Graphite oxide-supported Karstedt catalyst for the hydrosilylation of olefins with triethoxysilane

Article abstract of DOI:10.1016/j.catcom.2013.10.043

A graphite oxide-supported Karstedt heterogeneous catalyst was synthesized from vinyltriethoxysilane via immobilization on graphite oxide, followed by reacting with chloroplatinic acid. The samples were characterized by FT-IR, TGA, ICP-AES, XRD and TEM te

Full text of DOI:10.1016/j.catcom.2013.10.043

Catalysis Communications 46 (2014) 1–5
Contents lists available at ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short Communication
Graphite oxide-supported Karstedt catalyst for the hydrosilylation of
olefins with triethoxysilane
⁎
⁎
Fuyuan Rao, Shengjun Deng , Chao Chen, Ning Zhang
Department of Chemistry, Nanchang University, Nanchang 330031, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 29 August 2013
Received in revised form 28 October 2013
Accepted 29 October 2013
Available online 21 November 2013
A graphite oxide-supported Karstedt heterogeneous catalyst was synthesized from vinyltriethoxysilane via
immobilization on graphite oxide, followed by reacting with chloroplatinic acid. The samples were characterized
by FT-IR, TGA, ICP-AES, XRD and TEM techniques. The catalyst was active for hydrosilylation of olefins with
triethoxysilane and showed good recoverability without significant loss in activity and selectivity within succes-
sive runs.
© 2013 Elsevier B.V. All rights reserved.
Keywords:
Graphite oxide
Karstedt's catalyst
Hydrosilylation
Heterogeneous catalyst
Pt
1. Introduction
catalyst on GO might afford an efficient, reusable and environmentally
benign catalyst for hydrosilylation.
Hydrosilylation is an important organic transformation for the
construction of Si\C bonds and plays a vital role in the synthesis of
functional silanes and silicon polymers [1]. Generally, transition metal
complexes are known to be efficient catalysts for the hydrosilylation
reaction [2], in particular the Pt based catalysts; Karstedt's catalyst,
characterized with C_C group coordination to Pt, is one of the most ef-
ficient homogeneous industrial catalysts [3]. However, the homogenous
catalyst suffers from some drawbacks such as deactivation and difficult
recovery and recycling of the catalyst. Consequently, development of
efficient solid-based heterogeneous catalyst for hydrosilylation reac-
tion is highly desirable due to its easy separation, reusability and
environment-friendly. The solid immobile materials included silica
[4–7], glass fiber [8], MCM-41 [9], and organic polymers [10–13]. Ba-
sically, the support has to be thermally and chemically stable during
the reaction process and has to provide accessibility and a good dis-
persion of the active sites.
Graphite oxide (GO), one of the most important derivatives of
graphene, is an inexpensive, stable and extraordinarily versatile carbon
material [14]. Specifically, due to the various oxygen containing
functional groups (hydroxyl, carboxyl, and epoxy groups) attached
to carbons or at the edges of the layer [15], GO surface can be easily
modified with compounds containing active groups [16–18]. Therefore,
GO performs as an excellent supporting material for immobilizing
homogenous catalysts. These suggest that immobilizing Karstedt's
Herein, we report the preparation and characterization of the
intercalated GO composites modified with vinyltriethoxysilane
(VTEO) to be used as host to further attach the catalytic Pt complex.
The catalytic performance of the prepared hybrid catalysts was tested
in the hydrosilylation of olefins with triethoxysilane.
2. Experiment
2.1. Preparation of the catalyst
2.1.1. Preparation of GO
GO was prepared by graphite powder based on a modified Hummers
method [19]. Graphite powder (3 g, 8000 mesh) was added to an 80 °C
solution containing concentrated H2SO4 (12 mL), K2S2O8 (2.5 g), and
P2O5 (2.5 g), stirred at 80 °C for 6 h, and then diluted with ultrapure
water (500 mL). The mixture was filtered and washed with ultrapure
water, and dried at 50 °C overnight. This pre-oxidized graphite was
put into cold concentrated H2SO4 (120 mL), and then KMnO4 (15 g)
was added gradually under stirring, and kept to be below 20 °C by
cooling. Successively, the mixture was stirred at 35 °C for 2 h, and
then diluted with 250 mL of ultrapure water (below 50 °C). The mix-
ture was stirred for another 2 h, and then additional ultrapure water
(750 mL) was added. 30% H2O2 (20 mL) was added to the mixture,
after which the color of mixture changed into brilliant yellow. The
mixture was filtered and washed with 1:10 HCl aqueous solution
(1 L) to remove metal ions followed by abundant water to remove
the acid. The product was dried at 40 °C overnight under vacuum.
⁎
Corresponding authors. Tel./fax: +86 791 83969514.
E-mail addresses: dshj1028@126.com (S. Deng), nzhang.ncu@163.com (N. Zhang).
1566-7367/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.catcom.2013.10.043

2
F. Rao et al. / Catalysis Communications 46 (2014) 1–5
2.1.2. Preparation of functionalized GO with VTEO (GO-VTEO)
GO (3 g) was dispersed in N-methylpyrrolidone (300 mL) under
ultrasonication for 1 h. After further addition of VTEO (3 mL), the
mixture was stirred at 110 °C for 24 h. The product was purified
gradually by centrifugation in methanol, water, and acetone, and fi-
nally dried at 80 °C overnight under vacuum.
3. Result and discussion
3.1. Characterization
Scheme 1 displays the design and synthesis process of the GO-
Karstedt catalyst. The reaction of GO with the organosilane is likely
to take place through hydrolysis/condensation of the carboxyl and
surface hydroxyl functional groups of GO and the hydrolyzed ethoxy
groups of VTEO, and the vinyl groups of VTEO are the anchoring sites
for Pt complexes.
2.1.3. Preparation of GO-Karstedt catalyst
GO-VTEO (2 g) was added to a solution containing NaHCO3
(0.032 g), H2PtCl6·H2O (0.05 g) and ethanol (120 mL), stirred at
40 °C for 24 h, filtered, washed with 6 × 40 mL of ethanol, and
dried at 70 °C overnight under vacuum. The content of platinum in
catalyst was 0.89% by ICP-AES detection. For comparison, the
chloroplatinic acid was directly supported on the rGO which was
prepared by directly reducing GO (Supplementary data), denoted
as rGO-Pt catalyst.
First of all, the chemical changes occurring upon the treatment of
VTEO can be observed by FT-IR spectra (Fig. 1A). The most character-
istic features in the FT-IR spectra of GO are the O\H stretching at
3372 cm−1 and deformation vibration at 1404 cm−1, the C_O car-
bonyl stretching at 1727 cm−1, and the C\OH or the C\O stretching
at 1221 and 1047 cm−1. The resonance at 1615 cm−1 can be assigned
to the vibrations of the adsorbed water molecules [20]. Upon treatment
with VTEO, the condensation between the organosilane and the surface
hydroxyl groups as seen by the changes in the 1250–1000 cm−1 region
where contribution of both Si\O\C and Si\O from the silanol groups
is observed. The new band at 1578 cm−1 can be assigned to stretching vi-
bration of C_C bonds in VTEO moieties [21]. For GO-Karstedt, due to the
complex interaction between Pt and vinyl group of VTEO, stretching
vibration of C_C bonds causes a low-field shift (1560 cm−1) [22].
Moreover, the content of platinum in catalyst was 0.89% by ICP-AES
analysis. These results indicate the successful introduction of Pt.
Fig. 1B illustrates TGA curves for GO-Karstedt catalyst and interme-
diate products under nitrogen atmosphere. GO shows about 15% weight
loss near 100 °C, evidently owing to evaporation of water molecules
which are held in the material. Two other significant mass losses
are observed in the range of 150–280 and 500–750 °C, corresponding
to the removal of the labile oxygen-containing functional groups and
pyrolysis of the carbon skeleton of GO, respectively [16,23]. Compared
to the GO curve, the weight loss of GO-VTEO and GO-Karstedt catalysts
around 100 °C is much lower, indicating that graphene oxide sheets ex-
hibit high hydrophobicity upon silanization of VTEO [8]. Moreover, GO-
VTEO and GO-Karstedt catalysts show another two obvious weight
losses. The first loss is in the range of 150–220 °C attributed to the de-
composition of undigested oxygen carrying functionalities which have
not participated in interaction with VTEO. The other major mass loss
2.2. Characterization techniques
FT-IR spectra were recorded on a Nicolet 5700 spectrometer, with
samples being dispersed on KBr disks. Inductively coupled plasma
atomic emission spectroscopy (ICP-AES) analysis was conducted on
a PerkinElmer OPTIMA 5300DV emission spectrometer. Thermogra-
vimetric analysis (TGA) was carried out on a SDT Q600 instrument
with a heating rate of 10 °C·min−1 under nitrogen atmosphere.
Powder X-ray diffraction (XRD) was conducted on a TD-3500 diffrac-
tometer with filtered Cu Kα radiation (λ = 1.5406 Å) at 40 kV and
30 mA. Transmission electron microscopic (TEM) studies were ob-
tained on a JEOL JEM-2100 transmission electron microscope.
2.3. Catalytic tests
Typical hydrosilylation reaction procedures were as follows: GO-
Karstedt catalyst (0.83 × 10−3 mmol Pt) was added to a 10 mL
round bottomed flask equipped with a magnetic stirrer, and the olefin
(5.0 mmol) and triethoxysilane (5.0 mmol) were then added. The reac-
tion mixture was then stirred at 60 °C for 180 min. Hydrosilylation
products were separated from the catalyst by decantation and the con-
version of olefin and the selectivity were determined by GC–MS using a
25 m × 0.32 mm × 0.5 μm column.
Scheme 1. Proposed view for the construction of GO-Karstedt.

F. Rao et al. / Catalysis Communications 46 (2014) 1–5
3
is in the range of 220–580 °C resulting from the pyrolysis of VTEO
moieties [23].
The X-ray diffraction patterns of pristine graphite, GO, GO-VTEO
and GO-Karstedt are shown in Fig. 2A. Pristine graphite exhibits a
typical sharp (002) peak at 2θ = 26.5° with a d spacing of 0.34 nm.
The GO pattern shows a characteristic peak at 2θ = 9.0°, with a cor-
responding d spacing of 0.98 nm, attributed to the interlayer space
between typical graphene oxide sheets needed to accommodate
the water molecules trapped between oxygen-containing functional
groups on graphene oxide sheets. Compared to the starting GO, the
diffraction peak of GO-VTEO shifts to a higher angle (2θ = 10.0°) corre-
sponding to smaller interlayer distance (0.88 nm), which is due to the
less hydrophilicity after functionalization [16]. The GO-Karstedt pattern
exhibits a peak at 2θ = 11.1°, which asserts for a further decrease of the
interlayer distance (0.80 nm). We suggest that the introduction of Pt
into GO-VTEO narrowed the distance of graphene oxide sheets by the
coordination between Pt and the C_C bonds of VTEO moieties.
Fig. 2B shows the TEM images of GO and GO-Karstedt. GO appears
partially transparent with typical large crumpled thin flakes. GO-
Karstedt shows that the immobilized complexes of Pt catalyst have a
layered structure. It can be seen that the crumpled nanosheets are in
an agglomerated phase [24].
3.2. Catalytic experiments
The prepared GO-Karstedt catalyst was tested in the hydrosilylation
of olefins with triethoxysilane. Initially, we studied the catalytic activity
at different temperatures using the hydrosilylation of 1-octene with
triethoxysilane as the model reaction (Fig. 3). It was found that GO-
Karstedt catalyst exhibited high catalytic activity; over 90% yield in
favor of β-adduct could be obtained from 40 to 70 °C within 120 min,
and the reaction rate raised with the increasing of temperature. Notice-
ably, when the reaction was carried out at 60 °C, octyltriethoxysilane
was obtained in 90.4% yield after 60 min. Catalyst leaching experiments
of GO-Karstedt have been performed by hot filtration of the reaction
mixture and subsequent testing of the catalytic activity of the filtrate
for hydrosilylation without addition of a catalyst, and no further reac-
tion was observed for the solution following filtration. Also, a control ex-
periment was conducted using a rGO-Pt catalyst, and only 74.9% yield of
Fig. 1. (A) FT-IR spectra and (B) TGA curves for (a) GO, (b) GO-VTEO and (c) GO-Karstedt.
Fig. 2. (A) XRD patterns for (a) graphite, (b) GO, (c) GO-VTEO and (d) GO-Karstedt; (B) TEM images for (a) GO and (b) GO-Karstedt.

4
F. Rao et al. / Catalysis Communications 46 (2014) 1–5
Fig. 4. Catalyst activity of reused GO-Karstedt catalyst for the hydrosilylation of 1-octene
with triethoxysilane. : Conversion of 1-octene; : Yield of octyltriethoxysilane.
Fig. 3. Effect of reaction temperature on the yield of octyltriethoxysilane. Reaction conditions:
1-octene = 5.0 mmol, triethoxysilane = 5.0 mmol, catalyst = 0.83 × 10−3 mmol Pt.
high operational stability with no dramatic loss of catalytic activity
and selectivity even after seven successive times. When using rGO-
Pt as catalyst, the catalytic activity decreased significantly, and
almost no reaction for the hydrosilylation of 1-octene with
triethoxysilane after four cycles (Fig. S1).
octyltriethoxysilane was obtained after 180 min (Supplementary data),
which shows that the rGO-Pt catalyst was not so effective for the
hydrosilylation of olefins with triethoxysilane. The results indicate
that vinyl groups of GO-Karstedt catalyst may play an important
role to convert H2PtCl6 to Pt(0)-olefin complexes, which make GO-
Karstedt catalyst more active [25].
To examine the substrate scope of GO-Karstedt catalyst, the
hydrosilylation reaction was extended to several substituted olefins
with triethoxysilane, and the catalytic results are listed in Table 1.
In all cases, GO-Karstedt catalyst exhibits positive catalytic activity,
and the substituted olefins were smoothly converted to their corre-
sponding products. For the aliphatic olefins (entries 1–3), excellent
conversion (over 97.8%) and selectivity (over 92.4%) were attained
in all cases, indicating that the catalyst has a high activity for the
hydrosilylation reaction. Unfortunately, when aromatic olefins
were used as the substrates (entries 4–6), the β-adduct selectivity
decreased significantly, although the catalyst exhibited high conver-
sion of olefins, which results from the steric hindrance of substituted
olefins [26].
4. Conclusion
Graphite oxide has been studied for the first time as a support of
Karstedt catalyst and applied in hydrosilylation reaction. The results
show that the catalyst was active for hydrosilylation of olefins with
triethoxysilane, in particular for the aliphatic with triethoxysilane. Fur-
thermore, the catalyst shows a good recoverability and can be recycled
seven times without significant loss of catalytic activity and selectivity.
These results imply that GO is a superior support for immobilizing com-
plex catalysts.
Acknowledgments
This work was supported by the National Natural Science Founda-
tion of China (No. 21062013), the Science and Technology Support Pro-
gram of Jiangxi Province (No. 2010ZDG05900), and the Foundation of
Educational Department of Jiangxi Province (GJJ11012).
The stability of the catalyst is an important aspect of any industri-
al application. Therefore we tested the reusability of GO-Karstedt
catalyst in the hydrosilylation of 1-octene with triethoxysilane at
60 °C. For each cycle of the test, solution was decanted completely,
leaving the catalyst powder on the bottom of the reaction vessel.
The same amounts of the substrates were recharged, and the next
cycle started. As shown in Fig. 4, GO-Karstedt catalyst exhibited a
Appendix A. Supplementary data
Supplementary data to this article can be found online at http://dx.
doi.org/10.1016/j.catcom.2013.10.043.
Table 1
Catalytic activity of GO-Karstedt for the hydrosilylation reaction of olefins with triethoxysilane.a
Entry
Olefin
Time (min)
Conv.b (%)
Selectivity (%)
TOF (h−1
)
β
α
Alkane, etc.
1
2
3
4
5
6
1-Hexene
1-Octene
1-Decene
Styrene
p-Methylstyrene
p-Chlorostyrene
90
60
60
100
120
120
100
92.5
92.4
92.4
67.2
58.9
53.1
Trace
Trace
Trace
28.9
36.0
41.9
7.5
7.6
7.6
3.9
5.1
5.0
10340
9875
9968
8757
4098
4844
97.8
98.0
94.9
79.3
97.8
a
Reaction conditions: olefin = 5.0 mmol, triethoxysilane = 5.0 mmol, catalyst = 0.83 × 10−3 mmol Pt, and temperature = 60 °C.
No increase in conversion with increasing reaction time.
b

F. Rao et al. / Catalysis Communications 46 (2014) 1–5
5
[14] Y. Zhu, S. Murali, W. Cai, X. Li, J.W. Suk, J.R. Potts, R.S. Ruoff, Adv. Mater. 22 (2010)
3906–3924.
References
[15] H. He, J. Klinowski, M. Forster, A. Lerf, Chem. Phys. Lett. 287 (1998) 53–56.
[16] A. Guimont, E. Beyou, G. Martin, P. Sonntag, P. Cassagnau, Macromolecules 44
(2011) 3893–3900.
[17] D. Chen, H. Feng, J. Li, Chem. Rev. 112 (2012) 6027–6053.
[18] A.B. Dongil, B. Bachiller-Baeza, A. Guerrero-Ruiz, I. Rodríguez-Ramos, Catal.
Commun. 26 (2012) 149–154.
[1] I. Ojima, S. Patai, Z. Rappaport, in: Z. Rappaport (Ed.), The Chemistry of Organic
Silicon Compounds, Wiley-Interscience, New York, 1989, (Chapter 25).
[2] B. Marciniec, J. Gulinski, Z.W. Kornetka, in: B. Marciniec (Ed.), Comprehensive Hand-
book on Hydrosilylation, Pergamon Press, Oxford, UK, 1992, (Chapter 2).
[3] B.D. Karstedt, US Patent 3775452, 1973.
[4] Q.J. Miao, Z.P. Fang, G.P. Cai, Catal. Commun. 4 (2003) 637–639.
[5] Z.M. Michalska, Ł. Rogalski, K. Rózga-Wijas, J. Chojnowski, W. Fortuniak, M.
Ścibiorek, J. Mol. Catal. A Chem. 208 (2004) 187–194.
[6] G. Liu, B. Huang, M. Cai, React. Funct. Polym. 67 (2007) 294–298.
[7] J. Li, C. Yang, L. Zhang, T. Ma, J. Organomet. Chem. 696 (2011) 1845–1849.
[8] H.T. Yang, Z.P. Fang, X.Y. Fu, L.F. Tong, Catal. Commun. 9 (2008) 1092–1095.
[9] R. Hu, L. Zha, M. Cai, Catal. Commun. 11 (2010) 563–566.
[10] R. Drake, R. Dunn, D.C. Sherrington, S.J. Thomson, J. Mol. Catal. A Chem. 177 (2001)
49–69.
[19] N.I. Kovtyukhova, P.J. Ollivier, B.R. Martin, T.E. Mallouk, S.A. Chizhik, E.V. Buzaneva,
A.D. Gorchinskiy, Chem. Mater. 11 (1999) 771–778.
[20] T. Szabó, O. Berkesi, I. Dékány, Carbon 43 (2005) 3186–3189.
[21] Y. Matsuo, Y. Nishino, T. Fukutsuka, Y. Sugie, Carbon 45 (2007) 1384–1390.
[22] J. Li, J. Peng, Y. Bai, G. Zhang, G. Lai, X. Li, J. Organomet. Chem. 695 (2010) 431–436.
[23] H. Yang, F. Li, C. Shan, D. Han, Q. Zhang, L. Niu, A. Ivaska, J. Mater. Chem. 19 (2009)
4632–4638.
[24] H.P. Mungse, S. Verma, N. Kumar, B. Sain, O.P. Khatri, J. Mater. Chem. 22 (2012)
5427–5433.
[11] R. Drake, D.C. Sherrington, S.J. Thomson, J. Chem. Soc. Perkin Trans. 1 (2002)
1523–1534.
[25] L.N. Lewis, R.E. Colborn, H. Grade, G.L. Bryant, C.A. Sumpter, R.A. Scott, Organometal-
lics 14 (1995) 2202–2213.
[12] Y. Bai, J. Peng, Y. Hu, J. Li, G. Lai, J. Fluor. Chem. 132 (2011) 123–127.
[13] R. Drake, D.C. Sherrington, S.J. Thomson, React. Funct. Polym. 60 (2004) 65–75.
[26] M. Konkol, M. Kondracka, P. Voth, T.P. Spaniol, J. Okuda, Organometallics 27 (2008)
3774–3784.