Novel sulfonated carbonaceous materials from p-toluenesulfonic acid/glucose as a high-performance solid-acid catalyst

Article abstract of DOI:10.1016/j.catcom.2010.01.010

A novel carbon-based solid-acid catalyst was simply prepared for the first time by the thermal treatment of p-toluenesulfonic acid (TsOH) with d-glucose at 180 °C in a sealed autoclave and it was proved to have high acidity and to be a highly efficient solid-acid catalyst in the reactions such as esterification of succinic acid with ethanol. Crown Copyright

Full text of DOI:10.1016/j.catcom.2010.01.010

Catalysis Communications 11 (2010) 629–632
Contents lists available at ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Novel sulfonated carbonaceous materials from p-toluenesulfonic acid/glucose
as a high-performance solid-acid catalyst
Baohua Zhang, Jiawen Ren , Xiaohui Liu, Yun Guo, Yanglong Guo, Guanzhong Lu, Yanqin Wang *
*
Laboratory for Advanced Materials, Research Institute of Industrial Catalysis, East China University of Science and Technology, Shanghai 200237, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel carbon-based solid-acid catalyst was simply prepared for the first time by the thermal treatment
Received 11 October 2009
Received in revised form 24 December 2009
Accepted 8 January 2010
of p-toluenesulfonic acid (TsOH) with -glucose at 180 °C in a sealed autoclave and it was proved to have
D
high acidity and to be a highly efficient solid-acid catalyst in the reactions such as esterification of suc-
cinic acid with ethanol.
Available online 14 January 2010
Crown Copyright Ó 2010 Published by Elsevier B.V. All rights reserved.
Keywords:
Carbon based
Solid-acid catalyst
Thermal treatment
Succinic acid esterification
1
. Introduction
The principles of green chemistry and increasing concerns
Herein we report an one-step facile and low-danger method to
synthesize carbon-based solid-acid catalysts by commixing glu-
cose and p-toluenesulfonic acid (TsOH) in a sealed vessel under
thermal treatment of 180 °C. The reaction mechanism is most
probably like this: firstly, the glucose was dehydrated into small
organic molecules, mainly 5-(hydroxymethyl)-2-furaldehyde
(HMF) [22], and the generated HMF could be hydrothermally car-
bonized into a carbon-rich resin as well as react with TsOH to
‘embed’ sulfonic acid groups. The result of the parallel reactions
is that the obtained carbonaceous material was functionalized with
sulfonic groups as shown in Scheme 1. Characterizations showed
about environmental issues have stimulated the research for recy-
clable strong solid acids to replace of conventional toxic and corro-
sive acid catalysts, such as sulfuric acid [1]. Integration of acidic
functional groups (e.g., –SO
3
H) into solid surface, e.g. carbonaceous
[
2–5] or silica-based materials [6–9], has been explored to produce
promising solid acids. Among them, the sulfonated carbon materi-
als have received much attention due to their low costs, high sta-
bility, and high activities.
Sulfonated carbonaceous materials were usually synthesized
through the oxidation of carbon materials by sulfur acid [10–12]
or oleum [13,14] to generate sulfonic acid groups on the surface.
For example, Hara et al. [10,11] obtained a series of carbon-based
that this catalyst exhibited high –SO
3
H loading of ꢀ1.3 mmol/g
and the catalytic performances were also investigated by using
succinic acid esterification as a model reaction. The results showed
that this carbon-based solid acid displayed much better activity
and selectivity than those of sulfonated activated carbon and sulfo-
+
catalysts with acid densities ranging from 0.37 to 1.34 mmol H /
g by the sulfonation of incompletely carbonized sugars. Similarly,
Budarin et al. [12] synthesized a mesoporous sulfonated Starbon-
nated D-glucose.
4
3
00 with 0.5 mmol/g SO H loading. An ordered mesoporous phe-
nol–formaldehyde resin was also functionalized with sulfonate
groups by putting the material in the vapor of fuming sulfuric acid
inside an autoclave [14]. Under optimal conditions, a surface acid
2. Experimental
2.1. Catalyst preparation
+
concentration of 1.3 mmol H /g was achieved on this material.
All of these solid-acid catalysts were synthesized by two steps.
The carbonaceous materials were prepared in first step and then
were sulfonated at harsh oxidation conditions.
The carbohydrate-derived solid-acid catalyst was prepared via
thermal treatment of the mixture of p-toluenesulfonic acid
(TsOH)/glucose at 180 °C. In a typical synthesis, 2 g of D-glucose
and 2 g of TsOH were commixed in a 30 mL Teflon-sealed auto-
clave and maintained at 180 °C for 24 h. The obtained black prod-
ucts were filtered and washed with water and ethanol, and then
oven-dried at 80 °C overnight. This sample was denoted as
*
Corresponding authors. Tel./fax: +86 (21)64253824.
E-mail addresses: cutecube@ecust.edu.cn (J. Ren), wangyanqin@ecust.edu.cn (Y.
Wang).
1
566-7367/$ - see front matter Crown Copyright Ó 2010 Published by Elsevier B.V. All rights reserved.
doi:10.1016/j.catcom.2010.01.010

6
30
B. Zhang et al. / Catalysis Communications 11 (2010) 629–632
OH
O
O
+EtOH
O
Dehydration
HO
OH
HO
HO
O
OH
HO
OH
O
O
OH
H
Monoester(MES)
O
Succinic Acid(SA)
TsOH
O
tOH
E
+
+
O
O
SO H
3
SO H
O
O
O
O
3
SO H
3
O
HO3S
SO H
3
Anhydride(SANH)
Diester(DIES)
Scheme 2. Products obtained in the esterification reaction of succinic acid.
Scheme 1. Possible mechanism for the synthesis of carbon-based solid acid.
ethanol for three times. After dried at 90 °C overnight, this catalyst
was put into a fresh mixture of succinic acid/ethanol again with
keeping same weight ratio of catalyst/succinic acid/ethanol. The
product analysis was same as mentioned above.
Glu-TsOH. As a comparison, 2 g of D-glucose without adding TsOH
was also treated in the similar way and was denoted as Glu-180.
Two reference samples were also prepared by using concen-
trated H
g of -glucose or 1 g of activated carbon and 10 mL of concen-
trated H SO , was sealed into an autoclave and then put into an
2
SO
4
as sulfonate agent. A 30 mL Teflon liner, containing
3. Results and discussion
2
D
3.1. Carbonaceous materials properties
2
4
oven at 180 °C for 24 h. The obtained products were washed with
hot distilled water (>80 °C) and filtered until no sulfate ions were
detected in the filtration water, and dried at 80 °C overnight in
The XRD patterns of samples Glu-TsOH and Glu-180 are shown
in Fig. 1. For sample Glu-180, which was prepared by the thermal
air. The samples were denoted as Glu-SO
3
H and AC-SO
3
H,
treatment of glucose (C
6
H
12
O
6
2
ÁH O was used) at 180 °C in a sealed
respectively.
autoclave, the XRD pattern exhibits 1 weak broad diffraction peak
at 2h angle of 10–30°, which is attributed to (0 0 2) planes of amor-
phous carbon [11]. It is well known that the monodispersed carbon
spheres could be synthesized by the hydrothermal carbonization of
glucose [15] in water, but in our experiments, carbonaceous mate-
rial with carbon element content larger than 74 wt% could be read-
ily obtained without adding any water. The reason probably is that
the carbonization could take place at the aid of water molecules
which generated from the dehydration of glucose in our synthesis.
The XRD pattern of Glu-TsOH displays similar pattern as Glu-180
but with higher intensity, indicating a relative better carbon frame-
work than Glu-180. However, it should be noted that this carbon
framework is still amorphous and far away from graphitization.
The FT-IR spectra of Glu-180 and Glu-TsOH are shown in Fig. 2.
Compared to sample Glu-180, the distinguished features of Glu-
2.2. Characterizations
The powder X-ray diffraction patterns were collected in the h–
h mode using a Bruker D8 Focus diffractometer (Cu K radiation,
2
a
1
k = 1.5406 Å), operating at 40 kV and 40 mA. Nitrogen sorption iso-
therms were measured at 77 K with a Micromeritics ASAP 2020 M
sorption analyzer. Before the measurements, the samples were de-
gassed at 100 °C in vacuum for 12 h. FT-IR was carried out on a
Nicolet Nexus 670 FT-IR spectrometer in the range of 400–
À1
4
000 cm . X-ray photoelectron spectra were measured using a
Thermo ESCA LAB-250 spectrometer with monochromatic Al K
radiation and the XPS results were calibrated using C1s peak at
84.8 eV. Thermal gravimetry analysis (TG) and differential ther-
a
2
malgravimetry (DTA) of the as-synthesized samples were per-
formed at a heating rate of 10 K/min from 40 °C to 700 °C in
flowing N
2
by using a WCT-2 thermal analyzer.
Glu-TsOH
Glu-180
(002)
2
2
0
.3. Catalytic test
.3.1. Succinic acid esterification reaction
In a typical catalytic experiment, 1 mmol succinic acid (SA,
.118 g) and 80 mmol EtOH (4.6 mL) were added to a 25 mL
round-bottom flask with 0.1 g of solid-acid catalyst, and then the
temperature was increased to 80 °C. Few drops of reaction mixture
were withdrawn periodically from the reaction mixture for GC
analysis. Products were analyzed by GC–MS (PerkinElmer Clarus
(101)
5
00) and the products were proved to be monoethyl succinate
(
MES) and diethyl succinate (DIES) (Scheme 2).
2
.3.2. Cycle usage test of Glu-TsOH catalyst
The stability of the catalyst was also tested by following proce-
1
0
20
30
40
50
60
70
80
2θ/degree
dure. After the reaction, the ‘used’ catalyst was separated from the
solution by centrifugation and then washed with a large amount of
Fig. 1. XRD patterns of sample Glu-TsOH and Glu-180.

B. Zhang et al. / Catalysis Communications 11 (2010) 629–632
631
+
ties of the catalysts were 0.5–1.3 mmol H /g depending on the syn-
thesis conditions. But the acid titration experiments demonstrated
much higher acid site densities than the estimations based on sul-
fur elemental analysis. The reason is that abundant phenolic –OH
and –COOH groups were generated in the process of partial oxida-
1
20
Glu-TsOH
Glu-180
-
1
1
1
007 cm-
1
100
032 cm
S=O str.
tion by concentrated sulfonic acid (for sample Glu-SO
SO H) or hydrothermal carbonization of glucose (for sample Glu-
80) [11,18]. The strong sulfonation may also oxidize aliphatic
CH /CH groups to carboxylic acid groups [19], which may further
explain the significant increase in total acid density after sulfona-
tion, just like the Glu-SO H’s acid site is much higher than the
Glu-TsOH’s in Table 1. The XPS analysis further proved most sulfur
3
H and AC-
3
8
0
1
3
2
-1
6
0
OHstr.
-
1
1118cm
SO H str.
1
710 cm
3
C=O bend.
3
element in the catalysts is assigned to SO
ing energy of 168.0 eV [18].
3
H groups with S2p bind-
40
20
3.2. Catalytic activity
3500
3000
2500
2000
1500
1
1000
500
-
Wavenumbers (cm )
Fig. 3 compares the conversions and selectivities to DIES for the
esterification reaction of succinic acid with ethanol catalyzed by
Glu-TsOH, Glu-180, Glu-SO H, and AC-SO H after 1 h, 2 h and
h. No pretreatment except drying the solid catalysts at 80 °C
Fig. 2. FT-IR spectra of sample Glu-TsOH and Glu-180.
3
3
4
Table 1
Surface area and surface acid properties of the different catalysts.
was carried out before the catalysts were added into the reaction
mixtures. Since succinic acid esterification is a kind of autocatalytic
reaction, the conversion and selectivity of blank solution (without
adding any catalyst) under same condition are also shown in Fig. 3.
As shown in Fig. 3, except the non-sulfonated carbonaceous
material Glu-180, AC-SO H shows the lowest conversion of succi-
3
nic acid esterification and also the esterification rate, which will
take more than 4 h to complete the reaction, whereas Glu-TsOH
BET (m2
À1
S content (mmol gÀ1)a
Acid sites (mmol gÀ1)b
Catalysts
S
g
)
Glu-180
Glu-TsOH
<1
<1
<1
506
0
1.02
1.99
3.20
2.66
1.27
1.35
0.56
Glu-SO
AC-SO
3
H
H
3
a
Based on elemental sulfur analysis (EDX).
Acid–base back titration, catalyst reacted with excess 0.05 M NaOH in aqueous
b
3
only need about 1 h. On the other hand, Glu-SO H displayed a sim-
solution at room temperature for 30 min before titration.
ilar conversion and esterification rate in the reaction compared to
Glu-TsOH despite a big difference in total acid density from titra-
3
tion. These results can be well correlated to the loading of SO H
À1
TsOH were the presence of new absorption bands at 1032 cm
,
(Table 1). AC-SO H has the lowest S content (except sample Glu-
3
À1
À1
1
007 cm and 1118 cm , which are attributed to SO
3
H groups
180) while Glu-TsOH and Glu-SO H exhibit similar S content. In
3
[
16,17]. This indicates that the SO H groups were successfully
3
other words, the loading of SO H groups is the key point for the
3
incorporated into the carbon framework by adding TsOH in the
synthesis system. On the other hand, the bands due to –OH stretch-
activities of the catalysts.
Despite similar activities between Glu-TsOH and Glu-SO H, the
selectivity to DIES for the Glu-TsOH catalyst was found to be about
3
À1
À1
ing at 3420 cm , C@O stretching at 1710 cm , and C@C bonds
À1
stretching at 1620 cm were observed for both samples indepen-
two times greater than that of Glu-SO H catalyst screened in the
3
dent of the sulfonation.
esterification within 1 h. This may be ascribed to the different sur-
The acid site densities of the catalysts were determined by
acid–base back titration and the sulfur contents were measured
by energy dispersive X-ray analysis (EDX). These results are listed
face properties with different synthesis conditions. According to
some reports [12,20], a hydrophobic surface has been proved to
be favorable in esterification reactions. This is because the water
would contribute not only to a reverse hydrolysis [21] but also to
a competitive protonation involving the water and the alcohol.
Obviously, hydrophilic surface is not conducive to the esterification
in Table 1. It is obvious that samples Glu-TsOH and Glu-SO
3
H
exhibited higher sulfur content than AC-SO H. If all sulfur element
3
in the catalysts was assumed as –SO
3
H groups, the acid site densi-
Conversion (%)
Selectivity to DIES(%)
100
100
9
0
90
80
70
60
50
40
30
20
10
0
80
70
60
50
40
30
20
10
0
1h
2h
4h
1h
2h
4h
Glu-TsOH
Glu-SO
3
H
AC-SO
3
H
Glu-180
No Catalyst
Fig. 3. The conversions and selectivities to DIES of the catalysts and blank solution (without catalyst) at different reaction time.

6
32
B. Zhang et al. / Catalysis Communications 11 (2010) 629–632
Table 2
The conversions and selectivities to DIES of Glu-TsOH in cycle usage test.
tion safer by avoiding usage of dangerous chemicals. The so-
prepared catalyst exhibits much higher catalytic activity than sul-
fonated active carbon in the reaction of esterification of succinic
acid with ethanol. The cycle usage test indicated that the catalyst
prepared by this method was relative stable. It would be noted that
the method described here can be further extended to one-step
synthesis of various functionalized carbon materials from saccha-
ride and aromatic compounds with target functional groups, such
as glucose/salicylic acid system.
Round
4 h
10 h
Conversion (%)
Selectivity (%)
Conversion (%)
Selectivity (%)
1
2
3
4
5
6
>99
>99
>99
97
97
95
>99
67
43
36
32
33
>99
>99
99
99
99
96
79
73
74
73
Acknowledgements
due to the absorption of water molecules generated in the reaction.
To estimate the surface hydrophobicity of our catalysts, TG-DTA
analysis was conducted and the mass loss below than 150 °C in
TG curves, which is due to the loss of absorbed water, was consid-
ered to indicate the hydrophobic property. The TG curves of the
This project was supported financially by the 973 Program of
China (2010CB732306), the National Natural Science Foundation
of China (Nos. 20673037 and 20973058), the Commission of Sci-
ence and Technology of Shanghai Municipality (08JC1407900)
and East China University of Science and Technology, China.
catalysts (not shown) showed that Glu-SO
water) was more hydrophilic than Glu-TsOH (8 wt%) while AC-
SO H is the most hydrophilic sample (13.5 wt%). This result was
well agreeable to their catalytic performances, is that Glu-TsOH
displayed higher selectivity compared to Glu-SO H and AC-SO H.
3
H (containing 11 wt%
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