Selective reduction of 4,4′-dinitrostilbene-2,2′-disulfonic acid catalyzed by supported nano-sized gold with sodium formate as hydrogen source

Article abstract of DOI:10.1016/j.catcom.2010.12.006

Gold nanoparticles supported on four different metal oxides were prepared and applied in the chemoselective reduction of 4,4′-dinitrostilbene-2, 2′-disulfonic acid (DNS). With sodium formate as hydrogen source, > 99% of the DNS was transformed into 4,4′-diaminostilbene-2,2′- disulfonic acid (DSD) without the reduction of olefinic group, which uncovers a clean synthetic approach for useful amino substituted stilbene sulfonic acids.

Full text of DOI:10.1016/j.catcom.2010.12.006

Catalysis Communications 12 (2011) 568–572
Contents lists available at ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short Communication
Selective reduction of 4,4′-dinitrostilbene-2,2′-disulfonic acid catalyzed by supported
nano-sized gold with sodium formate as hydrogen source
a
a
a
b
a,
Wenchao Peng , Fengbao Zhang , Guoliang Zhang , Bo Liu , Xiaobin Fan ⁎
a
School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, People's Republic of China
Tianjin Academy of Environmental Sciences, People's Republic of China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 7 October 2010
Received in revised form 30 November 2010
Accepted 6 December 2010
Available online 13 December 2010
Gold nanoparticles supported on four different metal oxides were prepared and applied in the chemoselective
reduction of 4,4′-dinitrostilbene-2,2′-disulfonic acid (DNS). With sodium formate as hydrogen source, N99%
of the DNS was transformed into 4,4′-diaminostilbene-2,2′-disulfonic acid (DSD) without the reduction of
olefinic group, which uncovers a clean synthetic approach for useful amino substituted stilbene sulfonic acids.
©
2010 Elsevier B.V. All rights reserved.
Keywords:
Heterogeneous catalysis
Chemoselective
Reduction
Gold
Supported catalysts
1
. Introduction
,4′-Diaminostilbene-2,2′-disulfonic acid (DSD) is an important
effective in the reduction of aromatic nitro compounds containing
olefinic bonds catalyzed by Au NPs supported on TiO and Fe
2
2 3
O
4
[10,11]. Formates are also clean hydrogen source, and one of them
(ammonium formate) has also been used in the reduction of the nitro
compounds catalyzed by copper nanoparticles. However, the selec-
tivity for aromatic nitro compounds containing olefinic bonds was
only ~57% [12]. There is still no report about the reduction of DNS with
supported Au NPs as catalyst and sodium formate as reductant.
In this study, we prepared a serial of supported Au NPs catalysts
using the deposition–precipitation method with urea (DP urea) [13].
The chemoselectivity of these catalysts were investigated in the
reduction of DNS with sodium formate as hydrogen source. In addition,
the catalysts stability was also investigated, and activity can be restored
by calcination at 400 °C for 5 hours for a fourth recycle.
industrial intermediate widely used in production of direct dyes,
fluorescent brighteners and mothproofing agents [1]. It is usually
produced from the reduction of 4,4′-dinitrostilbene-2,2′-disulfonic
acid (DNS), and stoichiometric reducing agents, such as sodium
hydrosufite, iron, tin, or zinc in ammonium hydroxide have been
successfully applied in the reduction with high yields of ~98% [2–5].
However, these reducing agents are not environmentally sustainable,
and will generate lots of wastes [6]. Catalytic hydrogenation is a green
and effective way, but commercial catalysts, such as Raney Ni, will
reduce the olefinic group as well as the nitro group [7]. A catalyst of Pd
on C (Pd/C) can obtain better selectivity, but some additives are
needed during the reaction [8]. Therefore, the search for new facile,
chemoselective, and environmentally friendly procedures that avoid
the use of these hazardous stoichiometric reducing agents has
attracted substantial interest.
2. Experimental
2.1. Materials and reagents
The use of gold nanoparticles (Au NPs) supported on metal oxides
for organic reactions has attracted tremendous interest in recent
years, including addition of multiple C–C bonds, cyclization reactions,
rearrangements, C–C coupling reactions, oxidation reactions, and
hydrogenations [9]. In particular, the selective reduction of nitro
compounds in the presence of other reducible functions is more
challenging. The hydrogen and carbon monoxide have been proved
P25 titanium dioxide (ca. 80% anatase, 20% rutile; BET area ca.
2
−1
2 3
50 m g ) was obtained from Degussa Co. (Germany). α-Fe O (30 nm
2
−1
2 −1
2 3
BET area≥50 m g ), γ-Al O (10 nm, BET area≤200 m g ), and
−1
2
CeO (50 nm, BET area≤30 m g ) were obtained from Aladdin (China).
2
4,4′-dinitrostilbene-2,2′-disulfonic acid (DNS), 4,4′-diaminostilbene-2,2′-
disulfonic acid (DSD), 4,4′-diaminobibenzyl-2,2′-disulfonic acid (DAD)
and Raney Ni were provided by Huayu Chemical Company (Cangzhou,
China). Other chemical reagents and solvents (Merck) were either
analytical or chromatography grade and were used without further
purification.
⁎
Corresponding author.
E-mail address: xiaobinfan@tju.edu.cn (X. Fan).
1566-7367/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.catcom.2010.12.006

W. Peng et al. / Catalysis Communications 12 (2011) 568–572
569
2 2 2 3 2 3
Fig. 1. TEM images of Au/TiO (a), Au/CeO (b), Au/γ-Al O (c), and Au/α-Fe O (d).
2
.2. Catalyst preparation
2.4. Catalytic activity measurement
In the standard preparation conditions, 1 g nano-sized metal
oxides was added to 100 mL of an aqueous solution of HAuCl
The hydrogenation of DNS was performed in a 50 mL autoclave.
For each reaction, 10 mL H O, 0.05 g DNS and 0.3 g HCOONa were
4
2
−
3
(
8
0.9×10 M) and of urea (0.42 M). The suspension was heated to
0 °C and kept for 4 h with vigorous stirring. Then, the suspension was
charged into the autoclave together with 0.005 g catalyst. After
sealing the reactor, its air content was removed by flushing five times
with 5 bar nitrogen. Next, the autoclave was heated to 130 °C. After
5 hours, the reactants were taken out and analyzed by HPLC-ESI-MS.
The HPLC is Finnigan Surveyor HPLC integrated with quaternary
gradient pumps, photodiode array detector, auto injector, degasser
and system controller (all from Thermofisher Scientific, San Jose, CA,
USA). A reversed-phase Hypersil ODS-2 C18 column (250×4.6 mm i.d.,
separated from the precursor solution by centrifugation (15000 rpm
for 10 min). The obtained solids were washed to remove the residual
−
Cl , and were dried under vacuum at 100 °C for 3 h. After that, they
were calcined at 300 °C for 4 h and then reduced for 2 hours at 200 °C
in a flow of 5% H /Ar to obtain the final catalysts.
2
5
μm particle size) (ThermoScientific, US), with a guard column made of
the same packing material, was used for separation. HPLC conditions:
:95 acetonitrile: water—0.01 M ammonium acetate, 254 nm (flow:
2
.3. Catalyst characterization
5
−
1
Catalysts were examined by transmission electron microscopy
TEM) with a JEOL2010F microscope. The histograms of the Au NPs
1 mL min ).
(
size were established from the measurement of ~300 particles. The
size limit for the detection of the gold particle is 1 nm. The average
2.5. Catalyst stability
−
particle diameter d : was calculated from the following formula:
−
d = ∑nidi = ∑ni,where n
i
is the number of particles of diameter d
i
.
The catalyst stability was checked in the case of the Au/TiO2
system for the reduction of DNS. First, 0.02 g catalyst was used in a
40 mL reaction (fresh catalyst). The reaction was performed according
to Section 2.4. After finishing the reaction, the catalyst was recovered,
filtered and washed three times with distilled water. Then, they are
The actual Au weight loading of the samples were determined by the
inductively coupled plasma (ICP) technique, and the chemical state
of the Au species on the final catalysts was determined by X-ray
Photoelectron Spectroscopy (XPS).

570
W. Peng et al. / Catalysis Communications 12 (2011) 568–572
a
b 3
5
2
2
1
1
5
0
5
0
5
0
Au/TiO2
Au/CeO2
3
2
2
1
1
0
5
0
5
0
5
0
2
3
4
5
6
7
8
2
3
4
5
6
7
8
Partical size (nm)
Partical size (nm)
c
d
γ
Au/ -Al O
2 3
3
3
2
2
1
1
5
0
5
0
5
0
5
0
Au/
α
-Fe O3
2
4
3
2
1
0
0
0
0
0
2
3
4
5
6
7
2
3
4
5
6
7
Partical size (nm)
Partical size (nm)
2 2 2 3 2 3
Fig. 2. Size distributions of Au NPs in (a) Au/TiO , (b) Au/CeO , (c) Au/γ-Al O , and (d) Au/α-Fe O .
dried under vacuum at 100 °C for 2 h. After that, they were calcined at
00 °C for 5 h to obtain the 1st re-use bath. Second, 0.015 g 1st re-use
catalyst was used in a 30 mL reaction. Repeat the recovery process to
get the 2nd re-use bath. Then, 0.01 g 2nd re-use catalyst was used in a
Au NPs on Al
from 2 to 4 nm. While the other three catalysts had similar d (Au/TiO
4.7 nm, Au/CeO 4.8 nm, Au/Fe 4.6 nm), and the Au particles
mostly ranged from 4 to 6 nm. Because of the reduction process by
/Ar, the supported gold species are metallic states determined by
2 3
O was the smallest (3.8 nm), and they mostly ranged
−
4
2
2
2 3
O
2
0 mL reaction, and 0.005 g 3 rd re-use catalyst was used in a 10 mL
H
2
reaction. The reduction products of every recycle were analyzed by
HPLC system.
XPS (Fig. S1 in the Supporting Information). In addition, the gold
loadings of these catalysts were ~1.5% determined by ICP.
3.2. Reduction of DNS to DSD
3
. Results and discussion
Sodium formate is an important hydrogen source. It's very mild in
3
.1. Catalyst characterization
nature and conveniently available, and has been proved efficient
during hydrogenation of nitro compounds according to the following
reaction equation:
The catalysts were prepared using the deposition–precipitation
with urea (DP urea) method, which is suggested by Bond et al. [14]
and modified by Louis et al. [13]. Fig. 1 shows the TEM images of the
final catalysts, and size distributions of Au NPs on these catalysts are in
cat:
ArNO2 + 3HCOONa + H O → ArNH + 3NaHCO3
ð1Þ
2
2
2 3
Fig. 2. Among these four supports, Al O is non-reducible, and it is
different from other three reducible supports. Therefore, the dia-
meters of the Au NPs on these supports had some differences. The d of
It was shown that the reduction was preceded in the form of direct
hydrogen transfer between the sodium formate and the nitro acceptor
−
Fig. 3. The reduction of DNS to DSD and DAD.

W. Peng et al. / Catalysis Communications 12 (2011) 568–572
571
Table 1
4. Conclusion
Reduction of DNS with HCOONa by various catalysts.
Catalysts
—
xa
Au loading
wt.%)
Conv./%
Sel.
(DSD)/%
Sel.
(DAD)/%
V/mmol
Gold nanoparticles supported on four different metal oxides were
prepared and applied in the chemoselective reduction of DNS, and
HCOONa were selected as hydrogen source. Compared with the
conventional catalysts (Raney Ni) under the same temperature,
excellent selectivity (N99%) were obtained by the four Au NPs
containing catalysts. In addition, the catalyst's stability was also
investigated, and activity can be restored by calcination at 400 °C for
−
1
−1
(
h
g
Au/TiO2 — 4.7
1.7
1.6
1.5
1.6
100
100
100
100
100
N99.0
N99.0
N99.0
N99.0
0
b1.0
b1.0
b1.0
b1.0
N99.0
30
28
36
18
Au/Fe
Au/Al
Au/CeO
Raney Ni
2
O
3
— 4.6
— 3.8
— 4.8
2
O
3
2
aThe d−of Au NPs supported on each metal oxides.
5
hours for a fourth recycle.
rather than a dehydrogenation-hydrogenation sequence [15]. There-
fore, the selectivities during the catalysis reduction of DNS with
sodium formate should be different from that with hydrogen. The
above mentioned reduction of DNS with HCOONa (Fig. 3) catalyzed by
supported Au NPs was also investigated, and the results were listed in
Table 1. The determination of the reduction products was performed
by HPLC-ESI-MS, and the identification was further confirmed by
comparing their retention times with those of high purity standards
Acknowledgment
This work is supported by the National Natural Science Foundation
of China (No: 20776095) and the Program of Introducing Talents of
Discipline to Universities (China, No: B06006).
Appendix A. Supplementary data
(
Fig. S2 in the Supporting Information).
Perfect selectivities can be obtained during the reduction of DNS
Supplementary data to this article can be found online at
doi:10.1016/j.catcom.2010.12.006.
with HCOONa catalyzed by supported Au NPs, and all of the four
catalysts can provide selectivities of N99%. There are two reasons
resulting in the chemoselectivity between nitro and olefinic group:
(
1) the absorption of the nitro group to the supported gold catalysts is
a 120
preferential versus the carbon–carbon double bonds; (2) the intrinsic
rate for the reduction of the nitro group is much higher than that of
the olefinic group [16].
Non-Calcined
Calcined at 400 C
o
100
Table 1 also includes the rate of DSD formation (V) during the
reduction. The rate depends on the diameters of Au NPs and the
8
6
4
2
0
0
0
0
0
nature of supports. The Au NPs on Al
Au/Al showed the highest rate. For Au/TiO
diameter of Au NPs and BET areas of the supports are all similar, so
O
2 3
has the smallest diameter, so
2
O
3
2
and Au/Fe , the
2 3
O
2 2
they had similar rates. The BET area of CeO is the smallest, so Au/CeO
has the slowest rate.
It should be noted that formate acid and ammonium formate
might also be good hydrogen transfer agents by a similar mechanism.
However, formate acid has high corrosivity and ammonium formate
can be decomposed to hydrogen cyanide (HCN) and water easily at a
high temperature [15]. In addition, one commercial catalyst (Raney
Ni) with HCOONa as hydrogen source under the same temperature
was also investigated, and no DSD could be observed during the
reduction of DNS.
Fresh catalyst 1st Re-Use
2nd Re-Use
3rd Re-Use
Au/TiO2
b 1
20
Non-Calcined
o
3
.3. Catalyst stability
Calcined at 400 C
100
TiO
2
P25 is a commercial available support, so the catalyst stability
system for the hydrogenation of
was checked in the case of Au/TiO
2
8
6
4
2
0
0
0
0
0
DNS, and the results were shown in Fig. 4. Obvious decreases in the
DSD yield can be observed (Fig. 4a) at 4 hours reaction for the non-
calcined Au/TiO . While for the catalyst treated at 400 °C for 5 hours,
2
nearly no decreases can be detected for a fourth recycle. On the other
hand, it can be found from Fig. 4b that nearly no changes regarding the
selectivity to DSD were observed for both the non-calcined and 400 °C
treated catalyst.
The selectivity between the nitro and olefinic group was related to
the size of supported Au NPs. It can be found that the average
diameter of Au NPs increased a little (from 4.7 to 4.8 nm) after three
times calcinations (Fig. S3 in the Supporting Information). Therefore,
the selectivity can keep a high level for a fourth recycle. However,
some active sites of the used catalyst might be poisoned by the organic
molecular, and this could lead to the decrease of the yield. The
calcination process at 400 °C can help restore the activity of the
catalysts and regain high yield [10].
Fresh catalyst 1st Re-Use
2nd Re-Use
3rd Re-Use
Au/TiO2
Fig. 4. Stability of the Au/TiO
2
catalyst for the DNS hydrogenation after recycling and
regeneration of the catalyst. While activity needs an appropriate thermal treatment to
recover the original level, no loss of conversion was observed for a fourth recycle (a),
keeping high selectivity values (b).

572
W. Peng et al. / Catalysis Communications 12 (2011) 568–572
[
[
8] X.B. Zhao, H.B. Chen, S.F. Zhang, J. Chem. Ind. Eng. 54 (2003) 1138–1339.
9] A. Corma, H. Garcia, Chem. Soc. Rev. 37 (2008) 2096–2126.
References
[
[
10] A. Corma, P. Serna, Science 313 (2006) 332–334.
11] L. He, L.C. Wang, H. Sun, J. Ni, Y. Cao, H.Y. He, K.N. Ean, Angew. Chem. Int. Ed. 48
[
1] W.C. Peng, X.B. Fan, S.L. Wang, G.L. Zhang, F.B. Zhang, Dyes Pigm. 84 (2010)
218–222.
(2009) 9538–9541.
[
[
[
[
[
2] A. Burawoy, J.P. Critchley, M. Coll, Tetrahedron 5 (1959) 340–351.
[
[
[
[
[
12] A. Saha, B. Ranu, J. Org. Chem. 73 (2008) 6867–6870.
13] R. Zanella, S. Giorgio, C.R. Henry, C. Louis, J. Phys. Chem. B 106 (2002) 7634–7642.
14] G.C. Bond, D.T. Thompson, Catal. Rev. 41 (1999) 319–388.
15] H. Wiener, B. Zaidman, Y. Sasson, Int. J. Hydrogen Energ. 14 (1989) 365–370.
16] K. Shimizu, Y. Miyamoto, T. Kawasaki, T. Tanji, Y. Tai, A. Satsuma, J. Phys. Chem. C
3] J.A. Butera, J.F. Bagli, WO 9109023, 1991.
4] R.F. Kovar, F.E. Arnold, US 3975444, 1976.
5] M. Suchy, P. Winternitz, M. Zeller, WO 9100278, 1991.
6] I.N. Bazanova, N.V. Kholodkova, V.P. Gostikin, Russ. J. Appl. Chem. 75 (2002)
436–440.
113 (2009) 17803–17810.
[
7] W. Gerhard, W. Eckart, P. Bernd, T. Bodo, W. Hans, US 6395934, 2002.