.org/10.1016/j.crci.2015.09.015

G.R. Bertolini et al. / C. R. Chimie xxx (2015) 1e10
7
energies that are characteristic of Rh(III) and Mo(VI),
respectively. However, in this case the Rh/Mo ratio derived
from the intensity ratio was much higher than the ideal
relationship, and also greater than the data obtained by
EDS (Table 3). This discrepancy indicates partial decom-
position of the Anderson phase structure, as it was
observed by Raman Microprobe studies.
XꢀPS data for the RhMo6/PCH-F composite (reduced at
350 C) revealed a Rh3d5/2 signal at 307.4 0.2 eV corre-
sponding to Rhꢀ and two Mo3d5/2 signals at 232.0 0.2 eV
and 229.1
0.2 eV corresponding to Mo(VI) and Moꢀ
respectively. These results confirmed the presence of Mo
from different polyanionic species, where more than 50% of
Mo is reduced. Taking into account our studies about the
reducibility of Mo in Anderson Phases [17], this result
indicated that the Mo content reduced at temperatures as
low as 350 ꢀC could belong to an Anderson polymolybdate
but the oxidized Mo content could belong to a species
molybdate with a lower degree of polymerization.
The behavior of RhMo6 in a reducing atmosphere (TPR)
as well as other isomorphic phases containing other het-
eroatoms (Co, Ni, Cu, Cr, etc.) has been widely investigated
in previous work at our laboratory [15]. Fig. 8 shows
comparative TPR diagrams corresponding to the original
RhMo6 phase and the same phase supported on both
modified materials. The profile of the pure phase (curve b)
displays an intense peak at around 285 ꢀC, and two signals
of lower intensity at approximately 370 and 707 ꢀC. The
first high signal includes the reduction of Rh (III) to Rhꢀ and
some Mo reduction steps, whose normal reduction stages
are as follows: Mo(VI)/Mo(IV)/Moꢀ [17]. By examining
the behavior of other Anderson phases containing different
Fig. 7. (a). EDS signals and microphotograph of the PCH-F sample (magni-
m). Semiquantitative EDS analysis data in
element wt %: Mg: 1.50; Al: 9.64; Si: 83.73; Ti: 0.78; Fe: 4.35. Total: 100. (b).
EDS signals and microphotograph of the RhMo6/PCH-F sample (magnifica-
fication ꢂ2500, scale bar ¼ 20
m
tion ꢂ2500, scale bar ¼ 20
mm).
inert atmosphere. Another measurement was performed
after “in situ” treating this sample at 350 ꢀC in a reducing
atmosphere, simulating the pretreatment to which the
sample is submitted before being used in the catalytic
reaction.
Data for the pure RhMo6 phase revealed a Rh3d5/2
signal at 310.8
0.2 eV and a Mo3d5/2 signal at
233.0 0.2 eV, corresponding to Rh(III) and Mo(VI),
respectively. Because of the overlapping of N1s with the
Mo3p3/2 component, the state and amount of N could not
be determined. The surface atomic composition nRh/
nMo ¼ 0.17, derived from the Rh/Mo intensity ratio [30], is
in excellent agreement with the bulk.
Data for the RhMo6/PCH-F composite (pre-treated at
150 ꢀC in an inert atmosphere) showed Rh3d5/2
Fig. 8. Diagrams of TPR corresponding to (a) RhMo6/PCH-F, (b) RhMo6
(309.6
0.2 eV) and Mo3d5/2 (232.1
0.2 eV) binding
original phase and (c) RhMo6/PILC-F.
Table 3
Binding energies (eV) and surface composition of pure RhMo6 and RhMo6/PCH-F (heated at 150 ꢀC and a reduced sample at 350 ꢀC).
Sample
Rh3d5/2 (eV)
Mo3d5/2 (eV)
Sample composition*
%MoS
%RhS
(nRh/nMo)S
(nRh/nMo)A
RhMo6
RhMo6/PCH-F
RhMo6/PCH-F(r)
310.8
309.6
307.4
233.0
232.1
0.17
0.56
0.53
0.17
0.34
0.34
4.6
1.9
2.1
2.6
2.1
232.2 (MoVI
)
229.1 (Moꢀ)
(r): pre-reduced sample; *S: XPS derived values; *A: data by SEM-EDS.
Please cite this article in press as: G.R. Bertolini, et al., Composites based on modified clay assembled Rh(III)ehetero-
polymolybdates as catalysts in the liquid-phase hydrogenation of cinnamaldehyde, Comptes Rendus Chimie (2015), http://
dx.doi.org/10.1016/j.crci.2015.09.015

8
G.R. Bertolini et al. / C. R. Chimie xxx (2015) 1e10
heteroatoms, it was found that the presence of metallic Rh
induces the complete reduction of Mo at lower tempera-
tures (~250 ꢀC). This effect can be observed both in the pure
phase and in the supported ones. The high reducibility of
RhMo6 can be associated with the oxidant character of the
noble metal.
alcohols, as is the case of IPA [47,48]. According to Scheme
3, the E1 mechanism of olefin formation involves one acid
site, on which a carbonium ion intermediate is formed; this
ionic species is then transformed into an olefin molecule.
For the E2 mechanism to be developed, both acid and basic
adjacent sites have to be present on the solid, leading to the
dehydration to either ether or olefin.
The TPR of the PCH-F-supported system (Fig. 8, curve a)
shows a strong signal centered at 235 ꢀC, corresponding to
the reduction of Rh, while the signals at 350 ꢀC and at
620 ꢀC are assigned to the reduction of Mo from different
oxide species which interact differently with the support. A
signal of low intensity at 540 ꢀC may be assigned to the
reduction of Fe belonging to the original clay. The tem-
perature values are slightly lower than those of the pure
phase (Fig. 8, curve b), though the signals are more intense;
this effect is caused by the interaction with the support
[18]. Regarding RhMo6/PILC-F (Fig. 8, curve c), due to the
low concentration of the supported phase, only one peak
was observed at approximately 200 ꢀC and corresponded to
species that interact weakly with the support. This signal
may be assigned to both Rh and primary Mo reduction
steps. The 2nd weak signal between 600 and 700 ꢀC cor-
responds to the Mo final reduction step. Such behavior
means that the Rh/Mo oxidic phases present different de-
grees of interaction according to their structural properties
and the support characteristics and suggests that for the
PCH-F support the HPOM interaction appears to be higher
due to a higher reduction temperature than for the RhMo6/
PILC-F system, which presented lower adsorbed Rh and Mo
concentration.
Fig. 9 reports the results of the TPSR analysis for the pure
PILC-F support and for the fresh RhMo6/PILC-F catalyst. No
desorption of propene was observed for the PILC-F support,
indicating an inactive surface toward IPA decomposition.
The deposit of the RhMo6 Anderson phase onto this support
incorporates Lewis acid sites to the surface. This fact ex-
plains desorption of propene observed. Regarding the PCH-F
support (Fig.10), the formation of propene with a maximum
at 110 ꢀC was detected. This result suggested the existence of
acid sites on the surface according to the E1 mechanism.
This fact has usually been reported for pure acidic solids,
such as silica-alumina and zeolites, [48] and could be
associated with higher values of specific area (Table 1). The
subsequent impregnation of these supports with RhMo6
heteropolyanion resulted in the addition of slightly stronger
new acid sites where propene was desorbed at higher
temperature,160 ꢀC (Figs.10 and 11). The presence of RhMo6
on both supports led to the desorption of propene at a
similar temperature, indicating sites of similar acid strength.
On the other hand, a small desorption band of CO2 at 100 ꢀC
was observed on RhMo6/PCH-F, implying the presence of
some basic sites in the system (Fig. 11). No desorption of
acetone was observed, indicating the absence of dehydro-
genation reactions in the studied systems.
The acid properties of the prepared supports and cata-
lysts were investigated by the method of isopropanol (IPA)
decomposition followed by TPSR. It is well known that the
dehydration of IPA on solid acids leads to the formation of
propene and 2-isopropyl ether, whereas its dehydrogena-
tion leads to the formation of acetone [46]. The dehydra-
tion/dehydrogenation selectivity depends, among other
factors, on the surface structure of the solid. The dehydra-
3.2. Catalytic evaluation
Scheme 4 shows the reaction for the hydrogenation of
cinnamaldehyde (CAL). The most important products ob-
tained from the hydrogenation of C]C bond and/or C]O
group/groups are cinnamic alcohol (CA), hydro-
cinnamaldehyde (HCAL) and hydrocinnamic alcohol or 3-
phenylpropanol (PP).
Fig. 12 shows the conversion attained by each of the
systems studied at 360 min of reaction. As can be seen, the
systems supported on PCH and PCH-F were found to be
€
tion reaction is the main process when strong Bronsted
(Hþ) and Lewis acid sites are present. The majority of pri-
mary alcohols react through an E2 concerted mechanism,
whereas an E1 mechanism can be found for secondary
Fig. 9. Desorption of propene as a function of temperature (TPSR), of the
Scheme 3. Isopropanol decomposition followed by TPSR.
PILC-F support and RhMo6/PILC-F catalyst.
Please cite this article in press as: G.R. Bertolini, et al., Composites based on modified clay assembled Rh(III)ehetero-
polymolybdates as catalysts in the liquid-phase hydrogenation of cinnamaldehyde, Comptes Rendus Chimie (2015), http://
dx.doi.org/10.1016/j.crci.2015.09.015

G.R. Bertolini et al. / C. R. Chimie xxx (2015) 1e10
9
Scheme 4. Reaction scheme of the cinnamaldehyde hydrogenation.
system due to the natural acidity of the support surface.
€
Thus a combined effect of Bronsted and Lewis acid sites
Fig. 10. Desorption of propene as a function of temperature (TPSR), of the
should not be discarded because the acidity of the support
PCH-F support and RhMo6/PCH-F catalyst.
has
a strong influence in this catalytic reaction, as
demonstrated recently in our work on RhMo6/alumina
supports of different surface acidity values [18]. Further
studies about these new catalysts are in progress to better
define their preparation and the reaction conditions.
more active than those supported on PILC and PILC-F,
whose activities were not higher than 5%. This result may
be attributed to the higher percentage of Rh and Mo found
on both PCH supports. Also, it is possible to observe that the
effect of functionalization on the PCH support led to an
increase in activity with respect to the unfunctionalized
system. Thus, after 360 min of reaction the conversion
obtained was 48% and 56% for RhMo6/PCH and RhMo6/
PCH-F, respectively. This effect may also be attributed to the
higher amount of Rh and Mo in the catalyst supported on
PCH-F. However, the increase in activity was lower than
expected, probably due to the fact that metallic ion sites
were not available enough for the reagent.
4. Conclusions
This study has shown that it was possible to obtain Rh-
Mo catalysts from the composites of Anderson-type het-
eropolymolybdates [RhMo6O24H6]3-and two types of het-
erostructured and functionalized Argentinean clays: PILC-F
and PCH-F. The functionalization process leads to a support
which is able to anchor polymetalate active phases and
provides an interesting approach in the field of immobi-
lized catalysts.
These materials, unlike other conventional catalysts,
combine the advantages of both heteropolycompounds and
clays such as, low cost, easy control of metal loading and
acidity levels.
These composites were evaluated in the liquid phase
hydrogenation of cinnamaldehyde. It was found that
RhMo6/PCH and RhMo6/PCH-F catalysts are more active
because of a higher concentration of heteropolyanions.
Prereduced catalysts led to a system where the hydroge-
nating capacity (Rh), the redox sites (Mo) and different
acid/base sites coexist to produce a good performance to
HCAL.
Table 4 shows the selectivities at 25% of conversion and
the different reaction products obtained for the most active
systems.
As can be seen, both PCH and PCH-F systems show a
good selectivity for the product (HCAL). The use of the
RhMo6/PCH-F catalyst strongly increased the selectivity to
HCAL and it showed similar selectivity to minority products
(PP and CA) compared with the same unfunctionalized
system. This behavior can be associated with Lewis acid
characteristics (shown in the study by TPSR) responsible for
the hydrogenation of the C]O group. The distribution of
minority products, CA and PP, showed by RhMo6/PCH-F can
be explained by acidic features provided by the hetero-
polyanion. This property increased for the functionalized
Fig. 12. Activity of the cinnamaldehyde hydrogenation at 360 min of reac-
Fig. 11. Desorption of CO2 for the RhMo6/PCH-F catalyst.
tion catalyzed by RhMo6/PCH, RhMo6/PCH-F, RhMo6/PILC and RhMo6/PILC-F.
Please cite this article in press as: G.R. Bertolini, et al., Composites based on modified clay assembled Rh(III)ehetero-
polymolybdates as catalysts in the liquid-phase hydrogenation of cinnamaldehyde, Comptes Rendus Chimie (2015), http://
dx.doi.org/10.1016/j.crci.2015.09.015

10
G.R. Bertolini et al. / C. R. Chimie xxx (2015) 1e10
~
Table 4
[16] C.I. Cabello, I.L. Botto, M. Munoz, H. Thomas, Stud. Surf. Sci. Catal 143
(2002) 565e573.
Selectivity of CAL hydrogenation to HCAL, PP and CA (at 25% of
conversion).
~
[17] C.I. Cabello, M. Munoz, I.L. Botto, E. Payen, Thermochim. Acta 447
(2006) 22e29.
Catalyst
SHCAL (%)
SPP(%)
SCA(%)
~
[18] G.R. Bertolini, C.I. Cabello, M. Munoz, M. Casella, D. Gazzoli, I. Pettiti,
G. Ferraris, J. Mol. Catal. A: Chem. 366 (2013) 109e115.
[19] F. Bergaya, G. Lagaly, General introduction: clays, clay minerals, and
clay science, in: F. Bergaya, B.K.G. Theng, G. Lagaly (Eds.), Handbook
of Clay Science: Developments in Clay Science, 1, Elsevier,
Amsterdam, 2006.
RhMo6/PCH
RhMo6/PCH-F
62
77
20
11
18
12
[20] Ch. Zhou, Appl. Clay Sci. 48 (1e2) (2010) 1e4.
[21] Ch. Zhou, Xn. Li, Zh. Ge, Qw. Li, Ds. Tong, Catal. Today 93 (5) (2004)
607e613.
Acknowledgements
[22] A. Gil, L. Gandía, M.A. Vicente, Catal. Rev.-Sci. Eng. 42 (2000)
145e212.
[23] A. Gil, S.A. Korili, M.A. Vicente, Catal. Rev.-Sci. Eng. 50 (2008)
153e221.
[24] T. An, J. Chen, G. Li, X. Ding, G. Sheng, J. Fu, B. Mai, K. O'Shea, Catal.
Today 139 (2008) 69e76.
[25] A. Elmchaouri, R. Mahboub, Colloids Surf. A 259 (2005) 135e141.
[26] J.Q. Jiang, C. Cooper, S. Ouki, Chemosphere 47 (2002) 711e716.
[27] J. Ma, L. Zhu, J. Hazard, J. Hazard. Mater. 136 (2006) 982e988.
[28] K.R. Srinivasan, S.H. Fogler, Clays Clay Miner. 38 (1990) 277e286.
We greatly appreciate the Prof. Edmond Payen’s coop-
ꢁ
eration allowing the use of Raman equipment at “Unite de
Catalyse et de Chimie du Solide”, UMR, CNRS France, and
for his valuable comments. We are grateful to Lic. Ma.
Fernanda Mori for their contribution in XPS measurements
and to Dr. Daniela Lick for TG-DSC measurements.
The authors would like to thank the following in-
stitutions for funding this work: ANPCyT for the purchase
of the SPECS multitechnique analysis instrument (PME8-
2003)”; (CONICET) (PIP 0185); CICPBA (Project 832/14) and
Universidad Nacional de La Plata (Projects X 633, X 700 and
I 172).
~
ꢀ
[29] M. Munoz, G. Sathicq, G. Romanelli, S. Hernandez, C.I. Cabello,
L. Botto, M. Capron, J. Porous Mater. 20 (2013) 65e73.
[30] C.D. Wagner, L.E. Davis, M.V. Zeller, J.A. Taylor, R.H. Raymond,
L.H. Gale, Surf. Interface Anal. 3 (1981) 211.
[31] M. Ai, S. Suzuki, J. Catal. 30 (1973) 362e371.
[32] M. Ai, Bull. Chem. Soc. Jpn. 50 (1977) 2579e2583.
[33] P. Mars, The Mechanism of Heterogeneous Catalysis, J. H. d. Boer,
Amsterdam, 1959, p. 49.
[34] D. Brunel, A. Cauvel, F. Fajula, F. Di Renzo, in: L. Bonneviot,
S. Kaliaguine (Eds.), Zeolites: A Refined Tool for Designing Catalytic
Sites, 1995, pp. 173e180.
References
[1] P. Gallezot, D. Richard, Catal. Rev. Sci. Eng. 40 (1998) 81e90.
[2] J. Kijenski, P. Winiarek, Appl. Catal. A: Gen. 193 (2000) L1eL4.
[3] F. Delbecq, P. Sautet, J. Catal. 152 (1995) 217e236.
[4] 4th ed., in: I. Kroschwitz (Ed.), Kirk-Othmer Encyclopedia of
Chemical Technology, vol. 6, Wiley, New York, 1992, p. 349.
[5] S. Narayanan, Bull. Cat. Soc. India 2 (2003) 107e116.
[6] A.M.C.F. Castelijns, J.M. Hogeweg, S.P.J.M. van Nispen, PCT Int. Appl.,
Patent WO 96/11898 Al (April 25, 1996) 14 p.
[35] A. Cauvel, D. Brunel, F. Di Renzo, P. Moreau, F. Fajula, in: H.K. Beyer,
H.G. Karge, I. Kiricsi, J.B. Nagy (Eds.), Catalysis by Microporous Ma-
terials, Studies in Surface Science and Catalysis, 94, 1995, pp.
286e292.
[36] J. Felipe Diaz, Kenneth J. Balkus Jr., Chem. Mater. 9 (1997) 61e67.
[37] M. Dubinin, Mat. Chem. Rev. 60 (1960) 235e238.
[38] A. Galarneau, A.T. Barodawalla, J. Pinnavaia, Nature 374 (1995)
529e531.
[7] A.M.C.F. Castelijns, J.M. Hogeweg, S.P.J.M. van Nispen, PCT Int. Appl.,
US Patent 5,811,588 (September 22, 1998) 6 p.
[8] A. Muller, J. Bowers, WO Patent WO 99/08989 (February 25, 1999)
to First Chemical Corporation.
[39] R.S. Murray, J.P. Quirk, Langmuir 6 (1990) 122e124.
[40] A.D. Newman, D.R. Brown, P. Siril, A.F. Lee, K. Wilson, Phys. Chem.
Chem. Phys. 8 (2006) 2893e2902.
[41] J. Lu, H. Tang, S. Lu, H. Wu, J.S. Piang, J. Mater. Chem. 21 (2011)
6668e6676.
[9] G.F. Santori, M.L. Casella, O.A. Ferretti, J. Mol. Catal. A: Chem. 186
(2002) 223e239.
[42] T. Blasco, A. Corma, A. Martinez, P. Martinez-Escolano, J. Catal. 177
(1998) 306e313.
€ €
[10] M. Lashdaf, A.O.I. Krause, M. Lindblad, M. Tiitta, T. Venalainen,
Appl.Catal. A: Gen. 241 (2003) 65e75.
[11] J. Breen, R. Burch, J. Gomez-Lopez, K. Griffin, M. Hayes, Appl. Cat. A:
Gen. 268 (2004) 267e274.
[43] G. Yadav, N. Asthana, V. Kamble, J. Catal. 217 (2003) 88e99.
[44] X. Carrier, J.F. Lambert, S. Kubab, H. Knozinger, M. Che, J. Mol. Struct.
€
656 (2003) 231e238.
[12] P. Reyes, C. Rodriguez, G. Pecchi, J.L. Fierro, Catal. Lett. 69 (2000)
27e32.
[45] M.T. Pope, Heteropoly and Isopolyoxometalates, Springer-Verlag,
Berlin, 1983.
[13] N. Mizuno, M. Misono, Chem. Rev. 98 (1998) 199e218.
[14] C.I. Cabello, I.L. Botto, H.J. Thomas, Appl. Catal. A 197 (2000) 79e86.
[15] C.I. Cabello, I.L. Botto, F. Cabrerizo, M. Gonzalez, H. Thomas, Adsorpt.
[46] A. Gervasini, J. Fenyvesi, A. Auroux, Catal. Lett. 43 (1997) 219e228.
[47] H. Knozinger, A. Scheglila, J. Catal. 17 (1970) 252.
[48] J.C. Luy, J.M. Parera, Appl. Catal. 26 (1986) 295.
ꢀ
Sci. Technol. 18 (7) (2000) 591e608.
Please cite this article in press as: G.R. Bertolini, et al., Composites based on modified clay assembled Rh(III)ehetero-
polymolybdates as catalysts in the liquid-phase hydrogenation of cinnamaldehyde, Comptes Rendus Chimie (2015), http://
dx.doi.org/10.1016/j.crci.2015.09.015