Synthesis and catalytic performance in the propene epoxidation of a vanadium catalyst supported on mesoporous silica obtained with the aid of sucrose

Article abstract of DOI:10.1039/c6nj03632e

Mesoporous silica was prepared with the use of low-cost and environmentally friendly sucrose as a porogeneous agent. It was found that the presence of sucrose as well as the products of its chemical transformation upon the synthesis procedure (i.e., furfural polymer) affected markedly the structure and morphology of the resulting porous silica. The influences of the sucrose content and the source of the silicon as well as the synthesis conditions (pH, temperature) were very significant. The samples obtained in an acidic medium of the initial mixture formed from TEOS and treated at room temperature gave rise to products with a high surface area and narrow pore size distribution. Despite the lack of pore ordering, their catalytic activity in propene epoxidation after vanadium modification was remarkable in comparison to the activity of the vanadium catalyst supported on ordered mesoporous materials.

Full text of DOI:10.1039/c6nj03632e

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ISSN 1144-0546
PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
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Synthesis and catalytic performance in propene epoxidation of
vanadium catalyst supported on mesoporous silica obtained with
aid of sucrose
Received 00th January 20xx,
Accepted 00th January 20xx
Ewa Janiszewska*, Stanislaw Kowalak
DOI: 10.1039/x0xx00000x
The mesoporous silica was prepared with aid of low-cost and environmentally friendly sucrose as porogeneous agent. It
was found that the presence of sucrose as well as the products of its chemical transformation upon the synthesis
procedure (i.e. furfural polymer) affected markedly the structure and morphology of the resulting porous silica. The
influence of sucrose content, source of silicon as well as synthesis conditions (pH, temperature) was very significant. The
samples obtained in acidic medium of initial mixture formed from TEOS and treated at room temperature gave rise to the
products with high surface area and narrow pore size distribution. Despite the lack of pore ordering, their catalytic activity
in propene epoxidation after vanadium modification was remarkable in comparison to the activity of vanadium catalyst
supported on ordered mesoporous materials.
www.rsc.org/
carbohydrates as porogeneous agents. The mesoporous silicas
were mostly obtained by sol-gel method in the presence of
optically active organic compounds (D-glucose, dibenzoyl-L-
tartaric, D-maltose)19 or hydroxy-carboxylic acids (citric, lactic,
Introduction
Mesoporous ordered materials prepared by surfactant
templated hydrothermal method were first reported in 1992
by Mobil1,2 and Toyota3 research groups. High surface area and
ordered, uniform pore size (2-50 nm) of this type of materials
made them very important group of molecular sieves.
Investigations on synthesis and properties of the mesoporous
molecular sieves still develop enormously due to the potential
application of such materials as catalysts, catalyst supports,
absorbents and host materials.4-6 The great variety of chemical
compositions of mesoporous molecular sieves includes also
carbon tubes or metallic materials.4 A large number of various
porogeneous materials are applied for syntheses. The ionic5-7
or neutral8-10 surfactants, have been mostly used as templates
in early syntheses of mesoporous materials. Then the di- and
triblock copolymers become common and efficient
porogeneous agents.11-13 Many other materials such as
supramolecular aggregates of small molecules14, hard
templates15,16 or even biological matrices, such as virus liquid
crystals17 or plant cellular structures18 are employed.
Sometimes the price of the auxiliary reagents is very high and
usually they are not recovered after completed syntheses.
Therefore searching for efficient but much less expensive
porogeneous materials is still challenging. The saccharides
could be considered worthwhile to check in synthesis
procedure of mesoporous materials. There are already some
literature reports on synthesis of mesoporous silica with aid of
malic and tartaric acids)20 in acidic medium. The synthesis with
sucrose as a porogeneous agent, however, was carried out in
basic medium.21 It is assumed that synthesis of porous silica
with these type of porogeneous agents involves a hydrogen
bonding between the carbohydrate molecules and silanol
groups of silica precursor (N°I° mechanism) which initiates and
directs the formation of mesostructure. Syntheses were
carried out by mixing carbohydrate solution with silicon source
and maintaining the resulted sol at room temperature to allow
a slow evaporation of solvent (for 20 days- 2 months). The
mesoporous silica with high specific surface areas and narrow
pore size distribution were obtained after removing the
templates by washing or Soxhlet extraction (optically active
organic compounds, hydroxy-carboxylic acids) or calcination in
air (sucrose). The main drawback of these type of synthesis is
their long time. Saccharides were also use in synthesis of
hierarchical materials (AlPO-5, AlPO-11, TS-1)22,23 to generate
mesopores. They were also used as an auxiliary agents in
synthesis of ordered mesoporous SBA-1 to enhance
hydrothermal stability.24,25
The conditions of the aforementioned synthesis procedures
did not affect noticeably the structure of applied sucrose. It
was interesting for us to check if some chemical
transformation of sucrose upon the hydrothermal preparation
of mesoporous silica could favorably influence the morphology
of the resulting porous products. Hydrothermal synthesis in
acidic or basic environment can cause a hydrolysis of
carbohydrate with subsequent transformations of step
products towards polymeric products. The latter may play a
a.Adam Mickiewicz University, Faculty of Chemistry, Umultowska 89b, 61614
Poznan, Poland, E-mail: eszym@amu.edu.pl
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role of template in assembling of the mesoporous structure. It other oligosacccharides undergoes a hydrolysis in acidic
is conceivable that obtained porous structure as well as medium to form respective monosccharides. The latter can
chemical nature of the surface could be influenced by this undergo further degradation to heterocyclic aldehydes
approach. The resulting properties could be reflected in an (furfurals), which readily polymerize and form long chain
improved efficiency of the catalysts prepared with silica molecules, suitable for assembling an inorganic material upon
support prepared according to the presented procedure.
its condensation. Many earlier studies have indicated that
The ordered mesoporous materials are very often used for several factors (e.g., temperature, pH, the surfactant/silica
heterogenization of homogeneous catalysts in order to ratio, ions present in the synthesis mixture) could affect the
combine the advantages of heterogeneous catalyst such as interaction between organic micelles and inorganic species
easier product – catalyst separation with the advantages of and consequently influence the final structure of the
homogeneous catalysts, e.g. higher selectivity26-28 as well as a mesoporous materials during the self-assembly process.45 As
supports for noble metal or metal oxides catalysts.29,30 the furfural’s polymers are different type of template then
Vanadium oxides supported on mesoporous silica have conventional neutral templates used for preparing
received much attention because of their catalytic properties. mesoporous materials (e.g. Pluronics) their interaction with
They exhibit high activity and selectivity for a number of silica may differ. For this reason the influence of source of
reactions, such as the partial oxidation of methane,31,32 silicon, sucrose content, synthesis conditions (pH,
methanol oxidation to formaldehyde,33,34 and the oxidative temperature) on properties of obtained silica samples were
dehydrogenation of short-chain alkanes towards the examined. The chosen samples of prepared series with good
production of the respective alkenes.35-38 The study on textural properties (i.e. high surface area, narrow pore size
oxidative dehydrogenation of propane showed that the unique distribution) were used as a support for vanadium catalyst.
textural properties of these supports allow to obtain very Their catalytic ability in transformation of propene to PO with
effective and selective catalysts. High surface area of N2O as an oxidant was evaluated.
mesoporous silica allows on better dispersion of metals even
at relatively high loadings, compared to classical non-porous or
low-surface area oxide supports.35,38 Liu et al.38 evidenced that
not only high surface area, but also appropriate structure, pore
diameters or even acidity of silica mesoporous materials
influence the efficiency of obtained catalysts.
Experimental
Synthesis
Water glass (WG, Na2O/SiO2/H2O= 15.25/30/54.75 in wt%,
Vitrosilicon, Poland) and tetraethoxysilane (TEOS, Aldrich) were the
principal sources of silicon applied for syntheses. Sucrose (POCh,
Poland) was used as porogeneous agent (PA). The pH of the gel was
adjusted in the range of 1-12 by adding adequate amounts of
aqueous ammonia (POCh, Poland) or hydrochloric acid (POCh,
Poland). In a typical synthesis the solution of sucrose (40 % wt.) was
mixed with solution containing silicon source. The pH of the mixture
was then adjusted to the chosen value. The mixture was stirred at
room temperature for 2 hours and then heated (if necessary) in the
temperature range 298- 443 K for 20 hours. The resulting products
were filtered, washed with distilled water, dried and calcined in air
(723-973 K) to remove the organic components.
Propylene oxide (PO) is an important intermediate in
production of many fine chemicals. PO is industrially produced
by means of two main processes: the chlorohydrin process and
by method that involves organic peroxides. Both processes
suffer from serious drawbacks, therefore, searching for new
cleaner, more convenient and safer technologies is still
challenging. Reviews about different approaches are given by
Oyama,39 Nijhuis40 or Cavani et al.41 Although presented
developments are scientifically significant, they suffered from
either low PO selectivities, low propylene conversions, or short
catalyst lifetimes or they required the use of higher pressures
or costly co-reactants. Much attention was paid to propylene
epoxidation with H2O2 over TS-1 (MFI) catalyst.39,41,42 The
process involving H2O2 was commercialized, however, because
of the high price of H2O2, the profitability of this process is still
an open question.41 A new perspective in propene epoxidation
process became viable when N2O was found an efficient
oxidant along with catalyst based on iron species supported on
silica matrices. Epoxidation of propene with N2O over the iron
oxide supported on silica and promoted with Na ions attained
a propene conversion ~5-10% at 648 K with selectivity towards
PO ~50%.43 It was also shown that various ordered,
mesoporous silica materials modified with vanadium species
were capable of transforming propene to propylene oxide with
N2O oxidant. The best results of the investigated series were
obtained with catalysts prepared by impregnation of silica
SBA-3 with vanadium ions.44
The support with SBA-3 structure was synthesized as a benchmark
matrix for the vanadium catalysts. It was obtained according to the
literature description with cetyltrimethylammonium bromide
(CTABr, Aldrich) and tetraethylorthosilicate (TEOS, Aldrich) as
principal reagents.46
Characterization
The products were characterized by means of standard methods.
The characterization procedures comprised the calcined samples as
well as those right after hydrothermal syntheses. X-ray diffraction
(XRD) patterns were collected using
a Bruker D8 Advance
diffractometer with Cu-Kα radiation (λ=1.54056 Å). The Fourier
transform infrared spectra (KBr) were recorded with Bruker Vector
22 spectrophotometer. Transmission electron microscope (TEM)
images were taken using HRTEM with JEOL ARM 200F operating at
200 kV. The thermal behaviour of the samples was followed by
thermogravimetric and differential thermal analyses (TG and DTA)
Here, we present a novel approach to synthesis of mesoporous
silica with aid of sucrose by hydrothermal method. Sucrose as
2 | J. Name., 2012, 00, 1-3
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in air (with heating rate of 10 °C/min) using SETARAM SETSYS 12 medium (at RT and elevated temperatures) as a band at ca. 1700
equipment. The BET surface area and pore parameters of the cm-1 (C=O band) which disappears after calcination (Fig.1A). This
samples were determined by nitrogen adsorption-desorption band is seen both in spectrum of as-synthesized samples as well in
isotherm measurements at 77 K on a Micromeritics ASAP 2000 washed samples what suggests that water insoluble furfural
sorptometer. The samples were outgassed at 573 K prior to the polymer is a prevailing organic material embedded in resulted
measurement. Total pore volume and average pore radius were porous silica. If monomeric furfural were present in samples, the
determined by the Barrett-Joyner-Halenda (BJH) method. UV-vis band at 1700 cm-1 vanished on washing (solubility of furfural in
diffuse reflectance spectra of vanadium modified samples were water is 83 g/l).
recorded at room temperature on a Cary 100 UV-vis spectrometer
0
(Varian) in the range of 190-900 nm. Prior to measurement, the
samples were diluted with the pure silica (SiO2, POCh, Poland) with
the weight ratio of 1:100 and then were dehydrated by calcination
for 1 h at 673 K. The spectrum of silica support was subtracted as
the baseline for each catalyst.
A
pH=1, calcined
B
15
30
45
60
75
90
pH=8, washed
pH=1, washed
pH=1, washed
pH=1
pH=8, washed
pH=8
Catalyst preparation and catalytic studies
pH=1, as synthesized
1705
Chosen samples were modified with vanadium ions by means of
incipient wetness impregnation, using the aqueous solutions of
VOSO4 ·5H2O (in amount related to 3 wt.% of V). After impregnation
and drying (373 K) the catalysts were calcined in air at 823 K for 1 h.
The catalytic tests for propene oxidation were performed in
continuous flow reactor. Catalytic experiments were carried out at
0
200
400
600
800
1900
1400
900
400
Wavenumber [cm-1]
Temperature [oC]
Fig. 1. FTIR spectra (A) and weight loss (TG) (B) for samples synthesized at
indicated pH (water glass, PA/Si=1.69, 368 K).
The formation of insoluble furfural polymer was confirmed by
thermal analysis (TG). The weight loss on calcination of the samples
synthesized in acidic medium is high (ca. 80 %). Very similar weight
loss is seen for the as-synthesized samples after their washing.
Samples obtained at almost neutral pH show low weigh loss (ca. 5
%) after washing which suggests that water soluble organic
compounds (i.e. furfural) can be removed from the products (Fig.
1B). It is reflected in vanishing of the band at 1700 cm-1 in FTIR
spectrum of the samples synthesized at pH=8 after washing.
653 K, under atmospheric pressure, with WHSV = 3420 ml/h/gcat
,
related to contact time of 1.1 s. Prior the measurements, the
catalysts were heated in helium flow at 723 K for 30 min.
Substrates: propene and N2O were diluted with helium (molar ratio
of propene: nitrous oxide: helium = 1 : 15 : 12.5). The products were
analyzed using on-line GC, equipped with FID and TCD detectors.
The catalytic performance was expressed as conversion (%),
selectivity (%) and yield (%) calculated as described elsewhere.44
The catalytic activity of the samples was compared with the activity
of vanadium catalyst supported on conventional silica SBA-3. SBA-3
silica was already studied in our laboratory as matrix of the
vanadium catalyst for propylene epoxidation and was found the
most promising silica support among several other under study.44
The thermal analysis of the samples indicate two distinct steps in
weight loss on heating (TG curves) (Fig. 2). The first one (up to ca.
300 °C) results from removal of water which is consistent with
respective endothermic effect (DTA curves). The next significant
weight loss (200 - 600 °C) is due to the organic compounds
0
15
30
45
60
75
90
0
10
20
30
40
50
60
70
80
Results and discussion
A
B
Synthesis
DTA
TG
Syntheses in basic medium (pH=12) of initial mixture allow to obtain
only small amount of the solid product. Much higher yield was
obtained in syntheses conducted at lower pH (8 or particularly 1). It
is well known, that the silica precursor can form different species
under different pH. When the syntheses are performed in basic
medium the stable dimeric silicic species should exist in a solution
which only weakly interact with the template and do not
polymerize to form a continuous regular network.45
DTA
TG
30 130 230 330 430 530 630 730
30 130 230 330 430 530 630 730
Temperature [oC]
Temperature [oC]
0
1
2
3
4
5
6
C
It was interesting to notice that the synthesis in acidic medium
DTA
TG
(pH=1) causes
a formation of dense dark brown jelly. The
transparent jelly was formed from almost neutral (pH=8) mixtures
on heating as well as from acidic mixtures at ambient temperature
(RT). Brown color of the samples obtained in acidic medium at
elevated temperature was caused by condensation of furfural
formed during hydrolysis of sucrose and its subsequent
transformation. The presence of furfural or the product of its
polymerization is seen in FTIR spectra of samples obtained in acidic
30 130 230 330 430 530 630 730
Temperature [oC]
Fig. 2. TG and DTA analyses of washed samples synthesized under indicated
conditions: water glass, PA/Si=1.69, 368 K (pH=1 (A), pH=8 (C)); TEOS,
PA/Si=0.56, pH=1, 368 K (B).
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nature of the samples under study. The low-angle powder XRD
patterns show only a shoulder (small intensity broad peak) that can
indicate some, but rather poor ordering of mesopores in short
range (Fig. 3). The samples obtained with low amount of saccharide
or at higher pH do not show even this shoulder.
TEM micrographs confirm a lack of long-range order in the pore
structures. However, for some samples interconnected wormlike
pores (Fig. 4) with disordered arrangements are displayed in the
images.48 The TEM images of presented samples look similar as
those prepared with contribution of sucrose and presented in
literature.19,47,48
Fig. 3. Low angle XRD patterns of samples obtained with different source of
silica: A - water glass (pH=1, 368 K, PA/Si=0.38 (a), PA/Si=0.56 (b),
PA/Si=1.69 (c); pH=8, 368 K, PA/Si=1.69 (d) ), B – TEOS (pH=1, PA/Si=0.56,
298 K (a), 368 K (b), 443 K (c)).
decomposition. The DTA curves show an exo- and endothermic
effects in this region which can originate from oxidation of organic
compound and desorption of oxidation products, respectively. In
the case of samples obtained from TEOS the additional exo- and
endothermic effects in the temperature range of 250 - 450 °C are
observed. This can be attributed to oxidation and desorption of
some not completely reacted TEOS (remaining ethoxy groups)47 or
from compounds that might be generated from ethanol and furfural
derivatives upon the synthesis. The washed samples formed at pH ~
8 indicate low weight loss during the calcination and it takes place
within the whole investigated temperature range. The predominant
endothermic effect on DTA curve (at ~ 100 °C) results from
desorption of adsorbed water. The further weight loss is probably
caused by dehydration of silanol groups. Contrary to the above
samples (Fig. 2A and B) there are no evidences of any thermal
effects on the DTA curve due to a decomposition or transformation
of organic remnants.
Fig. 4. TEM micrographs of samples obtained from water glass (A, B: pH=1,
Ordering of the pore system in the samples
PA/Si=1.69, 368 K) and TEOS (C, D: pH=1, PA/Si=0.56, 368 K).
XRD patterns in the high angle region (6-60°) of all samples (not
shown) indicate only a broad halo at 2Θ value of ~23° that
corresponds to amorphous silica and confirms an amorphous
Table.1. Textural properties of chosen samples.
Sample
number
Si source
PA/Si
initial pH of
synthesis
temp. of synthesis
[K]
surf. area
[m2/g]
mean pore
diam. [nm]
pore volume
[cm3/g]
1
2
water glass
water glass
water glass
water glass
TEOS
0.38
0.56
1.69
1.69
0.56
0.56
1.69
1.69
0.56
0.56
1
1
1
8
1
8
1
1
1
1
368
368
368
368
368
368
298
443
298
443
431
524
599
230
607
177
559
381
808
247
7.5
5.0
0.81
0.66
0.72
1.03
0.61
0.84
0.49
1.20
0.60
1.08
3
4.8
4
17.9
4.0
5
6
TEOS
19.1
3.5
7
water glass
water glass
TEOS
8
12.6
3.0
9
10
TEOS
17.6
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Textural characterization
pressure region from 0.4 to 0.8 implies framework mesoporosity.49
The sample obtained with the lowest amount of sucrose shows an
isotherm with a steep rise in adsorbed volume at relative pressure
p/p0˃0.8, corresponding to relatively larger pore size (above 10 nm)
and broader pore size distributions (3 to 30 nm) than other
samples. According to the literature, the hysteresis loop at high
partial pressure (p/p0˃0.8) is indicative of textural mesoporosity
and/or macroporosity, whereas the sharp increase in nitrogen
The obtained samples exhibit IV-type adsorption-desorption
isotherms. This type of isotherm always indicates the presence of
mesopores in obtained samples. The surface area value and pore
size distribution depend markedly on the syntheses parameters
(Table 1). In general, an increase in sucrose content (in respect to
silicon) in initial mixture results in increasing BET surface area
(sample 1, 2, 3). Such correlation was also observed for the
mesoporous materials prepared with aid of nonsurfactant
templates.19-21 Moreover, the increase in the template
concentration results in the reduced average pore size (Fig. 5A). The
latter is in contrast to previously observed correlations.19,20 The
pore size distribution becomes also more uniform with increasing
amount of sucrose. Samples synthesized with higher amount of
sucrose show narrow pore size distribution in a range from 2 to 9
nm and similar isotherms with a steep rise in adsorbed volume at
relative pressure p/p0˃0.4. The hysteresis loop in the partial
uptake at p/p0˃0.9 is indicative of
a significant amount of
interparticle mesoporosity.49 Therefore, the porosity of this sample
most likely arises from voids formed between the aggregated
particles. These results indicate that the presence of a certain
amount of sucrose in the initial gel is important for the formation of
uniform mesoporous structure. Too low content of sugar in the
mixture causes that only a limited amount of the silicon participates
in inorganic-organic assembling process which results in a low
surface area.
0.3
700
0.3
600
A
B
0.2
600
0.2
500
0.1
500
0.1
400
400
0
0
0
10
20
30
40
50
0
10
20
30
40
50
Pore diameter [nm]
Pore diameter [nm]
300
200
100
0
300
200
100
0
0,38PA : 1Si
0,56PA : 1Si
1,69PA : 1Si
pH=1
pH=8
0
0.2
0.4
0.6
0.8
1
0
0.2
0.4
0.6
0.8
1
Relative pressure (P/P0)
Relative pressure (P/P0)
0.4
600
500
400
300
200
100
0
0.5
0.4
0.3
0.2
0.1
0
700
D
298K
368K
443K
C
0.3
0.2
0.1
0
600
500
400
300
200
100
0
0
10
20
30
40
50
0
10
20
30
40
50
Pore diameter [nm]
Pore diameter [nm]
water glass
TEOS
0
0,2
0,4
0,6
0,8
1
0
0,2
0,4
0,6
0,8
1
Relative pressure (P/P0)
Relative pressure (P/P0)
Fig. 5. N2 adsorption-desorption isotherms and pore size distribution for samples synthesized: A - with different concentration of sucrose (water glass, pH=1,
368 K), B - at different pH (water glass, PA/Si=1.69, 368 K), C - with different source of silicon (PA/Si=0.56, pH=1, 368 K), D - at different temperatures (TEOS,
PA/Si=0.56, pH=1).
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Lowering the pH of the initial mixture (sample 3, 4 and 5, 6) results and pore volume is only a result of existing the silica interparticle
in higher surface area, lower average pore size and more narrow porosity.
pore size distribution in resulted samples (Fig. 5B). Increase in
Catalytic properties
nitrogen uptake at p/p0˃0.9 for samples obtained at higher pH
indicates only the presence of interparticle mesoporosity. Usually
changing in the textural properties of materials with increase of the
pH of synthesis mixture were explained by changing the formation
mechanism and rate of hydrolysis and polymerization of the
inorganic source.45,50 The absence of the framework porosity in the
presented synthesis at higher pH could rather results from the fact
that furfural polymer is not formed and monomeric furfural formed
in these conditions is unable to form mesopores in the silica
framework. The broadening of the pore size distribution at higher
pH of the synthesis mixture is in line with previously reported
results, which used different surfactants and silica precursors.45,50-52
The chosen samples with the best textural properties (samples no.
9 and 5 obtained in acidic medium with TEOS as a silicon source at
298 and 368 K) were applied for accommodation of vanadium
species and employed as catalyst for propene epoxidation with N2O
as an oxidant. The samples differ slightly in surface area and pore
diameter what can influence the distribution and kind of formed
vanadium species on their surface.
Surface area and pore volume of vanadium impregnated materials
decreased in comparison to unmodified samples, whereas the pore
diameters did not change (Table 2). It indicates, that the formed
vanadium species are located only inside the pores or on the
surface.
It is caused by increasing silica dissolution
– reprecipitation
processes that take place with increasing pH values and also the
weaker interactions between oligomeric silicic species and the
template.
Table 2. Textural properties of supports and catalysts.
Sample
temp. of
synthesis
[K]
surf. area
[m2/g]
mean pore
diam.
[nm]
2.1
pore
volume
[cm3/g]
0.74
Syntheses with TEOS instead of water glass (sample 2 and 5) under
the same conditions (the same pH, temperature, molar ratio PA/Si)
led to the products with higher surface area and narrower pore size
distribution (Fig. 5C). According to the literature data inorganic
species (e.g. Na+) present in synthesis mixture can interact with
surfactants and change specific interaction between surfactant and
silica species improving the properties of the obtained materials
(better ordering, shape of crystals, etc.) or lowering the
temperature of synthesis.53,54 Using a cheap sodium silicate instead
of TEOS for the synthesis of SBA materials does not affect the
formation of well-ordered samples with good textural
properties.55,56 In our case, sodium cations present in water glass
can change the mechanism of mesoporous silica formation for less
favorable. Probably the interactions template - silica are weaker
than in the case if TEOS is used as a silica source. Similar
observation was also reported by Léonard et al.45
SBA-3
3V/SBA-3
9
3V/9
5
298
1432
1144
808
2.0
0.56
298
368
3.0
3.0
0.60
0.50
663
607
4.0
0.61
3V/5
522
4.1
0.54
Regardless of silica source, lowering the temperature of synthesis
seems beneficial for getting high porosity of the products (sample 7,
3, 8 or 9, 5, 10). Samples obtained at room temperature indicate a
higher surface area, relatively small average pore size and the
narrower pore size distribution than those prepared at elevated
temperatures (Fig. 5D). A steep rise in adsorbed volume is shifted to
higher value of relative pressure p/p0 and the contribution of
framework mesoporosity decrease with increasing temperature of
synthesis. The higher temperature favors also a formation of less
uniform pore size distribution and increased pore size. Similar
observation are reported in literature for mesoporous materials
obtained in the presence of neutral surfactants.51,57 It is caused by
increased radius of micelles51 or weakened H-bonds between the
surfactant head groups and the neutral inorganic precursor species
with increasing temperature of synthesis.57 Decrease in the
framework porosity and its lack for the samples synthesized at
443K, observed in the presented results, suggests that the
condensation of silica at this temperature is too fast in comparison
to the rate of furfural resin formation and it takes place practically
without participation of template. The increasing pore size value
Fig. 6. Propylene conversion, selectivity to PO and PO yield (top) and
selectivity towards all products (bottom) on indicated samples at 653 K (PO -
propylene oxide, AP – propionaldehyde, AC – acetone + acrolein, COx – CO +
CO2).
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Fig. 7. UV – vis reflectance spectra of diluted samples of vanadium catalysts supported on silica obtained at 298K (A), 368 K (B) and SBA-3 (C).
Table 3. Results of the UV-vis spectra data for the vanadium modified (similar as V modified SBA-3 material) which is in contrast to the
samples.
sample obtained at elevated temperature (Table 3). According to
literature data44 this type of vanadium species are responsible for
catalytic activity in propene epoxidation. It explains the higher
activity of the sample obtained at room temperature. The obtained
results indicate that higher surface area (sample obtained at 298 K)
provides the better distribution of vanadium moieties and
formation of mostly isolated V5+ species, efficient in catalytic
reaction. A formation of higher amount of bigger vanadium species
on the sample obtained at elevated temperature can be caused by
lower surface area in comparison to surface area of that
synthesized at 298 K. The V catalyst based on silica support
synthesized at 298 K shows lower activity than this obtained with
SBA-3 support, despite of the same nature of the V sites (isolated
monomeric VOx). The reason of lower activity may result from its
larger pores (3.0 nm) in comparison to pores of SBA-3 support (2.0
nm). Such observation was done also by Pérez-Ramírez et al.59 The
authors examined the catalytic activity of microporous Fe-silicalite
and mesoporous Fe-SBA-15 with very similar amount, nature,
distribution and red-ox properties of extra framework iron species.
They indicated that the large pores in SBA-15 do not generate the
required intimate contact between potentially active Fe sites and
reactant molecules and most of the latter passing the pore system
of mesoporous silica without approaching the active sites. Perhaps
in the case of our catalyst with larger pores (prepared with
contribution of furfural) its lower activity compared to the narrower
SBA-3 also results from retarded contact of reagents with vanadium
active sites. The lowest activity of the catalyst with support
prepared at elevated temperature can be caused not only by lower
number of the active V monomers but also by limited contact with
them in even larger pore system (4.0 nm).
Sample
temp. of
UV-vis band
Area of
VOx structure
synthesis position [eV] absorption
[K]
band
4.93
5.81
4.13
4.93
5.80
3.61
3.99
4.90
5.80
0.2624
0.0714
0.0024
0.2619
0.0652
0.0084
0.0358
0.2980
0.0734
Td, mono +oligo
Td, mono
3V/SBA-3
3V/9
298
Td, oligo
298
368
Td, mono +oligo
Td, mono
Td, oligo
Td, oligo
3V/5
Td, mono +oligo
Td, mono
The vanadium modified samples show activity for propylene
epoxidation (Fig. 6). Besides the desired propylene oxide several
other oxidation products mainly including propionaldehyde,
acetone, acrolein, COx are always found in the reaction products.
Vanadium modified samples obtained on support synthesized at
room temperature show noticeable propene conversion and PO
yield in comparison to the activity of V catalyst supported on SBA-3
silica. The catalyst obtained from silica sample synthesized at
elevated temperature exhibits much lower activity in the studied
reaction. The significant differences observed in the activity and the
selectivity to PO result from different kind of vanadium species
formed on the surface of used materials. UV-vis spectra recorded
for the catalysts diluted with SiO2 and dehydrated exhibit
absorption bands at 4.0, 4.9 and 5.8 eV (Fig. 7). These bands are
attributed to the ligand to metal charge-transfers (CT) of Td-
coordinated V5+ species. The band at 5.8 eV is assigned to highly
dispersed, monomeric tetrahedrally coordinated VOx species. The
additional band at 4.0 eV is attributed to oligomeric tetrahedral VOx
groups linked in the chains by V-O-V bridges. The band at 4.9 eV is
common for both isolated monomeric and oligomeric tetrahedrally
coordinated VOx species.58 The band assigned to Td oligomers for
the samples obtained at elevated temperature is divided into two
bands (at 3.99 and 3.61 eV), probably due to the different length of
oligomeric V5+ species. This sample exhibits also a higher amount of
oligomeric tetrahedral V5+ species in comparison to the samples
obtained at 298 K (Table 3). The sample obtained at 298 K shows
almost exclusively the isolated V5+ species in tetrahedral position
Conclusions
The presented results indicate that sucrose can be used as an
efficient porogeneous agent for preparation of porous silica.
The interaction of sucrose with silicon precursors by means of
hydrogen bonds suggested in earlier works19,21 is very likely.
However, the most spectacular influence of sucrose on
properties of resulted porous silica was noticed in acidic
medium which facilitated a hydrolysis of disaccharide, and,
moreover, it initiated transformation to furfural with
subsequent polymerization. It is likely that formed polymer
chains interact with silicic acid and result in assembling the
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Journal Name
15 R. Ryoo, S.H. Joo and S. Jun, J. Phys. Chem. B, 1999, 103
7743-7746.
16 F. Schüth, Angew. Chem. Int. Ed., 2003, 42, 3604-3622.
17 C.E. Fowler, W. Shenton, G. Stubbs and S. Mann, Adv.
Mater., 2001, 13, 1266-1269.
18 Y. Shin, J. Liu, J.H. Chang, Z. Nie and G.J. Exarhos, Adv.
Mater., 2001, 13, 728-732.
19 Y. Wei, D. Jin, T. Ding, W.-H. Shih, X. Liu, S.Z.D. Cheng and Q.
Fu, Adv. Mater., 1998, 4, 313-316.
20 J.-B. Pang, K.-Y. Qiu, Y. Wie, X.-J. Lei and Z.-F. Liu, Chem.
Commun., 2000, 477-478.
,
silica tetrahedra upon their condensation around the furfural
polymer matrix. Such an action of furfural polymers could be
responsible for the formation of silica porous materials with
high surface area and relatively narrow mesopore size
distribution. Similarly as in reported syntheses of porous silica
with aid of saccharose21, the obtained samples do not exhibit
pore ordering always noticed for typical M41S or SBA
materials. The presented preparation procedure is not energy
and time-consuming (room temperature, 20 hours) and
regarding very low cost of sucrose (contrary to conventional
templates) can gain a practical meaning. It is likely that further
optimization of syntheses may lead to the products with
tailored porous structure and desired nature of the surface.
The vanadium modified samples show a noticeable activity and
selectivity in propylene epoxidation and it is possible that
further study could bring more promising results.
21 D.-W. Lee, Ch.-Y. Yu and K.-H. Lee, J. Mater. Chem., 2009, 19
299-304.
,
22 X. Yang, T. Lu, Ch. Chen, L. Zhou, F. Wang, Y. Su and J. Xu,
Micropor. Mesopor. Mat., 2011, 144, 176-182.
23 W. Wang, G. Li, L. Liu and Y. Chen, Micropor. Mesopor. Mat.,
2013, 179, 165–171.
24 Ch.-Ch. Ting, H.-Y. Wu, Y.-Ch. Pan, S. Vetrivel, G.T.K. Fey and
H.-M. Kao, J. Phys. Chem. C, 2010, 114, 19322-19330.
25 H.-M. Kao, Ch.-Ch. Ting, A.S.T. Chiang, Ch.-Ch. Teng and Ch.-
H. Chen, Chem. Commun., 2005, 1058-1060.
26 A. Corma and H. Garcia, Chem. Rev., 2002, 102, 3837-3892.
27 D.E. De Vos, M. Dams, B.F. Sels and P.A. Jacobs, Chem. Rev.,
2002, 102, 3615-3640.
28 S. Koner, K. Chaudhari, T.K. Das and S. Sivasanker, J. Mol.
Catal. A-Chem., 1999, 150, 295-297.
Acknowledgements
This work was supported by National Science Centre (grant no.
N N204 119238). The authors thank Dr. A. Held (Faculty of
Chemistry, Adam Mickiewicz University, Poznan) for catalytic
activity examination and Dr. Grzegorz Nowaczyk
29 D. T. On, D. Desplantier-Giscard, C. Danumah and S.
Kaliaguine, Appl. Catal. A-Gen., 2003, 253, 545–602.
(NanoBioMedical Centre, Adam Mickiewicz University, Poznan) 30 A. Taguchi and F. Schüth, Micropor. Mesopor. Mater., 2005,
77, 1-45.
for the HR-TEM measurements.
31 H. Berndt, A. Martin, A. Brückner, E. Schreier, D. Müller, H.
Kosslick, G.-U. Wolf and B. Lücke, J. Catal., 2000, 191, 384–
400.
32 L.D. Nguyen, S. Loridant, H. Launay, A. Pigamo, J.L. Dubois
and J.M.M. Millet, J. Catal., 2006, 237, 38–48.
33 M. Baltes, K. Cassiers, P. Van Der Voort, B.M. Weckhuysen,
R.A. Schoonheydt and E.F. Vansant, J. Catal., 2001, 197, 160–
171.
References
1
C.T. Kresge, M.E. Leonowicz, W.J. Roth, J.C. Vartuli and J.S.
Beck, Nature, 1992, 359, 710-712.
2
J.S. Beck, J.C. Vartuli, W.J. Roth, M.E. Leonowicz, C.T. Kresge,
K.D. Schmitt, C.T.-W. Chu, D.H. Olson, E.W. Sheppard, S.B.
McCullen, J.B. Higgins and J.L. Schlenker, J. Am. Chem. Soc.,
1992, 114, 10834-10843.
34 M. Baltes, P. Van Der Voort, O. Collart and E.F. Vansant, J.
Porous Mat., 1998, 5, 317–324.
35 S.A. Karakoulia, K.S. Triantafyllidis and A.A. Lemonidou,
Micropor. Mesopor. Mater., 2008, 110, 157–166.
36 L. Čapek, J. Adam, T. Grygar, R. Bulánek, L. Vradman, G.
Košová-Kučerová, P. Čičmanec and P. Knotek, Appl. Catal. A-
Gen., 2008, 342, 99–106.
3
4
T. Yanagisawa, T. Shimizu, K. Kuroda and C. Kato, Bull. Chem.
Soc. Jpn., 1990, 63, 988-992.
R. Xu, W. Pang, J. Yu, Q. Huo and J. Chen, Chemistry of
Zeolites and Related Porous Materials: Synthesis and
Structure; J. Wiley & Sons (Asia) Pte LTD, Singapore, 2007.
A.D. Firouzi, D. Kumar, L.M. Bull, T. Besier, P. Sieger, Q. Huo,
S.A. Walker, J.A. Zasadzinski, C. Glinka, J. Nicol, D. Margolese,
G.D. Stucky and B.F. Chmelka, Science, 1995, 267, 1138-
1143.
Q. Huo, R. Leon, P.M. Petroff and G.D. Stucky, Science, 1995,
268, 1324-1327.
D. Danino, Y. Talmon and R. Zana, Langmuir, 1995, 11, 1448-
1456.
37 R. Zhou, Y. Cao, S. Yan, J. Deng, Y. Liao and B. Hong, Catal.
Lett., 2001, 75, 107–112.
5
38 Y.-M. Liu, W.-L. Feng, T.-Ch. Li, H.-Y. He, W.-L. Dai, W. Huang,
Y. Cao and K.-N. Fan, J. Catal., 2006, 239, 125–136.
39 S.T. Oyama, in: S.T. Oyama (Ed.), Mechanisms in
Homogeneous and Heterogeneous Epoxidation, Elsevier,
Amsterdam, 2008, pp. 1–99.
40 T. A. Nijhuis, M. Makkee, Jacob A. Moulijn and B. M.
Weckhuysen, Ind. Eng. Chem. Res., 2006, 45, 3447-3459.
41 F. Cavani and J. H. Teles, ChemSusChem, 2009, 2, 508-534.
6
7
8
9
P.T. Tanev, M. Chibwe and T.J. Pinnavaia, Nature, 1994, 368
321-323.
,
42 Q. Wang, L. Wang, J. Chen, Y. Wu and Z. Mi, J. Mol. Catal. A:
Chem., 2007, 273, 73-80.
S.A. Bagshaw, E. Prouzet and T.J. Pinnavaia, Science, 1995,
269, 1242-1244.
43 V. Duma and D. Hönicke, J. Catal., 2000, 191, 93-104.
44 A. Held , J. Kowalska-Kuś and K. Nowińska, Catal. Commun.,
2012, 17, 108-113.
45 A. Léonard, J.L. Blin, P.A. Jacobs, P. Grange and B.L. Su,
Micropor. Mesopor. Mat., 2003, 63, 59–73.
46 O.A. Anunziata, A.R. Beltramone, M.L. Martínez and L.L.
Belon, J. Colloid Interf. Sci., 2007, 315, 184–190.
47 I. Mukherjee, A. Mylonakis, Y. Guo, S.P. Samuel, S. Li, R.Y.
Wie, A. Kojtari and Y. Wie, Micropor. Mesopor. Mat., 2009,
122, 168-174.
10 W. Zhang, M. Froeba, J. Wang, P.T. Tanev, J. Wong and T.J.
Pinnavaia, J. Am. Chem. Soc., 1996, 118, 9164-9171.
11 D. Zhao, J. Feng, Q. Huo, N. Melosh, G.H. Fredrickson, B.F.
Chmelka and G.D. Stucky, Science, 1998, 279, 548-552.
12 D. Zhao, Q. Huo, J. Feng, B.F. Chmelka and G.D. Stucky, J. Am.
Chem. Soc., 1998, 120, 6024-6036.
13 G.D. Stucky, D. Zhao, P. Yang, W. Lukens, N. Melosh and B.F.
Chmelka, Stud. Surf. Sci. Catal., 1998, 117, 1-12.
14 S. Polarz, B. Smarsly, L. Bronstein and M. Antonietti, Angew.
Chem. Int. Edit., 2001, 40, 4417-4421.
8 | J. Name., 2012, 00, 1-3
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Please do not adjust margins
New Journal of Chemistry
Page 9 of 10
Journal Name
View Article Online
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ARTICLE
48 Y. Wie, J. Xu, H. Dong, J.H. Dong, K. Qiu and S.A. Jansen-
Varnum, Chem. Mater., 1999, 11, 2023-2029.
49 J.M. Campelo, D. Luna, R. Luque, J.M. Marinas, A.A. Romero,
J.J. Calvino and M.P. Rodríguez-Luque, J. Catal., 2005, 230
327–338.
50 C.J. Brinker, J. Non-Cryst. Solids, 1988, 100, 31-50.
,
51 G. Herrier, J.L. Blin and B.L. Su, Langmuir, 2001, 17, 4422-
4430.
52 A.Z. Abdullah, N. Razali and K.T. Lee, J. Phys. Sci., 2010, 21
13-27.
,
53 C. Yu, B. Tian, J. Fan, G.D. Stucky and D.J. Zhao, J. Am. Chem.
Soc., 2002, 124, 4556-4557.
54 K. Flodström, V. Alfredsson and N. Källrot, J. Am. Chem. Soc.,
2003, 125, 4402-4403.
55 J. M. Kim and G. D. Stucky, Chem. Commun., 2000, 1159–
1160.
56 B. Naik and N. N. Ghosh, Recent Pat. Nanotech., 2009, 3,
213-224.
57 P. T. Tanev and T. J. Pinnavaia, Chem. Mater., 1996, 8, 2068 –
2079.
58 R. Bulánek, L. Čapek, M. Setnička and P. Čičmanec, J. Phys.
Chem. C, 2011, 115, 12430-12438.
59 M. S. Kumar, J. Pérez-Ramírez, M.N. Debbagh,B. Smarsly, U.
Bentrup and A. Brückner, Appl. Catal. B-Environ., 2006, 62
244–254.
,
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Artwork
Sucrose appeared effective template for mesoporous silica - efficient support of vanadia
catalyst, active in propene epoxidation to propylene oxide.