The superior performance of a Pt catalyst supported on nanoporous SiC-C composites for liquid-phase selective hydrogenation of cinnamaldehyde

Article abstract of DOI:10.1039/c6ra15164g

The monometallic Pt catalyst supported on nanoporous composites containing β-SiC and amorphous carbon was proved to be active and selective for liquid-phase selective hydrogenation of cinnamaldehyde (CAL) even at room temperature. A TOF of higher than 2400 h^-1 and 80% selectivity to cinnamyl alcohol (COL) were furnished by the Pt/SiC-C catalyst at 25 °C. Moreover, the Pt/SiC-C nanocatalyst showed superior performance compared to other Pt catalysts supported on carbon, silica or alumina materials under the same conditions for the tested reaction. Of particular note is that the Pt/SiC-C catalyst can be easily recovered and reused for at least 10 runs without any loss in activity or selectivity. We deduce that there is a strong interaction between Pt nanoparticles and SiC-C composites; so that there are still quite a few Pt species with positive charges on the catalyst surface even after being reduced in an aqueous solution of sodium formate at reflux temperature and pre-treated under a hydrogen flow at 400 °C, which would be helpful for preferential adsorption and activation of CAL via electrostatic interaction with the oxygen atoms of the carbonyl group of CAL, and thus COL was the primary product obtained with the Pt/SiC-C catalyst.

Full text of DOI:10.1039/c6ra15164g

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The superior performance of a Pt catalyst
supported on nanoporous SiC–C composites for
liquid-phase selective hydrogenation of
cinnamaldehyde†
Cite this: RSC Adv., 2016, 6, 81211
*
Ruihua Yao, Junrui Li, Peng Wu and Xiaohong Li
The monometallic Pt catalyst supported on nanoporous composites containing b-SiC and amorphous
carbon was proved to be active and selective for liquid-phase selective hydrogenation of
cinnamaldehyde (CAL) even at room temperature. A TOF of higher than 2400 hÀ1 and 80% selectivity to
cinnamyl alcohol (COL) were furnished by the Pt/SiC–C catalyst at 25 ꢀC. Moreover, the Pt/SiC–C
nanocatalyst showed superior performance compared to other Pt catalysts supported on carbon, silica
or alumina materials under the same conditions for the tested reaction. Of particular note is that the Pt/
SiC–C catalyst can be easily recovered and reused for at least 10 runs without any loss in activity or
selectivity. We deduce that there is
a strong interaction between Pt nanoparticles and SiC–C
composites; so that there are still quite a few Pt species with positive charges on the catalyst surface
even after being reduced in an aqueous solution of sodium formate at reflux temperature and pre-
treated under a hydrogen flow at 400 ꢀC, which would be helpful for preferential adsorption and
activation of CAL via electrostatic interaction with the oxygen atoms of the carbonyl group of CAL, and
thus COL was the primary product obtained with the Pt/SiC–C catalyst.
Received 11th June 2016
Accepted 19th August 2016
DOI: 10.1039/c6ra15164g
www.rsc.org/advances
thermal conductivity. However, the relevant researches about the
utilization of SiC nanostructures as support for traditional
liquid-phase catalysis are still very limited.19,20 Sometimes,
Introduction
Silicon carbide (SiC) has attracted much more attention in
optical and electrical elds recently as one of the most impor-
tant semiconductors, due to its wide bandgap, high strength,
high thermal conductivity, good thermal shock resistance, low
thermal expansion and good chemical inertness.1,2 Indeed, the
SiC nanomaterial has been a rising star, as demonstrated by an
increasing number of published research about it.3 SiC nano-
structures have been successfully used as a photo-catalyst4–6 and
electro-catalyst7–13 owing to their specic properties. In addi-
tion, they have been reported as an efficient support or direct
metal-free catalyst for various reactions during the last
decades.14–18 Recently, the thermally conductive SiC, pure or
doped with different promoters, has been conrmed to be
active, selective and reusable for the Fisher–Tropsch reac-
tion.14,15 In addition, silicon carbide was also applied as a metal-
free catalyst for dehydrogenation of ethylbenzene to styrene.16,17
In general, silicon carbide was usually involved in some
strongly exothermic gas–solid phase reactions due to its high
silicon carbide with low specic surface area would restrict the
dispersion of active sites and hinders its application in hetero-
geneous catalysis to some extent. Therefore, nanoporous SiC–C
composites not only can reserve the special property of SiC itself,
but also have large specic surface area to disperse active sites.
Herein, we developed a monometallic Pt catalyst supported
on nanoporous SiC–C composites with large specic surface area
for liquid-phase selective hydrogenation of CAL (Scheme 1). As
well known, the selective hydrogenation of a,b-unsaturated
aldehydes is challengeable in that the formation of desirable a,b-
unsaturated alcohol is not thermodynamically preferred due to
higher C]O double bond energy than that of C]C double
bond.21 With regards of the selective hydrogenation of CAL,
special supports such as graphene or carbon nanotubes for
loading monometallic Pt catalyst21–27 or bimetallic catalysts (such
as Pt–Fe)21,28,29 are usually required to achieve high selectivity to
the desired COL. With attractive physico-chemical properties of
SiC and large specic surface area of nanoporous SiC–C
composites, we expected that there would be special interaction
between Pt nanoparticles and nanoporous SiC–C composites
and so that the surface electronic state of Pt nanoparticles might
be modulated and thus be benecial for preferential adsorption
and activation of CAL to form the desired product COL.
Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of
Chemistry and Molecular Engineering, East China Normal University, 3663 North
Zhongshan Rd., Shanghai 200062, China. E-mail: xhli@chem.ecnu.edu.cn; Fax: +86-
21-62238590; Tel: +86-21-62238590
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c6ra15164g
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Scheme 1 Selective hydrogenation of CAL.
Elemental IRIS Intrepid II XSP inductively coupled plasma-
atomic emission spectroscopy (ICP-AES). The thermogravi-
metric (TG) analysis of the samples was conducted from r.t. to
800 ꢀC under air atmosphere with Mettler Toledo TGA/
SDTA851e apparatus. The IR spectrum was measured with
a Nicolet NEXUS 670 spectrometer. The Raman spectrum of
sample was taken on a Renishaw inVia Raman Spectrometer
excited using a 514 nm laser.
To explain the superiority of SiC–C supported Pt catalyst
towards the selective hydrogenation of CAL, the Pt/SiC–C catalyst
was further characterized using XPS with a Thermo Fisher
Scientic ESCALAB 250Xi spectrometer with Al Ka radiation
(1486.6 eV) as incident beam with a monochromator. The
sample was in situ pre-treated in owing hydrogen at 400 ꢀC for 1
h in a reactor attachment of the XPS spectrometer. The binding
energy (BE) was calibrated using C–C binding energy at 284.4 eV
in order to compare the binding energies with the data from the
literatures. The spectra shown in the gures have been corrected
by subtraction of a Shirley background. Spectral tting and peak
integration was done using the XPSPEAK soware.
Experimental
Catalyst preparation
The monometallic 5 wt% Pt/SiC–C catalyst was prepared using
an ultrasound-promoted impregnation method. In a typical
process, 0.4218 g SiC–C powder was rstly treated under
vacuum for 10 minutes at 90 ꢀC. Then, SiC–C was rapidly added
to 2 mL aqueous solution of chloroplatinic acid containing 22.2
mg Pt followed by a vigorous stirring for about 1 min to ensure
that the solid powder was mixed well with liquid quickly. The
SiC–C was impregnated with the Pt precursor in an ultrasonic
instrument for 4 h. Then, the catalyst precursor was drying at 80
ꢀC to remove the excess solvent. Finally, the catalyst precursor
was reduced in an aqueous solution of sodium formate at
a reuxed temperature (95 ꢀC) and washed with plenty of water
to remove chlorine ions.
For comparison, monometallic 5 wt% Pt catalysts supported
on other materials, such as SBA-15 silica, CMK-3 carbon repli-
cated from SBA-15, and S16-C carbon replicated from SBA-16
silica, were also prepared using the same method as the Pt/
SiC–C catalyst. SBA-15 silica, CMK-3 carbon and SBA-16 silica
were prepared according to ref. 30–32. S16-C carbon was repli-
cated using SBA-16 silica as a hard template and sucrose as
carbon source according to the method with which CMK-3
carbon was prepared. In addition, 5 wt% Pt/C and Pt/Al2O3
catalysts were also purchased from Alfa Aesar as reference
catalysts.
Catalytic reaction
In a typical reaction, 0.03 g 5 wt% Pt/support was pre-treated
under a owing hydrogen (40 mL minÀ1) at 400 ꢀC for 2 h
before use. The catalyst was then transferred to a 100 mL
autoclave and mixed with solvent (18 mL isopropanol and 2 mL
water) and substrate (960 mL CAL). The reaction began when
hydrogen (2.0 MPa) was introduced with stirring (1200 rpm) at
a required temperature. The reaction was stopped aer 1 h and
the products were analyzed by GC-FID (GC-2014, Shimadzu)
equipped with a capillary column (DM-WAX, 30 m  0.25 mm
 0.25 mm). The response factor of each component was
calculated using standard samples and was used to calculate
the conversion and selectivity. Aer each run, the catalyst was
recovered by centrifugation and washed with fresh solvent for
several times. Then, fresh reactant and solvent were charged to
the autoclave together with the recovered catalyst to conduct the
next run reaction.
Catalyst characterization
The catalyst was characterized in detail with many physico-
chemical techniques. The XRD patterns of samples were
collected on a Bruker D8 Advance instrument using Cu-Ka
radiation. The nitrogen adsorption–desorption isotherms were
ꢀ
measured at À196 C (77 K) on a Quantachrome Autosorb-3B
system, aer the samples were evacuated for 10 h at 200 ꢀC.
The BET specic surface area was calculated using adsorption
data in the relative pressure range from 0.05 to 0.30. The pore
size distributions were calculated from the analysis of the
adsorption branch of the isotherm using the BJH algorithm.
The SEM images were taken on a Hitachi S4800 electro-
microscope with an acceleration voltage of 20 kV. The TEM
images were taken on an FEI Tecnai G2-TF30 microscope at an
Results and discussion
Catalyst characterization
acceleration voltage of 300 kV. The Pt loading on samples and The nanoporous SiC–C composites were purchased from Suz-
the leached Pt amount in ltrate was detected with a Thermo hou Yuhao Nanomaterials Inc. (Suzhou, China). The
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composites were detected by TG analysis under an air atmo- C catalyst, which was conrmed by the XRD pattern of Pt/SiC–C
sphere to determine the composition and the weight ratio of C/ catalyst. Additionally, the Pt/SiC–C catalyst also gave typical but
SiC was about 1.2 (Fig. S1, ESI†). The 5 wt% Pt/SiC–C catalyst weak diffraction peaks assigned to Pt(111), Pt(200) and Pt(220)
was prepared by an ultrasound promoted impregnation method planes, indicating that the Pt particles were well dispersed on
followed by reduction in an aqueous solution of sodium the nanoporous SiC–C composites surface without formation of
formate. According to the ICP-AES result, the nal Pt loading in large aggregation.
the Pt/SiC–C catalyst was the same as the nominal value. This
The porous structure and specic surface area of the SiC–C
demonstrates that the interaction between Pt nanoparticles and composites and the Pt/SiC–C catalyst was also determined using
SiC–C composites was extremely high so that the Pt nano- nitrogen sorption (Fig. 1(b)). Both the SiC–C composites and the
particles could not be washed off from the support surface Pt/SiC–C catalyst showed type IV isotherms, suggesting there
during the liquid-phase reduction at a reuxed temperature (95 are mesoporous pores although the hysteresis loops were not so
ꢀC). The liquid-phase selective hydrogenation of CAL was large. The pore size of Pt/SiC–C and SiC–C centered at 3.6 nm
carried out in a stainless-steel autoclave equipped with a heater (inset of Fig. 1(b)). For clarity, Table 1 lists the detailed physi-
and a magnetic stirrer.
cochemical parameters of the SiC–C composites and the Pt/SiC–
The structure and crystalline phase of nanoporous SiC–C C catalyst. The BET specic surface area of Pt/SiC–C was
composites and Pt/SiC–C catalyst was rstly characterized using comparable with that of SiC–C composites, having a large
XRD. As displayed in Fig. 1(a), nanoporous SiC–C composites specic surface area of more than 330 m2 gÀ1. The pore volume
gave typical diffraction patterns associated to (111), (220) and of the Pt/SiC–C catalyst was also comparable to that of SiC–C
(311) planes of b-SiC besides weak stacking faults at 2 theta composites, demonstrating the deposition of Pt nanoparticles
angle of 35ꢀ.11 In addition, the diffraction peak assigned to did not block the pore entrance of SiC–C composites. We also
amorphous carbon was also observed at around 2 theta of 25ꢀ. characterized the Pt/SiC–C catalyst using Raman and infrared
The b-SiC crystalline phase was well retained in the nal Pt/SiC– spectroscopy. As displayed in Fig. S2,† the Pt/SiC–C catalyst
showed a typical Si–C vibration band at around 835 cmÀ1, while
for the Raman spectra of SiC–C composites and Pt/SiC–C cata-
lyst, only G and D bands assigned to sp2 hybridized carbon were
observed and the typical Si–C vibration band was not detected
(Fig. S3†). It indicates that SiC was covered by carbon with thick
layers, so that the signal of SiC could not be detected.
The morphology of Pt/SiC–C catalyst was characterized using
SEM (Fig. 2(a) and (b)). The SiC–C composites exhibited irreg-
ular shapes with broccoli-like aggregation. The Pt particle size
distribution of the Pt/SiC–C catalyst was also characterized
using TEM. As exhibited in Fig. 2(c), Pt nanoparticles were
uniformly dispersed on the SiC–C surface for the fresh Pt/SiC–C
catalyst. The Pt particle size distribution for the fresh Pt/SiC–C
catalyst was also displayed in Fig. 2(d). Accordingly, the Pt
particle size for the fresh Pt/SiC–C catalyst varied in the range of
1.4–2.8 nm and the average Pt particle size was 2.1 nm with
52.3% dispersion.
Catalytic performance of the Pt/SiC–C catalyst
With high and uniform dispersion of Pt nanoparticles on SiC–C
composites, the Pt/SiC–C catalyst was anticipated to work well
in the liquid-phase hydrogenation of CAL. We rstly investi-
gated the kinetic proles of selective hydrogenation of CAL with
the Pt/SiC–C catalyst at different temperatures. As revealed in
Fig. 3(a), when the reaction was conducted at 25 ꢀC, a 32.8%
conversion was obtained within an initial 15 min. The
Table 1 Relevant physico-chemical parameters of the nanoporous
SiC–C composites and the Pt/SiC–C catalyst
Sample
SBET (m2 gÀ1
)
Vp (cm3 gÀ1
)
d (nm)
SiC–C
Pt/SiC–C
334
346
0.51
0.52
3.6
3.6
Fig.
1 (a) XRD patterns and (b) nitrogen adsorption–desorption
isotherms of nanoporous SiC–C and Pt/SiC–C catalyst.
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Fig. 2 (a and b) SEM images of Pt/SiC–C catalyst, (c and d) TEM image and Pt particle size distribution of fresh Pt/SiC–C catalyst, (e and f) TEM
image and Pt particle size distribution of the used Pt/SiC–C catalyst after 10 cycles.
conversion of CAL was gradually increased with reaction time selectivity to COL was not decreased with temperatures and as
and reached 84.9% aer 1 h as a result. Based on the conversion a result, about 80% selectivity to COL was still achieved by the
obtained within the initial 15 min, the activity (represented by Pt/SiC–C catalyst.
TOF, dened as the number of moles of converted CAL per mole
In order to further investigate the temperature effect on
of Pt active sites per hour) could reach 2446 hÀ1. It is worth selectivity to COL, the reaction was conducted at elevated
noting that COL was the primary product with about 80% temperatures. As clearly displayed in Fig. 3(b), although the
selectivity during the whole process. In order to evaluate conversion was further increased with the temperature, the
temperature effect on the selective hydrogenation of CAL, the selectivity to COL was still kept about 80%. That is, the reaction
reaction was also investigated with the Pt/SiC–C catalyst at 40 temperature only inuenced the reaction activity and the
ꢀC. Undoubtedly, the reaction went slightly faster at 40 ꢀC when conversion of CAL was almost linearly increased with temper-
compared with that conducted at 25 ꢀC. A 50.2% conversion was ature, while the selectivity to COL was independent of the
afforded within an initial 15 min, and almost complete temperature. Even at 80 ꢀC, the selectivity to COL was also
conversion of CAL was achieved aer 1 h at 40 ꢀC. Although the around 80%. Nevertheless, taking operating cost into account,
conversion of CAL was obviously increased with the tempera- in the following studies, room temperature (25 ꢀC) was still
ture and the TOF could reach 3745 hÀ1 at 40 ꢀC, it seemed that adopted as the standard reaction conditions. In addition,
the selectivity to COL was independent of the reaction temper- according to the results obtained with the Pt/SiC–C catalyst at
ature. That is, even the temperature was increased to 40 ꢀC, the different temperatures, the Pt/SiC–C catalyst was very active and
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Fig. 4 (a) Conversions and selectivity obtained with Pt catalysts sup-
ported on different materials and (b) the products distribution obtained
on monometallic Pt catalysts supported on different materials toward
the liquid-phase hydrogenation of CAL at room temperature. 5 wt% Pt/
C and Pt/Al2O3 were purchased from Alfa Aesar and other 5 wt% Pt
catalysts were prepared using a same method as the Pt/SiC–C catalyst.
Reaction conditions: 0.03 g Pt catalyst, 20 mL solvent (18 mL iso-
propanol and 2 mL water), 960 mL CAL, 2.0 MPa H2, 25 ꢀC, 1200 rpm, 1 h.
Fig. 3 (a) Kinetic profiles of liquid-phase selective hydrogenation of
CAL with Pt/SiC–C catalyst at 25 ꢀC and 40 ꢀC, respectively. Reaction
conditions: 0.03 g Pt catalyst, 20 mL solvent (18 mL isopropanol and 2
mL water), 960 mL CAL, 2.0 MPa H2, 1200 rpm. (b) Temperature effect
on liquid-phase hydrogenation of CAL. Reaction conditions: 0.03 g Pt
catalyst, 20 mL solvent (18 mL isopropanol and 2 mL water), 960 mL
CAL, 2.0 MPa H2, 1200 rpm, 1 h.
highly selective for the liquid-phase hydrogenation of CAL, even the similar method and investigated for the tested reaction. The
at room temperature. commercial 5 wt% Pt/C and Pt/Al2O3 catalysts purchased from
On the contrary, when we made a literature survey about the Alfa Aesar were also applied as reference catalysts.
liquid-phase selective hydrogenation of CAL, we noticed that As shown in Fig. 4(a), the conversion and selectivity to the
the similar reaction was usually performed at relatively higher desired product COL varied with different materials for loading
temperatures (40–95 ꢀC).22–29,33 Even those reactions were per- Pt nanoparticles. The conversion of CAL increased with the
formed at higher temperatures, most results including activity order: Pt/SBA-15 < Pt/S16-C z Pt/C z Pt/Al2O3 < Pt/CMK-3 < Pt/
and selectivity to COL obtained in literatures were lower than SiC–C. Among the Pt catalysts tested for this study, the nano-
those we obtained with the Pt/SiC–C catalyst even at room porous SiC–C composites supported Pt catalyst was most active
temperature in this study. Moreover, many researches demon- under the same conditions. As for the selectivity to COL affor-
strated that the monometallic Pt catalysts were seldom selective ded by different Pt catalysts, the sequence follows the order as:
for the hydrogenation of C]O bond due to thermodynamic Pt/Al2O3 < Pt/CMK-3 < Pt/SBA-15 z Pt/S16-C < Pt/C < Pt/SiC–C.
reason.21 In order to compare the catalytic performance of The Pt/SBA-15 and Pt/S16-C catalysts gave comparable selec-
monometallic Pt catalysts supported on different materials for tivity to COL and HCAL (hydrocinnamaldehyde), suggesting
the selective hydrogenation of CAL under our tested conditions, that the Pt/SBA-15 and Pt/S16-C were not selective either for
5 wt% Pt catalysts supported on other materials, such as C]O bond or for C]C bond hydrogenation. While for the Pt/
ordered mesoporous silica SBA-15, ordered mesoporous carbon CMK-3 and Pt/Al2O3 catalysts, they were selective for C]C
CMK-3 replicated from SBA-15 silica, and ordered mesoporous bond hydrogenation and the main product HCAL was afforded.
carbon S16-C replicated from SBA-16 silica, were prepared using Although simultaneous hydrogenation of both C]O and C]C
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double bond was inevitable because HCOL (hydrocinnamyl
alcohol) was also detected on each Pt catalyst supported on
whatever material, the content of HCOL was low. For clarity,
Fig. 4(b) shows the product distribution obtained with different
Pt catalysts under the same conditions. As can be clearly seen,
the Pt/SiC–C catalyst gave the prominent product COL, while
CAL, HCAL and HCOL are minor components. For other Pt
catalysts supported on silica, carbon or Al2O3, there was no
priority in product distribution.
Further characterization of the Pt/SiC–C catalyst using XPS
It suggests that monometallic Pt catalysts supported on tradi-
tional supports such as carbon, silica and alumina are indeed
unselective for the liquid-phase hydrogenation of CAL; while
the monometallic Pt catalyst supported on SiC–C composites is
not only active, but also highly selective for production of COL
during the liquid-phase hydrogenation of CAL. To explain the
superiority of nanoporous SiC–C composites supported Pt
catalyst towards the selective hydrogenation of CAL, the Pt/SiC–
C catalyst was further characterized using XPS aer in situ pre-
treated in owing hydrogen at 400 ꢀC for 1 h in a reactor
attachment of the XPS spectrometer. For C1s spectrum of Pt/
SiC–C catalyst, the binding energy (BE) at 283.1 eV could be
ascribed to C–Si of SiC, while the BE at 284.4 eV undoubtedly
belongs to C–C of amorphous carbon. In addition, there was
trace amount of oxygen-containing groups on SiC–C composite
surface (Fig. 5(a)). As for Si species on SiC–C composite surface,
Si–C species are dominant on the surface, in accompany with
Fig. 6 The reusability of the Pt/SiC–C catalyst toward the liquid-phase
hydrogenation of CAL. Reaction conditions: 0.03 g Pt/SiC–C catalyst,
20 mL solvent (18 mL isopropanol and 2 mL water), 960 mL CAL, 2.0
MPa H2, 25 ꢀC, 1200 rpm, 1 h.
a little silica (Fig. 5(b)). The Pt4f spectrum could be deconvo-
luted to three Pt species (Fig. 5(c)). The BE of 71.2 eV could be
assigned to 4f7/2 of Pt0 species, while 72.0 eV and 74.0 eV were
ascribed to 4f7/2 of Pt2+ and Pt4+ species, respectively.
Based on the Pt4f characterization results, although Pt0
species were dominant, there were still quite a few Pt species
with high valences Ptd+ (Pt2+ or Pt4+) on the Pt/SiC–C surface. It
should be emphasized that the sample had been in situ pre-
Fig. 5 (a) C1s XPS, (b) Si2p XPS, (c) Pt4f XPS spectra of Pt/SiC–C catalyst and (d) the hypothesis for CAL adsorption and activation with the Pt/SiC–
C catalyst.
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treated under a owing hydrogen atmosphere aer reduction in particular note is that the Pt/SiC–C catalyst could be easily
an aqueous solution of sodium formate. This veries that there recycled for at least 10 runs without any loss in activity or
is strong interaction between Pt species and the SiC–C selectivity to the desired product. The leached Pt amount in the
composites and the electron transfer occurs from Pt species to ltrate was below the detection limit of ICP-AES. The Pt nano-
SiC–C composites. We deduce that the Pt species with positive particles were still well dispersed on the support surface even
charge would be benecial for preferential adsorption of aer 10 reaction runs. It is deduced that the Pt particles with
carbonyl bond of CAL via electrostatic interaction between Ptd+ positive charges, derived from strong interaction between Pt
species and carbonyl oxygen atom, so that the activation of particles and SiC–C composites, are benecial for preferential
carbonyl bond was improved. Meanwhile, hydrogen atoms via adsorption and activation of carbonyl bond of CAL via electro-
dissociative adsorption on Pt0 species can attack the activated static interaction between oxygen atoms of carbonyl group and
carbonyl group of CAL to form the desired product COL. As Pt species with positive charges.
a result, high selectivity to COL was afforded with the Pt/SiC–C
catalyst. The hypothesis for adsorption, activation and hydro-
genation of C]O double bond of CAL was also proposed in
Fig. 5(d).
Acknowledgements
The research was nancially supported by the National Natural
Science Foundation of China (Grant Nos. 21273076 and
Reusability of the Pt/SiC–C catalyst
21373089), the Open Research Fund of Top Key Discipline of
Chemistry in Zhejiang Provincial Colleges and Key Laboratory
of the Ministry of Education for Catalysis Materials (Zhejiang
Normal University) (ZJHX2013), and Shanghai Leading Project
(B409).
The reusability is one of the important matters to be considered
for a heterogeneous catalyst involved in a liquid-phase reaction.
Therefore, we investigated the reusability of the Pt/SiC–C cata-
lyst toward the liquid-phase hydrogenation of CAL at room
temperature. Aer the reaction, the Pt/SiC–C catalyst was
ltered and washed using fresh solvent and then participated in
the next run. To our delight, the Pt/SiC–C catalyst can be easily
recovered and recycled for at least 10 runs without any loss in
activity or selectivity to COL (Fig. 6). Moreover, we noticed that
even higher CAL conversions and COL selectivity were fur-
nished with the used Pt/SiC–C catalyst aer the rst run.
Meanwhile, the selectivity to HCAL was suppressed as well (see
Fig. S4 for the detailed product distribution†). It can be inter-
preted by that the catalyst surface was reconstructed aer the
rst run and the catalyst surface was more suitable for the
selective hydrogenation of CAL to the desired product COL. We
also detected the ltrate using ICP-AES to ensure the hetero-
geneous reaction. As a result, the leached Pt amount was below
the detection limit of ICP-AES. This further demonstrates that
Pt nanoparticles supported on SiC–C surface are stable enough
during the recycling processes. In addition, we also character-
ized the used Pt/SiC–C catalyst using TEM. As already displayed
in Fig. 2(e), the Pt nanoparticles were still uniformly dispersed
on the SiC–C surface except that the Pt particles were slightly
aggregated aer 10 reaction cycles. According to the Pt particle
size distribution in Fig. 2(f), the Pt particle size of the used Pt/
SiC catalyst was centered in 2.2–2.6 nm, with an average Pt
particle size of 2.4 nm.
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