Anionic Amphiphilic Cyclodextrins Bearing Oleic Grafts for the Stabilization of Ruthenium Nanoparticles Efficient in Aqueous Catalytic Hydrogenation

Article abstract of DOI:10.1002/cctc.201901837

Oleic succinyl β-cyclodextrin was proved to be efficient for the stabilization of ruthenium nanoparticles (NPs) in aqueous medium. These NPs were characterized by FTIR spectroscopy and transition electron microscopy (TEM). The catalytic activity of these NPs was evaluated in the aqueous hydrogenation of petrosourced and biosourced unsaturated compounds such as benzene and furfural derivatives. The catalytic system can be easily recycled and reused up to nine runs without any loss of activity and selectivity, demonstrating its robustness.

Full text of DOI:10.1002/cctc.201901837

Accepted Article
Title: Anionic Amphiphilic Cyclodextrins bearing Oleic Grafts for the
Stabilization of Ruthenium Nanoparticles Efficient in Aqueous
Catalytic Hydrogenation
Authors: Aurélien Cocq, Bastien Leger, Sébastien Noel, Hervé Bricout,
Florence Pilard, Sébastien Tilloy, and Eric Monflier
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To be cited as: ChemCatChem 10.1002/cctc.201901837
Link to VoR: http://dx.doi.org/10.1002/cctc.201901837
A Journal of
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ChemCatChem
10.1002/cctc.201901837
COMMUNICATION
Anionic Amphiphilic Cyclodextrins bearing Oleic Grafts for the
Stabilization of Ruthenium Nanoparticles Efficient in Aqueous
Catalytic Hydrogenation
[
a]
[a]
[a]
[a]
[b]
Aurélien Cocq, Bastien Léger, Sébastien Noël, Hervé Bricout, Florence Djedaïni-Pilard,
[
Sébastien Tilloy and Eric Monflier*
a]
[a]
Abstract: Oleic succinyl β-cyclodextrin was proved to be efficient for
The recyclability of the catalytic system was also evaluated in the
the stabilization of ruthenium nanoparticles (NPs) in aqueous medium. case of furfuryl alcohol as substrate.
These NPs were characterized by FTIR spectroscopy and transition
electron microscopy (TEM). The catalytic activity of these NPs was
evaluated in the aqueous hydrogenation of petrosourced and
biosourced unsaturated compounds such as benzene and furfural
derivatives. The catalytic system can be easily recycled and reused
up to nine runs without any loss of activity and selectivity,
demonstrating its robustness.
The synthesis of OS-β-CD was carried out in two steps according
[
7]
to a previously described method. Briefly, the first step consists
in the alkenylation of maleic anhydride by oleic acid to produce an
oleic succinic anhydride (OSA). The second step involves the
grafting of the OSA on β-CD followed by a treatment with an
aqueous sodium hydroxide solution to give the carboxylate
functions. The degree of substitution is equal to 1.6, i.e. 1.6
hydroxyl group on 21 was functionalized by the oleic-succinyl
group. In Scheme 1, in order to simplify this representation, only
one kind of graft was presented, among the two possible, knowing
that each hydroxyl groups of the β-CD can react with one or the
other carbonyl group of the succinic anhydride. The water-
solubility and the critical aggregation concentration of OS-β-CD
Transition metal nanoparticles (NPs) are widely used in the field
[
1-3]
of catalysis.
This kind of catalytic system provides high active
surface area and can be dispersed in water by using capping
[
4]
agents. Among the described water-soluble capping agents,
cyclodextrins (CDs) are efficient biosourced molecules. CDs are
water-soluble chemical receptors consisting of six (α-CD), seven
-1
-1
were equal to 286 g.L and 170 mg.L , respectively (at 20°C).
[
5]
(
β-CD) or eight (γ-CD) 1,4-linked α-D-glucopyranose units. CDs
are able not only to include organic substrates into their
hydrophobic cavity but CDs can also interact with the metallic
nanoparticles surfaces. They have been employed under various
forms and environments such as free form (native or modified CD),
inclusion complex form with appropriate guests molecules (ionic
surfactants, phosphanes), or in combination with polymer
[
6]
matrices (physically or chemically incorporated). In this context,
easy accessible oleic succinyl-cyclodextrins were considered as
[
7]
eco-compatible capping agents. Indeed, CDs and oleic acid
derivatives are industrially produced from renewable resources.
In addition, this kind of structure contains different functional
moieties such as carboxylate function, oleic succinyl chain and
CD ring which could favor both electrostatic and steric
stabilizations of NPs in water. The presence of the hydrophobic
cavity of the CD could also promote the meeting between
hydrophobic substrate and NPs. In this communication, we report
that oleic succinyl-β-cyclodextrin (OS-β-CD) (Scheme 1) was
efficient to stabilize ruthenium nanoparticles. These NPs were
characterized by FTIR spectroscopy and transition electron
microscopy (TEM). The catalytic activity of these NPs was
evaluated in the aqueous hydrogenation of petrosourced (alkyl
olefins and benzene derivatives) and biosourced unsaturated
compounds (furfural derivatives, methyl oleate and citronellal).
Scheme 1. Schematic representation of OS-β-CD.
For the synthesis of ruthenium nanoparticules stabilized by OS-β-
CD (Ru_OS-β-CD NPs), the ruthenium salt Ru(NO)(NO ) (1
3 3
equiv.) and OS-β-CD (3 equiv.) were solubilized in water and
stirred for 30 min at room temperature before addition of sodium
borohydride (10 equiv.) as a reducing agent. Note that the 3
equivalents of OS-β-CD corresponds to almost 5 equivalents of
oleic graft and therefore to 10 equivalents of carboxylate functions
with respect to ruthenium. The color of the aqueous solution
changed from orange to dark brown once sodium borohydride
was added, illustrating the reduction of Ru(III) and the formation
of Ru NPs. The resulting colloidal suspension was kept under
stirring 18 h to permit the total transformation of NaBH
into sodium metaborate (NaBO ) by hydrolysis. An interaction of
NaBO with the metal nanoparticles is possible. The reduction of
4
excess
2
2
[
a]
b]
Dr. A. Cocq, Dr. B. Léger, Dr. S. Noël, Dr. H. Bricout, Prof. Dr. S.
Tilloy, Prof. Dr. E. Monflier, Univ. Artois, CNRS, Centrale Lille,
ENSCL, Univ. Lille, UMR 8181, Unité de Catalyse et Chimie du
Solide (UCCS), 62300 Lens, France. E-mail: eric.monflier@univ-
artois.fr; Homepage: http://www.uccs.univ-artois.fr/ericmonflier.htm
Prof. Dr. F. Djedaïni-Pilard, Laboratoire de Glycochimie des
Antimicrobiens et des Agroressources, LG2A, UMR 7378 CNRS,
Université de Picardie Jules Verne, 33 rue Saint-Leu, 80039 Amiens,
France.
the metal precursor has been studied by ATR-FTIR spectroscopy.
Fig. 1 plots the ATR-FTIR spectra of lyophilized samples
corresponding to ruthenium nitrosyl nitrate (Fig. 1a), ruthenium
nitrosyl nitrate after the addition of sodium borohydride (Fig. 1b),
OS-β-CD (Fig. 1c) and Ru_OS-β-CD NPs (Fig. 1d).
[
Supporting information for this article is given via a link at the end of
the document
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The spectrum of Ru(NO)(NO
3
)
3
showed absorption bands at 1270
-1
and 1840 cm corresponding respectively to the nitrate (νNO3) and
nitrosyl (νNO) stretching bands (Fig. 1a). After addition of NaBH
to a Ru(NO)(NO aqueous solution and stirring at room
temperature during 18h, the bands at 1270 and 1840 cm , related
4
3 3
)
-1
-
to NO
3
and NO moieties, disappear in the corresponding
spectrum (Fig. 1b). This modification can be explained by the
-
3
simultaneous reduction of Ru(III) and NO , followed by NO
[
8]
leaching. However, it should be noticed that in this case, no
stable NPs were formed since a sedimentation of black ruthenium
in water was observed. In Figure 1c, OS-β-CD IR spectrum
reveals bands coming from the vibrational modes of the glucosyl
-1
units carbon-oxygene single bonds [930-1150 cm ]. Stretching
-1
bands characteristic of carboxylate anionic groups [1550 cm ]
-1
and of carbonyl group of the ester moiety [1740 cm ] are also
clearly observed, together with a very weak signal due to the
-1
carbon-carbon double bond of the graft [around 1680 cm ]. At
higher wavenumbers, stretching bands of C-H bonds [2800-3020
-1
-1
cm ] and of the hydroxyl groups [3300 cm ] are also present. The
spectrum of Ru_OS-β-CD NPs also shows the disappearance of
nitrate and nitrosyl bands due to the reduction of the metallic
precursor into NPs (Compare Fig. 1d to Fig. 1a). Moreover, no
modification of the spectral features of the OS-β-CD was
observed, proving that its structure was not modified during the
synthesis of the NPs.
3 3 3 3 4
Figure 1. ATR-FTIR spectra of (a) Ru(NO)(NO ) ; (b) Ru(NO)(NO ) + NaBH ;
(c) OS-β-CD and (d) Ru_OS-β-CD NPs.
Figure 2. a) TEM image at a magnification of × 200 000 and b) size distribution of Ru_OS-β-CD NPs ; c) TEM image at a magnification of × 200 000 and d) size
distribution of Ru_β-CD NPs.
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Ru_OS-β-CD NPs were also characterized by transmission
electron microscopy (TEM). The TEM image revealed no
aggregation of metal nanoparticles. Ru_OS-β-CD NPs were
Without stabilizer or in the presence of oleic acid sodium salt, the
conversion of styrene was non-significant (Table 1; entries 1 and
2). This could be explained by a lack of stability before the
catalytic test. In the case of β-CD alone as protective agent, the
styrene was completely converted into ethylcyclohexane within 1h
(Table 1, entry 3). However, the Ru NPs were unstable and
precipitated during the reaction. The experiment performed in the
presence of a physical mixture of oleic acid sodium salt and β-CD
gave no conversion and the catalytic system became unstable
during the hydrogenation (Table 1, entry 4). The experiment
performed in the presence of OS-β-CD as stabilizer led to a total
conversion of styrene into ethylcyclohexane within 1h and with a
colloidal suspension perfectly stable at the end of the reaction
(Table 1, entry 5). Thanks to a kinetic monitoring, it should be
noticed that styrene was completely converted into
ethylcyclohexane within two successive reaction steps (see
Supporting Information). It means hydrogenation of styrene into
ethylbenzene followed by ethylbenzene into ethylcyclohexane.
This last experiment undoubtedly showed that the catalytic
system based on Ru_OS-β-CD NPs was efficient and stable. As
the oleic arm of OS-β-CD contains a carbon-carbon double bond,
the stability of OS-β-CD has been evaluated during the catalytic
experiment. It is important to underline that after 18h at 30°C
under 10 bar of hydrogen pressure, the carbon-carbon double
bond of the graft was not reduced as evidenced by NMR
experiments (see Supporting Information).
homogeneously dispersed with
a narrow size distribution
centered at 2.56 ± 0.60 nm with 80% of the NPs having a diameter
between 2 and 3 nm (Fig. 2a and 2b). The zeta potential of
Ru_OS-β-CD NPs was measured and equal to – 41 mV. This
value was in good agreement with zeta potential values measured
for NPs stabilized in the presence of carboxylate functions
[
9]
(
between – 40 mV and – 60 mV). This value is also in correlation
with good stability of the colloidal suspension in the aqueous
phase. As a control, Ru_β-CD NPs have been synthesized from
Ru(NO)(NO ) and native β-CD to study the influence of the
3 3
grafting on the cyclodextrin backbone on the dispersion and the
size of the Ru NPs. The TEM image of Ru_β-CD NPs (Fig. 2c and
2d) clearly shows that metal nanoparticles are organized into non-
ordered superstructures with a mean diameter of 3.97 ± 0.86 nm.
This kind of organization has also been reported in the literature
[
10]
for Ru NPs stabilized with methylated cyclodextrins. Moreover,
the size distribution is less narrow in the case of Ru_β-CD NPs
than in the case of Ru_OS-β-CD NPs and two different
populations can be distinguished, one centered on 3.5 nm and
another one centered on 6 nm. This TEM study proves the
beneficial effect of the grafting of the oleic unit on β-CD on the
size and the dispersion of Ru NPs in the aqueous phase.
The catalytic activity of the Ru_OS-β-CD NPs was first evaluated
in the aqueous hydrogenation of styrene as model substrate for
control experiments. The catalytic experiments were performed at
a temperature of 30°C, under a hydrogen pressure of 10 bar and
with a styrene/ruthenium molar ratio equal to 100. Some control
experiments were done under the same reaction conditions
always considering the same amount of ruthenium salt and
[a]
Table 2. Hydrogenation of various substrates in presence of Ru_OS-β-CD NPs
[
b]
Entry
Substrate
1-Octene
Products
Time (min)
220
1
2
3
4
5
6
7
8
9
Octane
Decane
NaBH
4
as described for the Ru_OS-β-CD NPs synthesis. More
1-Decene
640
precisely, Ru colloidal suspensions stabilized either by oleic acid
sodium salt, β-CD alone or by an oleic acid sodium salt/β-CD
physical mixture have been synthesized and tested.
1-Tetradecene
Anisole
Tetradecane
3800
80
Methoxycyclohexane
Ethylcyclohexane
[
a]
Table 1. Hydrogenation of styrene in the presence of Ru NPs
Styrene
60
NP Stability
Allylbenzene
Benzaldehyde
Benzyl alcohol
Methyl oleate
Citronellal
Propylcyclohexane
150
Time
Conv.
(%)[b]
Entry
Stabilizer
(
min)
360
360
60
Before
After
Hydroxymethylcyclohexane
Hydroxymethylcyclohexane
Methyl stearate
1140
780
catalysis
catalysis
1
2
3
(-)
<1
<1
No
No
No
No
nd
Oleic acid
sodium
10
11
12
3,7-dimethyloctan-1-ol
Tetrahydrofurfuryl alcohol
Tetrahydrofurfuryl alcohol
270
No
[
c]
salt
Furfural
840
[
d]
[g]
β-CD
100
Yes
Furfuryl alcohol
255
Oleic acid
sodium
[a] Reaction conditions: Ru (1×10-5 mol), OS-β-CD (3×10-5 mol), substrate (1×10
-
4
5
60
60
<1
No
No
salt + β-
3
mol), hydrogen pressure (10 bar), temperature (30 °C), stirring rate (750 rpm),
[b]
[
e]
CD
12 mL water; Time to get the final product with a yield of 100% determined by
GC analysis with external standard (decane, except dodecane for 1-decene).
[
f]
[g]
OS-β-CD
100
Yes
Yes
[
a]
-5
-3
Reaction conditions: Ru (1×10 mol), Styrene (1×10 mol), hydrogen
[
pressure (10 bar), temperature (30 °C), stirring rate (750 rpm), 12 mL water.
b]
Conversion of styrene determined by GC analysis with external standard
-5
[
c]
-5
[d]
[e]
(
decane),
Oleic acid sodium salt (5×10 mol).
-
β-CD (3×10 mol).
5
-5
Prepared by mixing β-CD (3×10 mol) and oleic acid sodium salt (5×10 mol).
OS-β-CD (3×10 mol). yield of 100% in ethylcyclohexane.
[
f]
-5
[g]
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To extend this catalytic study, the hydrogenation of other
substrates was investigated. All the catalytic results are
summarized in table 2 and the final products correspond to the
fully saturated substrates. In the case of alkenes with terminal
double bonds, the reaction time significantly increased with the
alkyl chain length (Table 2, entries 1-3). This tendency was
already described in the case of the aqueous hydrogenation of
[
11]
terminal olefins catalyzed by metallic NPs assisted by CDs. In
the presence of Ru_OS-β-CD NPs, anisole, styrene, allylbenzene,
benzaldehyde and benzyl alcohol were completely converted into
their fully saturated equivalent after 80, 60, 150, 1140 and 780
minutes, respectively (Table 2, entries 4-8). For styrene,
allylbenzene and benzaldehyde, the reduction took place in two
consecutive steps. The C=C (vinyl or allyl) or C=O bond were
firstly reduced followed by the reduction of the aromatic ring. As
an example, the figure 3 depicted the reaction profile of the
hydrogenation of benzaldehyde. This profile illustrates the
sequential nature of the reaction as benzaldehyde was firstly
hydrogenated into benzyl alcohol (99% of yield into 170 minutes),
which is subsequently hydrogenated into hydroxymethyl-
cyclohexane (100% of yield into 1140 minutes). In the case of
benzaldehyde and benzyl alcohol, the catalytic activities were
very low compared to other aromatic substrates (Table 2,
compare entries 4-6 to 7-8). The reaction profiles relative to
styrene and allylbenzene were presented in the Supporting
Information. The efficiency of these NPs was also evaluated on
substrates issued from biomass. The catalytic system based on
Ru_OS-β-CD NPs was inefficient for the reduction of methyl
oleate (Table 2, entry 9). This result is in accordance with the fact
that the carbon-carbon double bond of OS-β-CD oleic arm was
not reduced under these reaction conditions. The reduction of (±)
citronellal, a monoterpenoid present in the citronella oil, was also
considered. Citronellal can be reduced into citronellol, 3,7-
dimethyloctan-1-al and 3,7-dimethyloctan-1-ol (the fully saturated
product). Contrary to the previous examples, the different steps of
reduction took place simultaneously and maximum yields of
citronellol and 3,7-dimethyloctan-1-al were reached after 90
minutes (25% and 7%, respectively). Then, the both percentages
decreased and 3,7-dimethyloctan-1-ol was mainly produced (Fig.
Figure 4. Reaction profile for the hydrogenation of citronellal using Ru_OS-β-
-
5
-5
CD NPs. Reaction conditions: Ru (1×10 mol), OS-β-CD (3×10 mol), substrate
-
3
(1×10 mol), hydrogen pressure (10 bar), temperature (30 °C), stirring rate (750
rpm), 12 mL water.
The hydrogenation of furfural and furfuryl alcohol (produced from
plant materials rich in pentosans) was also evaluated. The
catalytic activity was better in the case of furfuryl alcohol than
furfural (Table 2, entries 11 and 12). This behaviour has already
been described and seems logical since in the case of furfural,
the carbonyl double bond has to be also reduced. From a kinetic
monitoring point of view, the hydrogenation of furfural into
tetrahydrofurfuryl alcohol takes place in two consecutive steps
(furfural into furfuryl alcohol and then furfuryl alcohol into
tetrahydrofurfuryl alcohol; see Supporting Information). This
reaction pathway has also been previously reported in the
literature in the case of Ru NPs stabilized by an anionic
[
6b]
cyclodextrin polymer.
4).
Figure 5. Reusability of the catalytic system Ru_OS-β-CD NPs in the
-
5
hydrogenation of furfuryl alcohol. Reaction conditions: Ru (1×10 mol), OS-β-
-
5
-3
CD (3×10 mol), furfuryl alcohol (0.5 ×10 mol), hydrogen pressure (40 bar),
temperature (30 °C), stirring rate (750 rpm), 12 mL water, 30 min. Yield in
tetrahydrofurfuryl alcohol determined by GC analysis with external standard
(decane).
Figure 3. Reaction profile for the hydrogenation of benzaldehyde using Ru_OS-
-
5
-5
β-CD NPs. Reaction conditions: Ru (1×10 mol), OS-β-CD (3×10 mol),
-
3
substrate (1×10 mol), hydrogen pressure (10 bar), temperature (30 °C), stirring
rate (750 rpm), 12 mL water.
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The recyclability of the catalytic system was also investigated by Experimental Section
reusing the aqueous catalytic phase for successive furfuryl
alcohol hydrogenation runs (Fig. 5). In this case, the furfuryl
alcohol /ruthenium molar ratio is equal to 50 and the hydrogen
pressure to 40 bar in order to reduce the reaction time. After the
first run (30 min), the product of the reaction was extracted with
chloroform. Although the OS-β-CD concentration was 25 times
higher than its critical aggregation concentration, no formation of
emulsion was observed. This point is essential to facilitate an
easy separation between the aqueous and the organic phases.
After decantation and chloroform removal, the aqueous
suspension was reloaded with furfuryl alcohol and dihydrogen in
the autoclave and reused under the same experimental
conditions. The Ru_OS-β-CD NPs can be recycled and reused
for at least 9 consecutive runs with similar yields (between 85-
Chemicals and reagents
Native β-cyclodextrin, abbreviated as β-CD, was kindly supplied
by Roquette Frères (Lestrem, France). All chemicals were
purchased from Aldrich Chemicals and Acros Organics and were
used without further purification. Ruthenium nitrosyl nitrate (1.5
wt% of Ru aqueous solution) was supplied by Strem Chemicals.
Characterization techniques
Transmission Electron Microscopy (TEM) was performed on a
Tecnai microscope (200 kV). The sample into powder was
deposited onto the carbon coated copper grid. All the TEM images
are gathered in Supporting Information. Metal particle size
distributions have been determined from the measurement of 199
particles for Ru_OS-β-CD NPs, 174 particles for Ru_OS-β-CD
NPs after the ninth catalytic run and 207 particles for Ru_β-CD
NPs. The nanoparticles were found in arbitrarily chosen area of
the images using the program ImageJ software. Zeta potential
measurements were carried out in water suspension using a
100 %) without any loss of the stability of the colloidal suspension.
The stability of Ru_OS-β-CD NPs was confirmed by TEM
experiments performed after the ninth run. The TEM image
revealed that NPs were still homogeneously dispersed with a
slightly larger size distribution centered at 3.43 ± 0.62 nm
Malvern Zetasizer Nano ZS at
(
a controlled temperature
25±0.1°C). The ξ-potential corresponds to the potential
(
compared to 2.56 ± 0.60 nm before catalysis experiment) and
with 75% of the NPs with size ranging from 2 to 3.5 nm (see
Supporting Information). Additionally, other experiments were
performed to check the absence of ruthenium in the extracted
organic phase. To this end, the organic phase extracted from the
difference between the dispersion medium and the electrical
double layer of the fluid attached to the dispersed particles. The
measurements are based on a Laser Doppler electrophoretic
mobility of the heterogeneous catalyst via the Helmholtz-
Smoluchowski equation ξ = (η/ε)μ
e
e
, where μ is defined as the
first and the ninth runs were reused at 30°C under 40 bar of H
2
ratio between the velocity of the heterogeneous catalyst and the
magnitude under the applied electric field, η is the viscosity of the
suspending liquid and ε stands for the dielectric conductivity of
water. The heterogeneous catalysts were analyzed without any
previous treatment. All the samples were analyzed in triplicate
using the DTS Software from Malvern Instruments to acquire the
phase plot and the zeta potential distribution. Fourier transform
infrared spectroscopy (FTIR) experiments were carried out in the
4000–400 cm region with a spectral resolution of 2 cm using a
Shimadzu IR Prestige-21 spectrometer equipped with a PIKE
MIRacle diamond crystal. The samples were always prepared as
follow : inorganic salts, organic compounds were dissolved in
HPLC water. To get a final volume for each sample of 12 mL, the
required volume of water is added. The solutions or dispersions
were kept under vigorous stirring during 18 hours and then
lyophilized. The dried samples were finally analyzed by FTIR
spectroscopy.
with fresh furfuryl alcohol. After 3 hours, the analysis of organic
phase by GC indicated no conversion of the fresh furfuryl alcohol
in the both cases. This absence of conversion showed that no
leaching of active ruthenium nanoparticles in the organic phase
occurred during the extraction step. These results are very
impressive since up to now only a CD/polymer combination could
allow such
a
good stability and good recyclability of
a
−
1
−1
[6c,11]
nanoheterogeneous catalytic system.
Indeed, in the case of
Ru NPs stabilized by a free form CD (methylated β-CD), a
destabilization of the catalytic system, was observed after the fifth
[10b]
recycling run.
In conclusion, we showed that oleic succinyl-β-cyclodextrin was
efficient for the synthesis of catalytically active ruthenium
nanoparticles. The TEM image revealed that Ru_OS-β-CD NPs
were homogeneously dispersed with a narrow size distribution
centered on 2.56 nm. These NPs were efficient for the
hydrogenation of olefins, aromatic and biosourced substrates. In
the case of furfuryl alcohol, the catalytic system can be easily
recycled and reused for several consecutive runs demonstrating
the robustness of this catalytic system. These preliminary results
are very promising since this is the first free form CD able to
efficiently stabilize Ru NPs during recycling experiments. So, this
easily synthesized oleic succinyl-β-cyclodextrin could find other
applications by varying the nature of the transition metal or
considering another catalytic reaction.
Synthesis of Ru_OS-β-CD NPs
In a typical experiment, the colloidal suspension was prepared as
follows at ambient temperature. 50.5 mg of the OS-β-CD (30
µmol, 3 molar equivalents with respect to ruthenium) were
dissolved in 5 mL of HPLC water. Besides this solution, 66.8 mg
(
10 μmol) of a 1.5 wt% ruthenium nitrosyl nitrate solution (10 µmol
of Ru) were diluted in 3 mL of water which was added to the
previous solution. The mixture was kept under constant stirring at
room temperature for 30 minutes before the addition of 4 mL of
0.025 M sodium borohydride solution (0.1 mmol, 10 molar
equivalents with respect to ruthenium). The color of the reaction
medium changed upon addition of NaBH from orange to dark
4
brown due to the reduction of Ru(III). The resulting colloidal
suspension was kept under stirring 18 h before their utilization for
the catalytic test to permit the total transformation of NaBH
excess into NaBO by hydrolysis. The final suspension is visually
stable for months and no sedimentation is observed.
4
2
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Catalytic test
Rousseau, H. Bricout, E. Oliva, V. Bonnet, F. Djedaini-Pilard, E. Monflier, S.
Tilloy, Eur. J. Org. Chem. 2019, 4863-4868.
All hydrogenation experiments have been performed using a
stainless steel autoclave Parker-Autoclave Engineers containing
a glass vessel which was charged with 12 mL of standard
ruthenium colloidal suspension and the desired substrate amount.
Hydrogen was fed to the system at constant pressure up to the
desired pressure. The mixture was heated up to 30 °C with a
thermostated oil bath and stirred at 750 rpm. Conversions and
selectivities were determined by GC analysis using the calibration
method with an external standard.
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The recycling experiments have been performed using furfuryl
alcohol as substrate. At the end of the reaction, all organic
compounds were extracted using chloroform. After decantation
and chloroform removal, the aqueous phase containing the
catalyst was reused for another run by reloading with furfuryl
alcohol and fed with hydrogen.
Acknowledgements
This work was performed, in partnership with the SAS PIVERT,
within the frame of the French Institute for the Energy Transition
(
(
Institut pour la Transition Energétique (ITE) P.I.V.E.R.T.)
http://www.institut-pivert.com) selected as an Investment for the
Future (Investissements d’Avenir). This work was supported, as
part of the Investments for the Future, by the French Government
under the reference ANR-001-01. The TEM facility in Lille
(
France) is supported by the Conseil Regional des Hauts de
France, and the European Regional Development Fund (ERDF).
We are grateful to Dr. Ahmed Addad for his contribution in setting
up the TEM measurements. Jérémy Ternel, Nicolas Kania, and
Dominique Prévost are acknowledged for NMR analysis and
technical assistance. PIVERT is acknowledged for the financial
support of AC thesis.
Keywords: • Cyclodextrins • Hydrogenation • Metal nanoparticles
•
Oleic acid • Supramolecular catalysis
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[
This article is protected by copyright. All rights reserved.

ChemCatChem
10.1002/cctc.201901837
COMMUNICATION
Entry for the Table of Contents
COMMUNICATION
Metallic nanoparticles and
cyclodextrin: Ruthenium
A. Cocq, B. Léger, S. Noël, H. Bricout,
F. Djedaïni-Pilard, S.Tilloy and E.
Monflier*
nanoparticles (NPs) are stabilized by
oleic succinyl-β-cyclodextrin in
water. These NPs were efficient in
the aqueous hydrogenation of
petrosourced and biosourced
substrates. The catalytic system can
be easily recycled and reused up to
nine runs.
Page No. – Page No.
Anionic Amphiphilic Cyclodextrins
bearing Oleic Grafts for the
Stabilization of Ruthenium
Nanoparticles Efficient in Aqueous
Catalytic Hydrogenation
This article is protected by copyright. All rights reserved.