Supporting Information for
Core-Shell-Shell Microsphere Catalysts Containing Au Nanoparticles for Styrene
Epoxidation
Sayantani Das1 and Tewodros Asefa1,2,*
1 – Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey,
610 Taylor Road, Piscataway, NJ 08854, USA
2 – Department of Chemical and Biochemical Engineering, Rutgers, The State University of New
Jersey, Piscataway, NJ 08854, USA
* Corresponding author: tasefa@rci.rutgers.edu
Table S1. Control reaction of styrene oxidation in TBHP and toluene at different temperatures without
using a catalyst.
Entry
Temperature
(°C)
Time
(h)
% Conversion of
styrene
% Selectivity to
Benzaldehyde
% Selectivity to
Styrene Oxide
1
RT
24
6
~100
0
2
50
24
13
~100
0
3
80
24
66
53
13
Table S2. Elemental analysis obtained with ICP-AES of Au in the recycled catalysts as well as in the
reaction mixtures. The result was used to determine if AuNPs leached from the porous SiO2-AuNP-SiO2
catalyst into the reaction mixtures.
Entry
Au (ppm)
Au (%)
Au (mmol)
Catalyst
7632
0.76
2.4 x 10-3
Catalyst after 3rd cycle
5368
0.54
2.18 x 10-3
7
0.01
4.05 x 10-5
Reaction solution recovered from 3rd cycle
a
a
The reaction solution recovered after the 3rd cycle.
Table S3. Comparison of the catalytic activity of our porous SiO2-AuNP-SiO2 microsphere catalyst in
styrene epoxidation reaction with those of other previously reported nanostructured catalysts in the
same reaction. The conditions used for the catalytic reactions are also listed. Although the conditions
are not exactly the same in all the cases, the results give some ideas on the relative effectiveness of our
catalyst with respect to others.
Catalyst
Oxidant
Reaction Condition
% Conv. of
Styrene
Selectivity towards
Epoxide
Ref.
79 % in 8 h
74%
[1]
> 90% after
>12 h
92%
[2]
70%
[3]
Catalyst = 0.1 g;
AuNP on layered
double hydroxide
TBHP
(28 mmol)
Styrene = 10 mmol;
T = 80 °C
Catalyst = 50 mg;
Au25 on
hydroxyapatite
TBHP
Styrene = 40 mg;
(200 mg)
T = 80 °C
Catalyst = 0.6 mg;
Thiolate protected
Au NP
27 % in
O2
Styrene = 12 mmol;
24 h
T = 100 °C
Catalyst = 10 mL;
AuNP stabilized by IL
m-CPBA
(15 mmol)
100 % in
Styrene = 5 mmol;
90%
[4]
92%
[5]
75%
[6]
69%
[7]
54%
[8]
> 80%
[9]
4h
T = 15 °C
Catalyst = 50 mg;
AuNP organic
inorganic hybrid
mesoporous silica
H2O2
(20 mmol)
Au-PMO-SBA15
TBHP
(15.4
mmol)
Au-meso-Al2O3
Styrene = 10 mmol;
50 % in 6 h
T = 70 °C
TBHP
(15.4
mmol)
Catalyst = 0.1 g;
95 % in
Styrene = 10 mmol;
12 h
T = 80 °C
Catalyst = 0.1 g;
84% in
Styrene = 10 mmol;
12 h
T = 80 °C
Catalyst = 0.1 g;
AuNP on MgO
TBHP
(15 mmol)
Styrene = 10 mmol;
62 % in 3 h
T = 80 °C
Fe3O4@SiO2Au@mSiO2
Microspheres
Catalyst = 0.1 g;
TBHP
(38 mmol)
72% in
Styrene = 10 mmol;
40 h
T = 82 °C
Catalyst = 0.025 g;
100% in
This work
TBHP
Styrene = 1 mmol;
61%
-
56%
-
10 h
T = 80 °C
This work
(porous SiO2-AuNPSiO2 microsphere
catalyst)
Catalyst = 0.025 g;
75% in
TBHP
Styrene = 1 mmol;
5h
T = 80 °C
SiO2 Microspheres
SiO2
% Transmittance
160
SiO2-NH2 Microspheres
SiO2-NH2
120
80
40
0
400
1400
2400
3400
Wavenumber ( cm-1)
Wavenumber ()
Figure S1. FT-IR spectra of SiO2 and amine-functionalized SiO2 (SiO2-NH2) microspheres. In both spectra,
many similar peaks were observed, as expected. These include a peak at ~1100 cm-1 corresponding to SiO-Si stretching and broad peaks at between 3000 – 3500 cm-1 corresponding to O-H and N-H bond
stretchings. Furthermore, the spectra show peaks corresponding to N-H or O-H bending at ~1555 cm-1.
More importantly however, the spectrum for SiO2-NH2 microspheres show a peak at ~900 cm-1 that
corresponds to N-H wagging, which is not observable in the spectrum for SiO2. The peaks are consistent
with that reported for SiO2 nanospheres and amine-functionalized silicas reported previously [10,11].
100
SiO2 Microspheres
SiO2
SiO2-NH2
SiO2-NH2 Microspheres
Weight %
96
92
88
84
0
200
400
Temperature (°C)
Temperature
600
800
Figure S2. Thermogravimetric traces of SiO2 and amine-functionalized SiO2 (SiO2-NH2) microspheres.
Figure S3. TEM image showing thick and non-uniform silica shells (indicated by red arrows) when a large
amount of TEOS was used for making the silica shells around the SiO2-AuNP core-shell microspheres.
% Conversion of Styrene
100
80
60
1st Cycle
2nd Cycle
40
3rd Cycle
20
0
0
5
10
Time (h)
Figure S4. % Conversion versus time graphs for styrene epoxidation reaction catalyzed by porous SiO2AuNPs-SiO2 microsphere catalysts. The result shows that the catalytic activity of the materials remained
reasonably unchanged at least during three catalytic cycles.
120%
% Conversion of Styrene
100%
80%
60%
40%
SiO2-Au
SiO2-Au
20%
Used
SiO2-Au
Recycled
SiO2-Au
0%
0
2
4
6
8
10
Time (h)
Figure S5. % Conversion versus time graphs for styrene epoxidation reaction catalyzed by SiO2/AuNPs
core-shell microsphere catalysts. The result shows a decrease in catalytic activity of the catalyst as a
result of aggregation of the nanoparticles in this material compared to the porous SiO2-AuNP-SiO2 coreshell-shell microspheres (see in Fig. S4).
Absorbance (a.u)
0.4
0.3
0.2
0.1
0
300
500
700
Wavelength (nm)
Figure S6. UV-Vis spectrum of recycled porous SiO2-AuNP-SiO2 core-shell-shell microspheres after three
reaction cycles. The spectrum shows the characteristic plasmon band of Au nanoparticles at around 530
nm, marked by an arrow. This result indicates the stability of the Au nanoparticles when confined in the
core-shell-shell microspheres. It also corroborates why the materials showed stable catalytic activity in
Fig S4 above.
References (for Supporting Information Section)
[1] F. Zhang, X. Zhao, C. Feng, B. Li, T. Chen, W. Lu, X. Lei, and S. Xu, ACS Catal. 1 (2011)
232.
[2] Y. Liu, H. Tsunoyama, T. Akita and T. Tsukuda, Chem. Commun. 46 (2010) 550.
[3] Y. Zhu, H. Qian, M. Zhu, and R. Jin, Adv. Mater. 22 (2010) 1915.
[4] L. Luo, N. Yu, R. Tan, Y. Jin, D. Yin and D. Yin, Catal. Lett. 130 (2009) 489.
[5] Y. Jin, D. Zhuang, N. Yu, H. Zhao, Y. Ding, L. Qin, J. Liu, D. Yin, H. Qiu , Z. Fu and D.
Yin, Microporous Mesoporous Mater. 126 (2009) 159.
[6] Y. Jin, P. Wang, D. Yin, J. Liu, H. Qiu, and N.Yu, Microporous Mesoporous Mater. 111
(2008) 569.
[7] D. Yin , L. Qin, J. Liu , C. Li and Y. Jin, J. Mol. Catal. A: Chem. 240 (2005) 40.
[8] N.S. Patil, B.S. Uphade, P. Jana, S.K. Bharagava, and V.R. Choudhary, Catal. Lett. 94
(2004) 89.
[9] Y. Deng, Y. Cai, Z. Sun, J. Liu, C. Liu, J. Wei, W. Li, C. Liu, Y. Wang, and D Zhao, J. Am.
Chem. Soc. 132 (2010) 8466.
[10] A. S. Maria Chong, and X. S. Zhao, J. Phys. Chem. B 107 (2003) 12650-12657.
[11] A. Beganskienė, V. Sirutkaitis, M. Kurtinaitienė, R. Juškėnas, and A. Kareiva, Mater. Sci.
10 2004) 287-290.