Catalytic oxidation of n-butanol over platinum supported mesoporous silica CMI-1

Article abstract of DOI:10.1016/j.molcata.2016.04.006

n-Butanol oxidation was studied using noble metals (Pt, Pd, Rh and Au) supported on a highly structured mesoporous material: CMI-1. The catalysts were characterized by several physico-chemical techniques, i.e. N₂ sorption, ICP, H₂ chemisorption, XRD and TEM. The Pt based catalyst was the most active material, followed by Pd/CMI-1, Rh/CMI-1 and Au/CMI-1. Difference in size of the particles was proposed as origin of these results, this parameter being well-known to strongly influence the catalytic activity. The comparison of two Pt/CMI-1 catalysts prepared from various precursor salts (with and without chlorine) showed that n-butanol oxidation was sensitive to the nature of the metallic salt. Finally the modifications induced by the nature of the support were studied by comparing Pt/Al₂O₃ and Pt/TiO₂ systems. Pt dispersion and specific surface area of the support seemed to be important parameters influencing the activity of the materials. In the studied conditions, Pt/CMI-1 was still the most active catalyst.

Full text of DOI:10.1016/j.molcata.2016.04.006

Accepted Manuscript
Title: Catalytic oxidation of n-butanol over platinum
supported mesoporous silica CMI-1
Author: Sma ¨ı n Sabour Catherine Especel C e´ line Fontaine
Mourad Bidaoui Lakhdar Benatallah Naima Saib-Bouchenafa
Jacques Barbier Jr Ourida Mohammedi
PII:
S1381-1169(16)30128-5
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.molcata.2016.04.006
MOLCAA 9850
To appear in:
Journal of Molecular Catalysis A: Chemical
Received date:
Revised date:
Accepted date:
4-3-2016
22-3-2016
9-4-2016
¨
Please cite this article as: Smain Sabour, Catherine Especel, C e´ line Fontaine,
Mourad Bidaoui, Lakhdar Benatallah, Naima Saib-Bouchenafa, Jacques
Barbier, Ourida Mohammedi, Catalytic oxidation of n-butanol over platinum
supported mesoporous silica CMI-1, Journal of Molecular Catalysis A: Chemical
http://dx.doi.org/10.1016/j.molcata.2016.04.006
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Catalytic oxidation of n-butanol over platinum supported mesoporous silica CMI-1
1
2*
2
3
1
Smaïn Sabour , Catherine Especel , Céline Fontaine , Mourad Bidaoui , Lakhdar Benatallah ,
1
2
1
Naima Saib-Bouchenafa , Jacques Barbier Jr , Ourida Mohammedi
1
Université Blida 1, Laboratoire de Chimie Physique Moléculaire et Macromoléculaire (LCPMM), BP270,
route Somaa, Blida, Algeria
2
Université de Poitiers, CNRS UMR 7285 IC2MP, Institut de Chimie des Milieux et des Matériaux de
Poitiers, 4 rue Michel Brunet, TSA 51106, 86073 Poitiers Cedex 9, France
3
Centre Universitaire de Tissemsilt, Institut des Sciences et Technologies, Abdelhak Benhamouda BP182,
Tissemsilt 38000, Algeria
*
Corresponding author:
Catherine Especel
catherine.especel@univ-poitiers.fr
Tel.: +33 5 49 45 39 94
1

Graphical abstract
2

Highlights





Total oxidation of n-butanol was studied on mesoporous silica-supported catalysts.
The conversion varied as follows according to the metallic phase: Pt > Pd > Rh > Au.
For the Pt/CMI-1 synthesis, the use of a Cl-based salt led to a less active sample.
The catalytic behavior of Pt catalysts supported on various supports was compared.
The Pt-based systems activity was governed by the support specific surface area.
3

Abstract
n-butanol oxidation was studied using noble metals (Pt, Pd, Rh and Au) supported on a highly
structured mesoporous material: CMI-1. The catalysts were characterized by several physico-
chemical techniques, i.e. N sorption, ICP, H chemisorption, XRD and TEM. The Pt based catalyst
2
2
was the most active material, followed by Pd/CMI-1, Rh/CMI-1 and Au/CMI-1. Difference in size of
the particles was proposed as origin of these results, this parameter being well-known to strongly
influence the catalytic activity. The comparison of two Pt/CMI-1 catalysts prepared from various
precursor salts (with and without chlorine) showed that n-butanol oxidation was sensitive to the
nature of the metallic salt. Finally the modifications induced by the nature of the support were
studied by comparing Pt/Al O and Pt/TiO systems. Pt dispersion and specific surface area of the
2
3
2
support seemed to be important parameters influencing the activity of the materials. In the studied
conditions, Pt/CMI-1 was still the most active catalyst.
Keywords
Mesoporous silica, CMI, Platinum, n-butanol, Oxidation.
4

1
. Introduction
Volatile organic compounds (VOC) contribute significantly to the air pollution by their toxic nature
and/or by the formation of photochemical smog [1,2]. As a result, research on VOC elimination has
attracted more interest over the last decade, with the development of efficient catalysts in VOC total
oxidation including precious metals and transition metals oxides [3,4]. Despite their expensive cost,
the noble metal catalysts are preferred due to their high activity, their resistance to deactivation and
their possible regeneration [2]. Catalytic performances of supported noble metals depend strongly on
the preparation method, the nature of the metallic precursor, the metal particle size, the metal content
and the nature of the support [5-7]. In addition, the nature of VOC, the operating conditions used
such as oxygen concentration and the global gas flow also have a noticeable influence on catalytic
performances [8,9].
Among noble metals cited in the literature, platinum and palladium are the most studied. Santos et al.
[
10] compared a series of noble metals supported on titania for the oxidation of three VOC, and
noticed that Au/TiO catalyst was the most active for the conversion of carbon monoxide, while in
2
the case of the ethanol and toluene oxidation the catalytic performances were ordered as follows:
Pt/TiO > Pd/TiO > Rh/TiO > Ir/TiO > Au/TiO . A similar study devoted to the formaldehyde
2
2
2
2
2
oxidation showed also the catalytic superiority of platinum- and palladium-based systems [11]. By
studying the catalytic oxidation of butanol, benzene and ethyl acetate, Papaefthimiou et al. [12]
concluded that catalysts containing platinum are generally more active than those with palladium.
Concerning the effect of the support nature, Peng et al. showed the efficiency of Pt/TiO systems for
2
formaldehyde oxidation compared to Pt-based catalysts involving other supports such as SiO or
2
CeO -ZrO mixed oxides [11]. These authors considered that the catalytic properties were not only
2
2
linked to the nature of the support but also to the metal dispersion. During the oxidation of ethyl
acetate on Pt-based catalysts, Papaefthimiou et al. [13] have highlighted the benefit influence of the
5

acidic properties of the support by comparing TiO and W-doped TiO displaying a higher density of
2
2
acid sites.
For some authors, the effect of the support hydrophobicity plays a decisive role in VOC oxidation.
Chuang et al. [14], by comparing the activities of Pt catalysts supported on hydrophobic and
hydrophilic materials, noticed that the oxidation can be achieved at low temperature on hydrophobic
supports. Similar results were obtained by Wu and Wang for the toluene oxidation on Pt catalysts
deposited on hydrophobic supports [15].
Some authors have recently reported the interest in using mesoporous silica materials as catalyst
supports for VOC oxidation [16-19], due to their high specific surface areas and pore volumes [20]
and their great thermal and mechanical stabilities [21]. In this context, this work is mainly dedicated
to the use of a specific silicic support highly structured (CMI-1, [22]) for n-butanol oxidation.
2
. Experimental part
2
.1. Catalysts preparation
The CMI-1 silica was synthesized according to the protocol described by Leonard et al. [23], using
decaoxyethylene cetyl ether [C16(EO)10, Brij 56®], tetramethoxysilane (TMOS, 98%) and sulfuric
acid (H SO , 98%).The synthesis of mesoporous alumina was performed by dissolution of 7.5 g of
2
4
Pluronic® (P123, PEO PPO PEO ) in 150 mL of ethanol with 11 mL of HNO (70%), under
2
0
70
20
3
stirring at room temperature. After the complete dissolution of P123, 30.75 g of aluminum
isopropoxide was added and the mixture was kept under stirring for 5 h, and further dried in an oven
-1
at 60°C. The gel obtained is calcined under air at 600°C (1°C.min ) during 6 h. TiO support
2
(99.9%) was provided by Alfa Aesar.
Pt/CMI-1, Pd/CMI-1, Rh/CMI-1 and Au/CMI-1 catalysts with a 0.5 wt% expected metallic content
were prepared from H PtCl (Aldrich), PdCl (Aldrich), Rh(NO ) (Aldrich) and HAuCl (Fisher)
2
6
2
3 2
4
precursor solutions, respectively. The precursor solution was dissolved in 50 mL of ultrapure water,
6

the pH was further adjusted to 2 (or between 8 and 9 in the case of Au-based catalyst) and then the
CMI-1 support was added. The solution was kept under stirring at room temperature for 2 h, and the
excess of solvent was removed by evaporation in a sand bath overnight. The samples were calcined
-1
under air at 300°C (1°C.min ) for 3 h.
Pt(acac)/CMI-1, Pt(acac)/Al O and Pt(acac)/TiO catalysts were also prepared using platinum
2
3
2
acetylacetonate precursor dissolved in 25 mL of toluene (Aldrich, 99.8%). After elimination of the
solvent by rotary evaporator, the solid was dried at 120°C overnight and then calcined under air at
-1
4
00°C (1°C.min ) during 3 h to ensure the total elimination of toluene.
2
.2. Catalysts characterization
The metal content of the catalysts was determined by ICP-OES (Inductively Coupled Plasma Optical
Emission Spectrometer) on a Perkin-Elmer Optima 2000 device.
Physical properties of the materials (specific surface area, average pore size distribution and pore
volume) were obtained from N -sorption isotherms collected at -196°C on a Micromeritics Tristar
2
3
000 apparatus. Samples were previously degassed for one night at 250°C until a residual pressure
below 0.15 mbar. The specific surface area was determined from the linear part of the BET plot, the
mesopore size distribution by the NLDFT (non local density functional theory) method and using the
Autosorb-1 1.52 software. The kernel selected was N on silica assuming cylindrical pore geometry
2
and the equilibrium based on the desorption branch. Pore volume was determined on the isotherms at
P/P = 0.97.
0
The characterizations by powder X-ray diffraction (XRD) were performed on a diffractometer
PANalytical Empyrean equipped with a copper anode as X-ray source (CuK radiation, λ = 1.54186
Å). The patterns were recorded for 2 comprised between 0.75° and 5° with a step of 0.01° (step
time of 10 s) and between 10° and 70° with a step of 0.05° (step time of 2 s). Phase identification
was made by comparison with JCPDS database. The lattice parameter (a ) of the structure
0
7

corresponding to the sum of the pore internal diameter and the thickness of the silica wall was
calculated from the relation a = (2/√3).d , with d issued from by Bragg formula 2d100 sinθ = nλ.
0
100
100
The size distribution of metal particles in the mesoporous structure was measured by Transmission
Electron Microscopy (TEM) on a JEOL 2100 UHR device (LaB source, 200 kV) equipped with a
6
Gatan Ultra scan camera. The samples were embedded in a polymeric resin (spur), cut into small
sections (50 nm) with an ultramicrotome equipped with a diamond knife, and then deposited on a Cu
grid holey carbon film. Average particle size of each analyzed sample was determined by measuring
at least 100 particles, from at least 5 different micrographs.
Hydrogen chemisorption was performed to determine metal dispersion by using a classical pulsed
-1
technique. After reduction of the sample under H (1.8 L.h , 1 h, 300°C), the reactor was flushed by
2
-1
Ar flow (1.8 L.h ) at the same temperature for 2 h before being cooled down to ambient temperature.
H pulses (0.25 mL) were injected at regular intervals, and the dispersion values were calculated by
2
assuming an H/surface metal atom stoichiometry equal to 1. From the amount of H consumed, the
2
average particle size was calculated using the equation as described elsewhere [24].
2
.3. Catalytic test of n-butanol oxidation
Experiments were performed according to the protocol established by Sedjame et al. [25]. The
gaseous feed used for the catalytic tests was composed of 1000 ppm of VOC in synthetic air. VOC
and water were heated in two thermostated saturators. Nitrogen was bubbled through these saturators
and the outflow was mixed with the synthetic air. At the reactor inlet the gas stream was composed
of 19.38% of O , 77.52% of N , 3% of H O and 0.1% of VOC. Transfer lines were heated at 110°C
2
2
2
-1
to avoid any condensation. The total flow rate was kept constant for all experiments (70 mL min ).
Reactions were carried out in a tubular fixed bed reactor placed in an electrical furnace equipped
with a temperature programmer. A thermocouple was inserted in the reactor near the catalyst bed to
measure exactly the reaction temperature. A mass of 140 mg of catalyst mixed with 1 g of cordierite
8

-1
were used for the reactions. The space velocity was 60000 h . The reaction products were analyzed
by a Gas Chromatograph (Varian 490-GC) equipped with a thermal conductivity detector (TCD) and
two columns: a Porapak Q (PPQ) to analyze air and carbon dioxide and a CP sil-5CB to analyze
hydrocarbons (butanol, butanal, acetic acid...). Experiments were performed between 50 and 350°C
-1
and the temperature was increased linearly by 0.5°C min . The uncertainty on the results is about ±
1
°C.
3
. Results and discussion
3
.1. Characterization of the M/CMI-1 catalysts
Four 0.5 wt% M/CMI-1 samples (with M = Pt, Pd, Rh or Au) were first prepared using the CMI-1
support previously synthesized. The main physical and structural characteristics of the CMI-1
support and these catalysts (Table 1) showed that the prepared samples belonged to the family of
mesoporous solids, with a high specific surface area and a significant thickness of the walls (≥ 20 Å).
Table 1: Specific surface areas, pore volumes, average pore diameters, lattice parameters and
dispersions of CMI-1 supported catalysts
CMI-1
846
26.3
0.97
51.1
24.8
-
Pt/CMI-1 Pd/CMI-1 Rh/CMI-1 Au/CMI-1
2
-1
Specific surface area (m .g )
835
26.1
0.97
51.7
25.6
0.4
824
26.0
0.97
51.7
25.7
0.5
835
26.2
0.97
51.4
25.2
0.6
845
26.3
0.97
51.1
24.8
0.5
-
Pore diameter D (Å)
P
3
-1
Pore volume (cm .g )
Lattice parameter a (Å)
0
a
Wall thickness W (Å)
Metal content (wt.%)
b
Average metal particle size (Å)
Metal dispersion (%)
-
-
14 (13)
66
15
17
-
-
-
a
W = a - DP
0
b
Determined by TEM analysis (between bracket, value calculated from dispersion value)
N -sorption isotherm of the CMI-1 material (Fig. 1A) was of type IV according to the IUPAC
2
classification, which is consistent with the formation of organized mesoporous materials [26]. The
low angle X-ray powder diffraction pattern of the CMI-1 support (Fig. 2A) exhibited a very intense
peak as well as two other undefined peaks, corresponding to reflections on the (100), (110) and (200)
9

planes of a 2D hexagonal structure as observed by Ren et al. [20]. At large angles (Fig. 2B), the
CMI-1 sample displayed a wide diffraction peak of 2 ≈ 23° attributed to amorphous silica [27]. A
honeycomb network with a hexagonal pore arrangement was clearly confirmed for the CMI-1
material by TEM analysis (Fig. 3A).
Fig. 1. N -sorption isotherms of CMI-1 (A) and Al O (B) synthesized supports.
2
2
3












20

 50


70
0
.5
1.5
2.5
3.5
4.5
5.5
10
30
40
60
2
theta (°)
2 theta (°)
Fig. 2. X-ray diffraction patterns: (A) small angle of the CMI-1 support and (B) wide angle of the Pt-
based catalysts (prepared from Pt acetylacetonate precursor salt).

: Pt phase;  anatase phase;

rutile phase
10

A
B
Fig. 3. TEM images of (A) CMI support and (B) 0.5 wt% Pt/CMI-1.
As showed in Table 1, after impregnation of the CMI-1 support by metals (deposited content of 0.5 
0
.1 wt% according to the experimental values determined by ICP-OES), each catalyst displayed a
2
-1
high specific surface area in the same range of order than that of the lone support (835  10 m .g ).
3
-1
Moreover, the pore volume (0.97 cm .g ) and pore diameter (D = 26.15  0.15 Å), as well as the
P
lattice parameter (a = 51.4  0.3 Å) and wall thickness (W = 25.25  0.45 Å), remained unchanged
0
after the metal impregnation on the CMI-1 support indicating that the deposition of the metal
(whatever its nature) did not affect the structure of the mesoporous oxide. On Fig. 3B showing a
TEM representative image of the Pt/CMI-1 catalyst, the metallic particles appear well dispersed. The
analysis by TEM of the Pd/CMI-1 and Rh/CMI-1 catalysts (images not shown) led to the same
observation, whereas no detection of Au particles was possible indicating that the particles of the
Au/CMI-1 sample are too small for the microscope resolution. From TEM images, average particle
sizes of 14 Å, 15 Å and 17 Å were estimated for the Pt/CMI-1, Pd/CMI-1 and Rh/CMI-1 catalysts,
respectively. In the case of the Pt/CMI-1 sample, this average size is in accordance with the one
determined from the metal dispersion value (Table 1). In fact, from hydrogen chemisorption
experiments, the Pt phase dispersion was estimated to 66% which corresponds to an average particle
size of 13 Å [24], i.e. very slightly lower than that calculated by TEM. The difference can be
explained by the existence of small particles not observed by TEM analysis.
11

3
.2. Catalytic transformation of n-butanol on the M/CMI-1 catalysts
.2.1. Effect of the presence of steam
3
A preliminary test of n-butanol oxidation was performed on the Pd/CMI-1 catalyst in presence and
absence of water steam in the gas feed. The plots of n-butanol conversion to CO obtained for each
2
experiment (Fig. 4) clearly show that there is no effect of steam on the oxidation reaction with these
catalysts. Conversely, a recent study dealing with Pt/Al O catalysts showed the inhibiting effect of
2
3
steam on the oxidative removal of the n-butyl alcohol [25]. Consequently, the present result
highlights the interest of using support displaying hydrophobic sites for VOC oxidation reactions
[
28,29]. Indeed, mesoporous silica-based materials such as CMI-1 possess different groups on their
surface, including silanols (Si-OH) and siloxanes (Si-O-Si) [30]. Siloxanes are considered to be
hydrophobic sites generated by dehydroxylation during heat treatment [28,29], while the silanol
groups are considered as weak acid sites [31]. In order to stay as close as possible to the real
conditions, water steam has been added to the feed for the experiments performed in the rest of the
manuscript.
Fig. 4. CO yield during n-butanol transformation on Pd/CMI-1: influence of the presence ( ) and

2
absence ( ) of steam in the gas feed.

3
.2.2. Effect of the nature of the metal
12

The behavior of the four M/CMI-1 (M = Pt, Pd, Rh or Au) catalysts was evaluated for the oxidation
of n-butanol conducted in the presence of steam (Fig. 5). The activities of the materials are compared
in term of light-off, i.e. the temperature necessary to convert 50% (T ) or 90% (T ) of the reactant:
5
0
90
the lower is the T or T , the more active is the catalyst. Following this criteria, the activity of the
50
90
different catalysts for the total conversion to CO was classified as follows: Pt/CMI-1 > Pd/CMI-1 >
2
Rh/CMI-1 > Au/CMI-1. The Au/CMI-1 catalyst led to the lowest conversion of n-butanol (T =
5
0
2
57°C and T90 > 300°C for 50% and 90% conversion, respectively). By comparison, the T50
temperature observed for the Rh/CMI-1 sample was quite similar (254°C) but the T was lowered to
9
0
2
87°C. The presence of Pd on the CMI-1 support involved a noticeable improvement of the activity
since 50% and 90% of conversions were obtained at 207 and 214°C, respectively. Finally, with the
Pt/CMI-1 sample, a new decrease approximately of 23°C was achieved for the T temperature (T =
5
0
50
1
84°C), a lower one being observed for T90 (T90 = 208°C). As seen previously, these CMI-1
supported catalysts exhibit a mesoporous structure with comparable high specific surface areas and
wall thicknesses allowing them to present a thermal stability [32]. The different activities observed
here are undeniably linked to the nature of the metal, since the metal particle sizes are not so
different for all M/CMI-1 catalysts (Table 1).
Fig. 5. CO yield during n-butanol transformation on M/CMI-1: Pt (

), Pd (
), Rh ( ), Au (-).

2
13

3
.2.3. Effect of the nature of the metallic precursor salt
As Pt/CMI-1 was the most active catalyst, we focused on this catalyst to study the influence of the
nature of the Pt precursor salt on its behavior during the catalytic oxidation of n-butanol. Two 0.5
wt% Pt/CMI-1 catalysts prepared from two precursor salts of platinum were compared (Fig. 6): the
previous sample Pt/CMI-1 synthesized from H PtCl and a new one Pt(acac)/CMI-1 issued from
2
6
platinum acetylacetonate impregnation (the characteristics of this sample are given in Table 2).
Table 2: Characteristics of the Pt(acac) catalysts supported on CMI-1, Al O and TiO
2
3
2
Pt(acac)/CMI-1 Pt(acac)/Al O3
Pt(acac)/TiO2
2
2
Specific surface area (m /g)
833
26
177
12
45
23
0.5
80
11
Pore diameter D (Å)
P
Pt content (wt.%)
Pt dispersion (%)
0.5
59
0.5
69
a
Average metal particle size (Å)
14
12
a
Value calculated from dispersion value
The comparison of the CO formation curves clearly showed that the Pt(acac)/CMI-1 catalyst was
2
the most active: by replacing the H PtCl precursor salt by the Pt acetylacetonate free-chlorinated
2
6
one, the T temperature decreased from 184°C to 130°C and the T value from 208°C to 191°C.
5
0
90
Since the textural properties were quite comparable for both samples (Tables 1 and 2), as well as the
average metal particles (13-14Å), the residual chlorides on the Pt/CMI-1 catalyst were supposed to
have a detrimental effect on the n-butanol conversion. It is well known that the preparation process
and the nature of the metal precursors used, such as chlorinated salts, can affect the properties of the
catalysts because the thermal treatment by calcination under air does not allow the complete removal
of the chloride ions [33]. Even if catalysts prepared from chloride salts often present a higher metal
dispersion, their catalytic activity can be lower than previously observed for example for the
complete oxidation of propene and toluene on Pt/γ-Al O catalysts prepared by impregnation from
2
3
either Pt(NH ) (OH) or H PtCl solution [5,7,34]. The detrimental effect of chloride was explained
3
4
2
2
6
by a partial blockage of the active metal sites involving a decrease of their ability to activate the
14

reagent molecules [34,35]. In addition, the formation of less active M O Cl oxochlorinated species
x
y
z
was also mentioned [5,36,37].
Fig. 6. CO yield during n-butanol transformation on Pt/CMI-1(

) and Pt(acac)/CMI-1 ( ).

2
3
.2.4. Effect of the nature of the support
From the Pt acetylacetonate precursor salt, two other catalysts Pt(acac)/Al O and Pt(acac)/TiO
2
2
3
were prepared by varying the nature of the support and compared with the Pt(acac)/CMI-1 sample
Table 2). The Pt(acac)/Al O sample prepared from the synthesized alumina support displayed a
(
2
3
2
-1
much lower specific surface area than the one of Pt(acac)/CMI-1 (177 compared to 833 m .g ), this
2
-1
surface reached 45 m .g for the Pt(acac)/TiO catalyst prepared form the commercial titania. After
2
the deposit of 0.5 wt.% Pt, the metal dispersion was measured by XRD and the average particle size
was evaluated to 14, 12 and 11 Å on the CMI-1, Al O and TiO supports, respectively. The presence
2
3
2
of diffraction peaks located at 2 = 40°, 46° and 68° and attributed to platinum phase was detected
on these three catalysts, as well as a mixture of anatase and rutile phases in the case of the sample
supported on titania (Fig. 2B).
Fig. 7 compares the CO yield obtained as function of the temperature during the conversion of n-
2
butanol on the three Pt(acac) supported catalysts. The T temperatures were quite comparable for
9
0
15

the three catalysts, but the T temperatures differed since 130°C, 158°C and 167°C were obtained
5
0
with CMI-1, Al O and TiO supports, respectively.
2
3
2
Fig. 7. CO yield during n-butanol transformation on Pt(acac) catalysts supported on:
2
CMI-1 (

), Al O (

), TiO2 ( ).

2
3
The three studied catalysts were prepared by impregnation of the same chlorine-free precursor salt,
consequently no residual chlorine species can affect the catalytic behavior. The metallic phase was
not dispersed similarly on the various supports, but the Pt(acac)/CMI-1 catalyst with the highest
average particle size was finally the most active sample. Several authors related that the dispersion of
the active phase is an important factor on the catalytic performances, the metal particle size decrease
involving generally a positive effect on the catalytic activity [38-40]. Consequently, the results of
Fig. 7 indicate that the parameter explaining the different activities of the three studied catalysts was
first the nature of the support. The catalyst supported on CMI-1 presents a large specific surface area
which can provide an important contact with n-butanol.
4
. Conclusions
The following conclusions can be drawn from this study devoted to the catalytic oxidation of n-
butanol on metallic supported catalysts:
16

-
the use of mesoporous CMI-1 support with hydrophobic sites seemed to limit the inhibitory effect
of water during VOC oxidation,
among the studied metals (Pt, Pd, Rh and Au), the Pt-based catalyst was the most active for the
catalytic oxidation of n-butanol,
the use of a chlorinated precursor for the preparation of Pt/CMI-1 catalysts induced an inhibiting
effect on their activity for n-butanol conversion,
the catalytic activity of supported Pt-based catalysts for n-butanol conversion was governed by the
-
-
-
specific surface area of the support.
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