Platinum nanoparticles supported on ionic liquid-modified-silica gel: Hydrogenation catalysts

Article abstract of DOI:10.1039/c4ra01066c

Platinum nanoparticles (ca. 2.3 nm) dispersed in ionic liquids and functionalized ionic liquids were supported within a silica network by the sol-gel method. The effect of the sol-gel catalyst (acid or base) on the encapsulated ionic liquid and on the platinum content was studied, and the silica morphology, the texture of the support material, and the hydrogenation activity were investigated. The Pt(0) content in the resulting xerogels (ca. 0.2 wt% Pt/SiO₂) was shown to be independent of the sol-gel process. The acidic conditions resulted in xerogels with larger pore diameters, which in turn might be responsible for the higher catalytic activity in hydrogenation of the alkenes and arenes obtained with the heterogeneous catalyst (Pt(0)/SiO ₂).

Full text of DOI:10.1039/c4ra01066c

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Platinum nanoparticles supported on ionic
liquid-modified-silica gel: hydrogenation catalysts
Cite this: RSC Adv., 2014, 4, 16583
a
a
b
Lucas Foppa, Jairton Dupont and Carla W. Scheeren*
Platinum nanoparticles (ca. 2.3 nm) dispersed in ionic liquids and functionalized ionic liquids were
supported within a silica network by the sol–gel method. The effect of the sol–gel catalyst (acid or base)
on the encapsulated ionic liquid and on the platinum content was studied, and the silica morphology,
the texture of the support material, and the hydrogenation activity were investigated. The Pt(0) content
Received 6th February 2014
Accepted 24th March 2014
2
in the resulting xerogels (ca. 0.2 wt% Pt/SiO ) was shown to be independent of the sol–gel process. The
acidic conditions resulted in xerogels with larger pore diameters, which in turn might be responsible for
the higher catalytic activity in hydrogenation of the alkenes and arenes obtained with the heterogeneous
DOI: 10.1039/c4ra01066c
www.rsc.org/advances
2
catalyst (Pt(0)/SiO ).
21,22
porous silica prepared in a sol–gel process.
nanoparticles (MNPs) with small diameter and narrow size
Supported Pt catalysts are used in various industrial processes distribution can be prepared by simple H reduction of metal
including hydrogenation, naphtha reforming, oxidation, auto- compounds or decomposition of organometallic species dis-
Moreover, metal
1
. Introduction
2
1
–7
23,24
motive exhaust catalysts, and fuel cells. Pt/SiO
model of Pt catalysts with SiO
SiO
relatively inert compared to other oxide supports, such as TiO2 ferred to other organic and inorganic supports to generate more
2
is a classical solved in ILs.
In several cases the MNPs are not stable and
8
25
tend to aggregate. Alternatively, these nanoparticles can be
2
as the “inert” oxide support.
resists reduction and has low surface acidity, making it used in conjunction with other stabilizers or be easily trans-
2
9
26–29
and Al O . These characteristics make Pt/SiO an ideal starting stable and active catalysts.
The nanoparticles/ionic liquid/
It is well known that stabilizer combination usually exhibits an excellent synergistic
several steps in the catalyst preparation process strongly inu- effect that enhances activity of the catalyst. So could be prepared
ence particle size in Pt/SiO
, including the support composition, more efficient and stable catalytic systems using the generation
2
3
2
10,11
point for study of the catalytic role of Pt.
2
metal salt, precursor deposition method, metal loading, pH, of metal nanoparticles associated with silica using ILs as
drying conditions, calcination temperature, and reduction templates for both catalytic partners i.e. the metal nanoparticles
1
2,13
30–34
temperature, among others.
The combination of an ionic liquid with a solid support
material is emerging as a new alternative for the immobilization ionic liquids and functionalized ionic liquids, can be applied
and the silica support.
We present herein our results which show that imidazolium
14,15
of transition metal catalyst precursors.
2
Imidazolium ionic for the generation of the heterogeneous catalyst (Pt(0)/SiO ) via
liquids (ILs) possess pre-organized structures mainly through sol–gel processes. The heterogeneous catalyst obtained (Pt(0)/
16
hydrogen bonds which induce structural directionality. These SiO
IL structures can adapt or be adaptable to many species, as they
provide hydrophobic or hydrophilic regions, and a high direc-
) was studied in hydrogenation reactions.
2
17,18
tional polarizability.
This structural organization of ILs can 2. Experimental
be used as “entropic drivers” for spontaneous, well-dened and
extended ordering of nanoscale structures. Indeed, the unique
combination of adaptability towards other molecules and pha-
ses associated to the strong hydrogen-bond driven structure
makes ionic liquids potential key tools in the preparation of a
2
.1. General
All experiments were performed in air, except for the synthesis of
the Pt(0) nanoparticles. The Pt(0) nanoparticles
halide-free BMI$PF
25,35
and the
(ref. 36a) and PMI$Si$(OMe) $X
ionic liquids were prepared according to
3
6a
6
3
,
BMI$BF
4
3
6b
(X¼ Cl, N(Tf)
2 6
, PF )
19,20
new generation of chemical nanostructures
such as template
literature procedure. Solvents, alkenes, and arenes were dried
with the appropriate drying agents and distilled under argon
prior to use. All other chemicals were purchased from
commercial sources and used without further purication. Gas
chromatography analysis was performed with a Hewlett–Pack-
ard-5890 gas chromatograph with an FID detector and a 30 m
a
Laboratory of Physical Chemistry, School of Chemistry and Food, Universidade
Federal do Rio Grande-FURG, Av. It a´ lia Km 08, 96201-900 Rio Grande, RS, Brazil
b
Institute of Chemistry, Laboratory of Molecular Catalysis UFRGS, Av. Bento
Gonçalves, 9500, 91501-970 B.O. Box 15003, Porto Alegre, RS, Brazil. E-mail:
carlascheeren@gmail.com
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capillary column with a dimethylpolysiloxane stationary phase. corresponding to each of the elements in the spectra and con-
The nanoparticles formation and hydrogenation reactions were verted to wt% Pt(0)/SiO2.
carried out in a modied Fischer–Porter bottle immersed in a
silicone oil bath and connected to a hydrogen tank. The
temperature was maintained at 75 C by a hot-stirring plate.
2
.6. Nitrogen adsorption–desorption isotherms
ꢀ
The adsorption–desorption isotherms of previous degassed
solids (150 C) were determined at liquid nitrogen boiling point
in a volumetric apparatus, using nitrogen as probe. The specic
ꢀ
2.2. Synthesis of Pt(0) nanoparticles supported in silica
Silica immobilized Pt(0) nanoparticles were prepared by the sol– surface areas of xerogels were determined from the t-plot
gel method under acidic and basic conditions. Procedure for analysis and pore size distribution was obtained using the BJH
acid catalysis: 10 mL of tetraethoxy orthosilicate (9.34 g, 45 method. Homemade equipment with a vacuum line system
mmol) was introduced in a Becker under vigorous stirring at 60 employing a turbo-molecular Edwards's vacuum pump was
ꢀ
C. The Pt(0) nanoparticles (10 mg, 0.05 mmol) were dissolved used. The pressure measurements were made using a capillary
in BMI$BF
4
(1 mL, 5.1 mmol) and ethanol (5 mL). This solution Hg barometer and a Pirani gauge.
was submitted to stirring and sonication for 2 min and then
added to the solution containing TEOS. Consecutively, an acid
solution (HF) was added as acid catalyst. The temperature was
kept at 60 C for 18 h. The resulting material was washed several
times with acetone and dried under vacuum.
Procedure for base catalysis: 10 mL of TEOS (9.34 g, 45
mmol) was added to ethanol (5 mL), containing the ionic liquid
4
BMI$BF (1 mL, 5.1 mmol) and previously isolated Pt(0) nano-
2
.7. Scanning electron microscopy (SEM) and electron
dispersive spectroscopy (EDS) elemental analysis
ꢀ
The materials were analyzed by SEM using a JEOL model JSM
5800 with 20 kV and 5000 magnication. The same instrument
was used for the EDS with a Noran detector (20 kV and acqui-
sition time of 100 s and 5000 magnication).
particles (10 mg, 0.05 mmol). Then ethanol (95 mL) and
ammonium hydroxide (20 mL) were added. The mixture was
2.8. Transmission electron microscopy (TEM) analysis
kept under stirring for 3 h at room temperature and le to stand The morphologies and the electron diffraction (ED) patterns of
for a further 18 h. The resulting xerogel was ltered and washed the obtained particles were determined on a JEOL JEM-2010
with acetone and dried under vacuum for 1 h.
equipped with an EDS system and a JEOL JEM-120 EXII electron
microscope, operating at accelerating voltages of 200 and 120
kV, respectively. The TEM samples were prepared by deposition
2.3. X-ray diffraction (XRD)
of the Pt(0) nanoparticles or Pt(0)/SiO isopropanol dispersions
2
The phase structures were characterized by of XRD Pt(0) nano-
particles. For XRD analysis, the nanoparticles were isolated as a
on a carbon-coated copper grid at room temperature. The
histograms of the nanoparticle size distributions were obtained
from the measurement of around 300 diameters and repro-
duced in different regions of the Cu grid assuming spherical
shapes.

ne powder and placed on the specimen holder. The XRD
experiments were performed in a SIEMENS D500 diffractometer
equipped with a curved graphite crystal using radiation Cu Ka (l
˚
¼
1.5406 A). The diffraction data were collected at room
temperature in Bragg–Brentano geometry q–2q. The equipment
2.9. Catalytic hydrogenations
ꢀ
was operated at 40 kV and 20 mA with a scan range between 20
ꢀ
and 90 . The diffractograms were obtained with a constant step The catalysts (150 mg) were placed in a Fischer–Porter bottle
D2q ¼ 0.05. The indexation of Bragg reections was obtained by and the alkene or arene (12.5 mmol) was added. The reactor was
37
ꢀ

tting a pseudo-Voigt prole using the code FULPROFF code.
placed in an oil bath at 75 C and hydrogen was admitted to the
Nanoparticles Pt(0)/SiO
2
were analyzed on a glass substrate.
system at constant pressure (4 atm) under stirring until the
consumption of hydrogen stopped. The organic products were
recovered by decantation and analyzed by GC. The re-use of the
catalysts were performed by simple extraction of the organic
phase (upper phase) followed by the addition of the arene or
alkene. Aer eleven recyclings the solid was isolated, re-
dispersed in isopropanol and placed in a cooper carbon grid.
2.4. Elemental analysis (CHN)
The organic phases present in the xerogels were analyzed using
CHN elemental Perkin Elmer elemental CHNS/O analyzer,
model 400. Triplicate analysis of the samples, previously heated
ꢀ
at 100 C under vacuum for 1 h, was carried out.
3
. Results and discussion
2.5. Rutherford backscattering spectrometry (RBS)
Platinum loadings in catalysts were determined by RBS using The sol–gel process is considered as a so chemical approach
+
He beams of 2.0 MeV incidents on homogeneous tablets of the for the synthesis of metastable oxide materials, this process
38
compressed (12 MPa) catalyst powder. The method is based on allows us to obtain solid products by creating an oxide network
the determination of the number and energy of the detected via progressive polycondensation reactions of molecular
33,39
particles which are elastically scattered in the Coulombic eld precursors in a liquid medium.
Essentially two steps are
of the atomic nuclei in the target. In this study, the Pt/Si atomic involved: hydrolysis and condensation. Both reactions are
ratio was determined by the heights of the signals affected by the nature of the catalyst. Therefore, in the present
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weakly branched structure generated in the presence of acid
catalyst (either HF) guarantees the retention of the ionic liquid.
Rutherford backscattering spectrometry (RBS) was used in
the determination of the metal contents. The Table 1 shows that
the immobilized Pt content is roughly the same for silica
prepared by both routes, corresponding to ca. 65–75% of the
initial Pt content employed in the synthesis. The metal distri-
bution in the support was determined by SEM-EDX analysis.
The mapping showed a homogeneous Pt distribution in the
silica grains, independently of the preparative route. The Fig. 2
shows SEM micrograph of Pt(0)/SiO2 synthesized using acid
conditions by sol–gel method. The micrograph shows lighter
regions, indicating the presence of platinum metal nano-
particles on the silica matrix (gray regions). The elemental
Fig. 1 XRD analysis of: (A) Pt(0) nanoparticles and (B) XRD analysis of
Pt(0)/SiO .
2
study, two main routes were evaluated: (i) using an acid catalyst composition of the region focused on the micrograph conrms
HF), or (ii) using a base catalyst (NH OH). In both routes, the this structure. Samples Pt(0)/SiO were analyzed by the scanning
(
4
2
hydrolysis and condensation of tetraethoxy orthosilicate (TEOS) point and area exposed to the electron beam. All selected areas
were performed in the presence of Pt(0) nanoparticles, which showed the presence Pt(0) in the silica matrix. In the micro-
2 3
were prepared by hydrogen reduction (4 atm) of Pt (dba) dis- graph, the metal is identied by the bright regions in contrast to
ꢀ
19
solved in the ionic liquids at 75 C. These nanoparticles
obtained presented 2.3 nm of diameter. Fig. 1 shows the XRD
pattern of Pt(0) nanoparticles and Pt(0) nanoparticles encap-
sulated in silica matrix showing the diffraction planes of silica
and Platinum (Pt(0)/SiO ). This material was obtained by sol–gel
2
synthesis under acidic conditions using the liquid having
BMI$PF
Table 1 presents the elemental analysis of the resulting plat-
inum nanoparticles supported in silica Pt(0)/SiO . Is possible
6
amount of Pt(0) <0.2% compared to silica.
2
observe that carbon and nitrogen content was taken as a sign for
the presence of ionic liquids once encapsulated within the silica
Fig. 2 Micrograph obtained by SEM of the resulting xerogel: (A) Pt(0)/
/HF, and EDX corresponding (B).
network (compare entries 2, 4, 6, 8 with entries 3, 5, 7, 9). Based SiO
on the results shown in Table 1, higher ionic liquid contents were
incorporated with the acid catalysts. It is worth noting that in the
case of acidic conditions, hydrolysis is faster than condensation.
The rate of condensation slows down with increasing
number of siloxane linkages around a central silicon atom. This
leads to formation weakly branched polymeric networks. The
condensation, in case of basic conditions, is more accelerated
relative to hydrolysis. The rate of condensation increases with
increasing number of siloxane bridges, resulting in the forma-
2
34,40
tion of highly branched networks.
In the present case, based
Fig. 3 Micrographs obtained by M of the resulting xerogels: (A) Pt(0)/
on the carbon and nitrogen contents, it seems that the resulting SiO
2 2 4
/HF (acid) and (B) Pt(0)/SiO /NH OH (basic).
a
Table 1 Elemental analysis of Pt(0)/SiO
2
ꢁ1
ꢁ1
ꢁ1
a
Entry
Sample
C/mmol g
H/mmol g
N/mmol g
Pt(0) %
1
2
3
4
5
6
7
8
9
Pt/SiO
Pt/SiO
Pt/SiO
Pt/SiO
Pt/SiO
Pt/SiO
Pt/SiO
Pt/SiO
Pt/SiO
2
2
2
2
2
2
2
2
2
/NH
/HF
/NH
4
OH
OH/BMI$PF
3.9
5.7
4.4
12.4
9.9
18.7
10.2
16.4
12.4
0.6
1.6
1.4
2.9
2.1
3.3
2.5
3.5
1.7
1.7
1.5
1.0
5.1
4.1
3.8
2.8
6.6
3.2
0.19
0.2
0.18
0.17
0.2
0.18
0.18
0.2
4
6
/HF/BMI$Cl
/NH OH/BMI$Cl
/HF/MIPSi(OMe)
/NH OH/MIPSi(OMe)
/HF/MIPSi(OMe) $N(Tf
/NH OH/MIPSi(OMe) $(NTf
4
3
$Cl
4
3
$Cl
2
)
3
4
3
2
)
0.22
a
Determined by RBS.
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accordance to that usually observed for pure silica synthesized
by these routes. In the case of acid-catalyzed conditions, a less
organized, plate-like structure was observed, while in the case of
basic conditions, spherical particles were obtained (indeed
shown in more detail in Fig. 4). It is worth noting that smaller
particles were produced in the latter case.
Transmission electron microscopy (TEM) was also employed
for the characterization of the supported catalyst. Fig. 5 (top)
shows the micrograph of the isolated Pt(0) particles, and their
mean size, which was shown to be ca. 2.3 nm. In the case of
Pt(0)/SiO Fig. 5 (bottom) prepared by acid catalysis (HF), both
2
the morphology and size (ca. 2.3 nm) were maintained within
the silica framework. It is very likely that the presence of ionic
liquid affords stability, avoiding sintering of the metallic
particles. The same behavior was observed for the material
prepared by the base catalysis.
2
Fig. 4 Micrograph obtained by SEM of the resulting Pt(0)/SiO /
NH OH (basic).
4
The textural properties were further characterized by nitrogen
adsorption. The specic area was calculated by the BET method,
while pore diameter, by the BJH one (Table 2). According to Table
2
, the silicas prepared in the absence of Pt(0) presented higher
2
ꢁ1
specic area (ca. 100 m g ). The introduction of nanoparticles
during the synthesis, independently of the synthetic route, led to
a reduction in the specic area. The pore diameter was demon-
4
strated to be smaller for the materials when NH OH was used as
catalyst. The pore volume was shown to be independent of the
presence of Pt(0) in acidic or basic conditions. The supported
catalysts were evaluated in hydrogenation reactions.
Table 3 presents data regarding 1-decene, cyclohexene and
benzene hydrogenation reactions. For comparative purposes we
also included the data concerning the catalytic activity of iso-
19
lated Pt(0) nanoparticles. In the benzene hydrogenations
experiments, the product obtained was always the cyclohexane.
The catalytic activity of the heterogeneous catalysts studied
in this work were expressed using the turnover frequency (TOF),
Fig. 5 TEM micrographs and histograms showing the particle size
distribution of: (A) Pt(0) nanoparticles and (B) Pt(0)/SiO /HF.
(
1
the TOF values were estimated for low substrate conversions,
0%), and that they should also be corrected by the number of
exposed surface atoms by using the metal atom's magic number
2
41
approach.
Table 3 shows the results obtained in the hydrogenation
the array of silicon that has the dark background. Fig. 3 illus-
trates the micrography of Pt(0)/SiO prepared by both routes,
acid and basic. According to Fig. 3, particle morphologies are in
2
reactions using the system Pt(0)/SiO
2
. For comparison effects
a
2
Table 2 Surface area, pore volume and average pore diameter of Pt(0)/SiO
2
ꢁ1
3
ꢁ1
E.
Sample
S
BET/m g
V
p
/cm g
p
d /nm
1
2
3
4
5
6
7
8
9
Pt(0)/SiO
Pt(0)/SiO
Pt(0)/SiO
Pt(0)/SiO
Pt(0)/SiO
Pt(0)/SiO
Pt(0)/SiO
Pt(0)/SiO
Pt(0)/SiO
Pt(0)/SiO
Pt(0)/SiO
Pt(0)/SiO
2
2
2
2
2
2
2
2
2
2
2
2
/HF
/HF/BMI$BF
/HF/BMI$PF
/NH
/NH
/NH
/HF/MIPSi(OMe)
/NH OH/MIPSi(OMe)
/HF/MIPSi(OMe) $N(Tf)
/NH OH/MIPSi(OMe)
/HF/MIPSi(OMe) $PF
/NH OH/MIPSi(OMe)
162
118
32
106
102
0.1
0.2
1.8
8.8
1.9
4.8
4.3
4
6
0.02
0.2
0.07
0.009
0.03
0.2
4
4
4
OH/BMI$BF
4
OH
OH/BMI$PF
6
6.2
18
3.9
3
$Cl
66
193
98
248
202
239
4
3
$Cl
2.8
5.2
2.8
2.7
2.8
3
2
0.3
1
1
1
0
1
2
4
3
$N(Tf)
2
0.28
0.23
0.27
3
6
4
3
$PF
6
a
S
BET ¼ specic area determined by BET method. V
p
¼ pore volume, d
p
¼ pore diameter.
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a
2
b
Table 3 Hydrogenation of alkenes/arene by Pt(0)/SiO
and Pt(0) nanoparticles
ꢁ1
c
ꢁ1
Ent.
Catalyst
Ionic liquid
Substrate
Time (h)
TOF (h
)
TOF (h
)
a
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
Pt(0)/SiO
2
2
2
2
2
2
2
2
2
2
2
2
2
/HF
/HF
/HF
/NH
/NH
/NH
/HF
/NH
/HF
/NH
/HF
/NH
/HF
BMI$BF
BMI$BF
BMI$BF
BMI$BF
BMI$BF
BMI$BF
MIPSi(OMe)
MIPSi(OMe)
MIPSi(OMe)
MIPSi(OMe)
MIPSi(OMe)
MIPSi(OMe)
MIPSi(OMe)
—
4
4
4
4
4
4
1-Decene
Cyclohexene
Benzene
1-Decene
Cyclohexene
Benzene
1-Decene
Cyclohexene
1-Decene
1-Decene
1-Decene
1-Decene
1-Decene
1-Decene
Cyclohexene
Benzene
0.4
0.8
1.8
2.5
6
156
78
35
25
11
—
416
52
104
78
125
57
400
200
90
64
28
a
Pt(0)/SiO
a
Pt(0)/SiO
a
Pt(0)/SiO
4
4
4
OH
OH
OH
a
Pt(0)/SiO
a
Pt(0)/SiO
—
—
a
Pt(0)/SiO
3
3
3
3
3
3
3
$N(Tf)
$N(Tf)
2
2
0.15
1.2
0.6
0.8
0.5
1.1
0.7
0.9
1.6
10
1067
133
267
200
320
146
230
72
a
Pt(0)/SiO
4
OH
4
OH
4
OH
a
Pt(0)/SiO
$PF
$PF
$Cl
$Cl
$PF
6
a
0
1
2
3
4
5
6
Pt(0)/SiO
6
a
Pt(0)/SiO
a
Pt(0)/SiO
a
Pt(0)/SiO
6
90
28
16
2.5
b
Pt(0)
b
Pt(0)
—
—
41
6.4
b
Pt(0)
a
ꢀ
Conditions: H
2
pressure (4 atm), temperature 75 C, ratio [alkene/arene]/[Pt(0)/SiO
2
] ¼ 625/1, added Pt/SiO
2
(150 mg, 0.025 mmol) Pt(0) followed by
b
1
2.5mmolofalkenesorarenesused. Pt(0) nanoparticles 10mg, ratio[arene]/[Pt(0)]¼ 250/1, addedPt(0)(10mg), followedby12.5mmolof thealkenes
c
or arenes used. TOF values were calculated for 10% conversion. TOF values corrected using the number of exposed surface metal atoms (39%).
were added results using only the Pt(0) nanoparticles in
hydrogenation reactions (entry 21–23, Table 3). Is possible
observe that all the supported systems were more active than
those constituted of only Pt(0) nanoparticles. Among the silica-
based systems, those prepared under acidic conditions are the
most active, exhibiting higher TOF in comparison to those of
isolated Pt(0) nanoparticles. The denser and bulkier structure
generated under basic conditions might have afforded less
2
active systems as shown by some clues. First, the ionic liquid Fig. 7 TEM micrographs of: (A) Pt(0)/HF/SiO isolated after eleven
recycles and (B) histogram showing the particle size distribution.
content, which seems to be important in order to guarantee
stability for the nanoparticles, was lower for these systems.
Besides, according to porosimetric measurements, the pore
diameter was much smaller for the Pt(0)/NH OH/SiO system.
4 2
Pt(0) encapsulated particles, in spite of a slightly higher content
under basic conditions. The hydrogenation of simple arenes
and alkenes by Pt(0)/HF/SiO depends on steric hindrance at the
2
C]C double bond and follows the same trend as observed with
classical platinum complexes in homogeneous conditions, that
is, the reactivity follows the order: terminal–internal. Finally,
the catalytic material can be recovered by simple decantation
and re-used at least eleven times without any signicant loss in
catalytic activity (see Fig. 6). The recovered material shows no
sign of agglomeration as observed from the TEM analysis of
in comparison to that afforded with an acid catalyst (see Table
3), might be not accessible in the supported systems prepared
2
Pt(0)/HF/SiO (representative image of the all sample observed
by TEM) catalyst isolated aer eleven recycles (Fig. 7).
In the Fig. 6 is possible observe that loss of catalytic activity
(observe recycles 6–8, Fig. 6) and aer in nine recycle activity
increases again. This fact can be related to the leaching of the
surface of Pt(0) nanoparticles, cleaning the metal surface,
making it active again.
4. Conclusions
The Pt(0) nanoparticles dispersed in ionic liquids and func-
tionalized ionic liquids can be easily supported within a silica
network using the sol–gel method (acid or base catalysis). The
Pt(0) content in the resulting xerogels was shown to be
Fig. 6 Conversion curves of 1-decene hydrogenation by Pt(0)/SiO
2
ꢀ
nanoparticles at 4 atm H
2
and 75 C.
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independent of the preparative route, but acidic conditions 16 A. Riisager, R. Fehrmann, M. Haumann and
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