A novel highly ordered mesoporous carbon-based solid acid for synthesis of bisphenol-A

Article abstract of DOI:10.1039/c5ra24966j

A novel highly ordered mesoporous carbon-based solid acid was prepared through controlled sulfonation of F127 type mesoporous carbons prepared via a solvent evaporation induced self-assembly method. The influence of sulfonation temperature was investigated, suggesting an optimum temperature of 180 °C. The sulfonated samples were characterized by means of N₂ adsorption-desorption, XRD, TEM and FT-IR. The SO₃H group-functionalized mesoporous carbon showed a specific surface of 393 m² g^-1, pore volumes of 0.33 cm³ g^-1, an average pore size of 3.7 nm and a SO₃H group density of 1.71 mmol g^-1. The mesoporous carbon-based solid acid effectively catalyzed the condensation of phenol with acetone. The increased catalytic performance was attributed to a uniform mesoporous structure and hydrophobic surface properties.

Full text of DOI:10.1039/c5ra24966j

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A Novel Highly Ordered Mesoporous Carbon-based Solid Acid
for Synthesis of Bisphenol-A
Xiuqin Dong a, b, Yuan Jiang a, b, Wenbin Shan a, b, and Minhua Zhang a, b,
*
a Key Laboratory for Green Chemical Technology of Ministry of Education,
R&D Center for Petrochemical Technology, Tianjin University
Tianjin 300072, P R China
b Collaborative Innovation Center of Chemical Science and Engineering
Tianjin300072, China
* Corresponding author. Tel.: +86ꢀ22ꢀ27406119; fax: +86ꢀ22ꢀ27406119.
Eꢀmail address: mhzhang@tju.edu.cn (Minhua Zhang)

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Abstract
A novel highly ordered mesoporous carbonꢀbased solid acid was prepared through
controlled sulfonation of F127 type mesoporous carbons prepared via a solvent
evaporation induced selfꢀassembly method. The influence of sulfonation temperature
was investigated, suggesting an optimum temperature of 180℃. The sulfonated
samples were characterized by means of N2 adsorption–desorption, XRD, TEM and
FTꢀIR. The SO3H groupꢀfunctionalized mesoporous carbon showed a specific surface
of 393 m2/g, pore volumes of 0.33 cm3/g, an average pore size of 3.7 nm and a SO3H
group density of 1.71mmol/g. The mesoporous carbonꢀbased solid acid catalyzed
effectively the condensation of phenol with acetone. The increased catalytic
performance was attributed to uniform mesoporous structure and hydrophobic surface
properties.
Keywords: Mesoporous carbon-based solid acid; Self-assembly method; Sulfonation
temperature; Bisphenol-A

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1. Introduction
BisphenolꢀA (BPA) is an important raw material for the production of many
polymers in organic chemical industry, such as epoxy resins and polycarbonates.1
Traditionally, it is produced by acidꢀcatalyzed condensation reaction of acetone and
phenol. Because of equipment corrosion, environment pollution and separation
difficulty, homogeneous acid catalysts (e.g. H2SO4, HCl) have been eliminated. In
order to solve these problems, the use of heterogeneous catalysts has been explored.
Solid acids, which can be readily separated from the products, avoid the corrosion and
pollution problems, thereby leading to lower production costs. Until now, a number of
new kinds of catalysts have been developed, ranging from heteropoly acids,2 mixed
oxides,3 zeolites,4 acidꢀfunctionalized mesoporous silicas,5, 6 ionic liquid,7 silylated
derivatives,8 etc. Most of these solid catalysts could be found only in the patent and
literature, far from industrialized application. In industry, ionꢀexchange resins are
most widely used for the synthesis of bisphenolꢀA due to their high catalytic
performance, easy separation and less corrosion problems. It was reported that
thiolꢀmodified ionꢀexchange resins, such as Amberlyst, exhibit very good catalytic
activity with around 90% selectivity.9 However, several drawbacks of the
ionꢀexchange resins may directly reduce the catalyst lifespan, which increases the
production costs to a certain extent. The disadvantages can be summed up in three
aspects: (i) Cannot be used at higher reaction temperatures because of the poor
thermal stability. (ii) Easily poisoned by the reaction medium, side product water. (iii)
Swelling and rupture of the resins are inevitable. Thus, efforts should be made to

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develop thermally stable, hydrophobic catalysts with longer lifespan for bisphenolꢀA
synthesis.
Recently, much attention has been focused on carbonꢀbased solid acid catalysts
due to their chemical inertness, thermal stability and excellent catalytic activity.10, 11
Michikazu Hara et al.12ꢀ16 first reported a series of carbonꢀbased solid acid catalysts,
which can be readily prepared by incomplete carbonization and sulfonation of
polycyclic aromatic hydrocarbons or carbohydrates such as sugar, starch and cellulose,
etc. Despite the small specific surface area (ca. 2m2/g), the carbon material with
sufficient amount of sulfonic acid groups showed excellent catalytic performance for
liquid phase acidꢀcatalyzed reactions. Wu and coꢀworkers17 also reported a
vapourꢀphase transfer method to prepare sulfonic acid groupꢀfunctionalized
mesoporous carbon. It catalyzed efficiently the liquidꢀphase Beckmann rearrangement
of cyclohexanone oxime and condensation reactions involving bulky aromatic
aldehydes. Moreover, grapheneꢀbased catalysis has also been prepared as an efficient
solid catalyst.18, 19 Catalytic tests demonstrated the sulfated graphene was a good
catalyst with high activity for the acid catalyzed liquid reactions such as the
esterification of acetic acid. However, as for hydrophobic acidꢀcatalyzed reactions, the
hydrophilic functional groups inside the carbon restrict the incorporation of
hydrophobic reactants into the active sites.20 As a result, the carbon material exhibits
poor or no catalytic activity.
Sulfonated ordered mesoporous materials as a promising replacement for
sulfonic acids have been developed due to its defined pore structures, high specific

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surface area.17, 21ꢀ23 The ordered mesoporous structure provides more active sites for
the reaction of large molecules.24 Feng and coꢀworkers25 reported a method to prepare
the sulfonated ordered mesoporous carbon and applied it to catalyze the formation of
bisphenolꢀA. In this method, sulfonic acidꢀcontaining aryl radicals was grafted on the
carbon surface by covalent attachment. The catalyst showed a phenol conversion of
8.9% (28.6% maximum) with high selectivity of 84.0% to p,p′ꢀbisphenolꢀA. However,
this method is time consuming and sacrifice the silica template. Wan26 showed that a
highꢀcontent sulfonic acid group functionalized ordered mesoporous polymerꢀbased
solid acid, prepared by a simple surfactant templating approach and oxidation
treatment, was very selective and stable for bisphenolꢀA synthesis. The stability is
attributed to the hydrophobic nature of the mesoporous polymerꢀbased solids.
In this paper, we reported a novel highly ordered mesoporous carbonꢀbased solid
acid with high SO3H density and specific surface area prepared through controlled
sulfonation of F127 type mesoporous carbons prepared via a solvent evaporation
induced selfꢀassembly method. Then the catalysts were examined as solid acid
catalysts in bisphenolꢀA synthesis. Its catalytic performance was also compared with
other commercial acid catalysts.
2. Experiment Section
2.1 Catalysts preparation
The systhesis method of FDUꢀtype mesoporous carbon was reported
previously.27 In typical preparation procedure, 0.61g phenol (6.50mmol) was melted
at 40ꢀ42℃ followed by the addition of 0.13g 20 wt% NaOH (0.65mmol) with

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magnetic stirring for 10min. 1.05g formalin (13.0mmol, 37 wt%) aqueous solution
was added dropꢀwise, and the mixture was stirred at 70℃ for 1h. Then, the reaction
mixture was cooled to room temperature and the pH was adjusted to neutral by adding
appropriate quantities of 2M HCl under stirring. Water was removed under vaccum
below 50℃. The mixture obtained was dissolved in ethanol. The ethanol solution of
the above precursors was added to a second solution containing 1.00g of Triblock
copolymer (PEOꢀPPOꢀPEO, pluronic 127, SigmaꢀAldrich) and 20.0g of ethanol. The
mixture was stirred to form a homogeneous solution with the molar ratio of F127:
Phenol: Formaldehyde: Ethanol = 0.012:1:2:67. The solution was then transferred to a
culture dish and ethanol was evaporated at room temperature over 5ꢀ8h to form a
transparent membrane. The membrane was heated in an oven at 100℃ for 24h to
obtain the phenolic resins/F127 composites. The composites were calcined at 350℃
under nitrogen for 5h with a temperature increase rate of 1℃/min to remove the
template F127. Further carbonization was carried out at 500℃ for 3h at a rate of 2℃
/min under nitrogen atmosphere. The sample obtained, FDUꢀ15ꢀ500 (500 denotes the
carbonization temperature), was sulfonated in concentrated H2SO4 (98 wt%) at
140ꢀ200 ℃ for 10h in a Teflonꢀlined autoclave. The sulfonated sample,
FDUꢀ15ꢀ500ꢀTS (Ts denotes the sulfonation temperature), was then washed with hot
deionized water to remove the physically adsorbed H2SO4 until the pH of filtrate
became neutral and finally dried at 60℃ for 8h under vacuum.
2.2 Catalysts characterization
The Xꢀray diffraction (XRD) patterns were collected on a Rigaku D/Max 2500

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type Xꢀray powder diffractometer with Cu Kα radiation at 40kV and 30mA. Nitrogen
adsorptionꢀdesorption isotherms were recorded at 77K on a Micromeritics Tristar
3000 instrument. All samples were degassed at 423K under vacuum for at least 12h
prior to measurements. The Brunauer–Emmett–Teller (BET) method was applied to
calculate the specific surface area. The total pore volume was estimated from the
amount of N2 adsorbed at P/P0= 0.98. The mesoporous volume, pore size distribution
and pore diameter were determined from the desorption branch of the isotherm using
the Barrett–Joyner–Halenda (BJH) method. Transmission electron microscopy (TEM)
images were obtained on FEI Tecnai G2 F20 microscope. FTꢀIR spectra were
recorded on a Thermo Scientific Nicolet 560 FTIR spectrometer with 64 scans at 4
cm−1 resolution. The amount of SO3H group was quantified by an acidꢀbase titration
method, which involves an aqueous ionꢀexchange step of H+ ions (SO3H group) of the
catalyst with NaCl, followed by titration of the resulting filtrate with NaOH.28 The
total acid density was estimated by backꢀtitration of excessive NaOH with HCl.
2.3 Catalytic activity measurement for the synthesis of bisphenol-A
All catalysts were tested in condensation of phenol with acetone under
atmospheric pressure in a 50 mL glass reactor equipped with a reflux condenser and a
magnetic stirrer. In a typical experiment, 0.58g of acetone and 9.40g of excess phenol
was mixed under vigorous stirring in the presence of the mesoporous carbonꢀbased
solid acid catalyst (0.30 g). The reaction mixture was kept at 358K in a water bath for
8h. Samples were withdrawn from the reaction mixture at 2h intervals and then
separated using filtering syringe. The resulting solution was analyzed by a high

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performance liquid chromatograph (HPLC, Agilent 1100) equipped with a column of
Zorbox C18, 0.5ꢁm, 250 ×0.46mm. The mobile phase was a mixture of
methanolꢀwater (63: 37, V/V) and the flow rate was 0.5ml/min. The amount of
bisphenolꢀA was determined by external standard method. Conversion and selectivity
were calculated based on converted acetone.
3. Characterization of the catalyst
Carbonation temperature and different sulfonation procedures are extremely
important, which have a great impact on the porous structure and the content of SO3H
group.17, 23, 27, 28 In our previous studies,29 the effect of carbonization temperature was
investigated. The optimal carbonization temperature was 500℃ and the mesoporous
carbonꢀbased solid acid catalyst carbonized under 500℃ contained highly ordered
mesoporous channel structure. Here, the influence of sulfonation temperature on
porous structure, strong acid density and catalytic performance were systematically
investigated.
FDUꢀ15ꢀ500
100
FDUꢀ15ꢀ500ꢀ140
FDUꢀ15ꢀ500ꢀ160
FDUꢀ15ꢀ500ꢀ180
FDUꢀ15ꢀ500ꢀ200
110
200
x10
1
2
3
2θ/degree
4
5
Fig. 1: Smallꢀangle XRD patterns of mesoporous carbonꢀbased solid acid catalysts

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under different sulfonation temperatures
Fig.1 shows the XRD patterns of FDUꢀ15ꢀ500 and corresponding mesoporous
carbon obtained after the sulfonation was performed at various temperatures
(140ꢀ200℃). FDUꢀ15ꢀ500 clearly showed an intense diffraction peak together with
two weak peaks which can be indexed as the 100, 110 and 200 planes of 2D
hexagonal structure (p6mm) (Fig. 1), indicating a wellꢀordered structuring of the
mesopores. The peak intensity of the 100 reflection decreased after sulfonation,
indicating that the sulfonation treatment may partially destroy the mesostructure order
of the material (see later from the BET surface areas in Table 1). However, the
samples sulfonated at lower temperatures ranging between 140ꢀ180 ℃ still
maintained the ordered mesostructure. By increasing the sulfonation temperature to
200℃, the peak of 100 plane almost disappeared presumably as a result of framework
collapse. It demonstrates that soft sulfonation is important to keep the mesoporous
organization of the carbon material.
FDUꢀ15ꢀ500
FDUꢀ15ꢀ500
(a)
(b)
FDUꢀ15ꢀ500ꢀ140
FDUꢀ15ꢀ500ꢀ160
FDUꢀ15ꢀ500ꢀ180
FDUꢀ15ꢀ500ꢀ200
0.4
0.3
0.2
0.1
0.0
400
300
200
100
0
FDUꢀ15ꢀ500ꢀ140
FDUꢀ15ꢀ500ꢀ160
FDUꢀ15ꢀ500ꢀ180
0.0
0.2
0.4
0.6
0.8
1.0
2
4
6
8
Relative Pressure(P/P0)
Pore Diameter (nm)
Fig. 2: N2 adsorptionꢀdesorption isotherms (a) and BJH pore distribution (b) of
mesoporous carbonꢀbased solid acid catalysts under different sulfonation temperatures
Fig. 2 shows the N2 adsorptionꢀdesorption isotherms and pore size distribution

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curves for FDUꢀ15ꢀ500 and the corresponding sulfonated mesoporous carbon at
various temperatures. FDUꢀ15ꢀ500 and the samples sulfonated between 140ꢀ180℃
had typical typeꢀ Ⅳ N2 adsorption isotherms with a well defined capillary
condensation step at P/P0≈0.4 and the H1ꢀtype hysteresis loops in the relative
pressure range of 0.45ꢀ0.7, and also showed narrow BJH pore size distribution. These
indicated that the samples were characteristic of mesoporous carbon with cylindrical
channels.
Table 1: Pore structure parameters of mesoporous carbonꢀbased solid acid catalysts
under different sulfonation temperatures
Sample
Total surface
Pore
volume(cm3/g)
0.59
Average pore a0(nm)
diameter (nm)
area (m2/g)
FDUꢀ15ꢀ500
655
4.0
3.6
3.7
3.7
—
12.1
11.9
11.9
11.8
11.5
FDUꢀ15ꢀ500ꢀ140
FDUꢀ15ꢀ500ꢀ160
FDUꢀ15ꢀ500ꢀ180
FDUꢀ15ꢀ500ꢀ200
386
0.30
338
0.23
393
0.33
25
0.02
Table 1 summarizes the textural parameters of mesoporous carbon before and
after sulfonation. An obvious decrease for the sulfonated mesoporous carbon in
specific surface area, pore volume and pore size should be due to the structural shrink
or partial framework collapse.17 FDUꢀ15ꢀ500ꢀ180 showed the highest BET surface
area and the pore volume after sulfonation. The values were 393 m2/g and 0.33 cm3/g
respectively. When sulfonation temperature increased to 200℃, the mesoporous
carbon material totally lost its mesostructure under such hard sulfonation treatment.
TEM images, presented in Fig. 3, prove that FDUꢀ15ꢀ500 has ordered mesoporous

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morphology. After sulfonation, FDUꢀ50ꢀ500ꢀ180 retains ordered mesoporous
structure. The pore size is about 3.7 nm, well consistent with the result calculated by
N2 adsorption–desorption experiment (Table 1). In addition, the size of the
carbonꢀfilled channels is about 12.3 nm. The presence of elemental sulfur is clearly
revealed by the EDX pattern (Fig. 4) and the content is estimated to be 1.74mmol/g
from elemental analysis. The value is close to the result obtained from the acidꢀbase
titration method, which is 1.71mmol/g (Fig. 6).
Fig. 3: TEM images of FDUꢀ15ꢀ500 (a) and FDUꢀ15ꢀ500ꢀ180 (b)
Fig. 4: EDX spectra of FDUꢀ15ꢀ500ꢀ180 catalyst
The FTꢀIR spectra for FDUꢀ15ꢀ500 and sulfonated samples are shown in Fig. 5.

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The vibration bands at 1032 cmꢀ1 was assigned to symmetric stretching of S=O bond
caused by the introduction of SO3H groups into the mesoporous carbon.17, 30 The
presence of absorption at 1220 cmꢀ1 was due to Ar–OH stretching.30 The bands at
1463 cmꢀ1, 1602 cmꢀ1 was due to C=C stretching mode remained after sulfonation.17
The band at 1711 cmꢀ1 was typical of the C=O stretching mode of the ꢀCOOH and
ꢀCOOꢀ groups. The broad band at 3426 cmꢀ1 was assigned to the O–H stretching
modes of the ꢀCOOH and phenolic OH groups.22
C=C
OH
1463cmꢀ1
S=O
1220cmꢀ1
3426cmꢀ1
1032cmꢀ1
C=O
1711cmꢀ1
1602cmꢀ1
FDUꢀ15ꢀ500ꢀ200
FDUꢀ15ꢀ500ꢀ180
FDUꢀ15ꢀ500ꢀ160
FDUꢀ15ꢀ500ꢀ140
FDUꢀ15ꢀ500
4000
3500
3000
2500
2000
1500
1000
500
Wavenumber(cmꢀ1)
Fig. 5: FTꢀIR spectra of mesoporous carbonꢀbased solid acid catalysts under different
sulfonation temperatures
ꢀSO3H Density
3.2
Total Acid Density
2.8
2.4
2.0
1.6
1.2
140
160
180
200
Sulfonation Temperature/
℃
Fig. 6: Acid density of mesoporous carbonꢀbased solid acid catalysts under different
sulfonation temperatures

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Fig. 6 showed the acid loadings obtained by acidꢀbase titration method. The
amounts of SO3H and total acid increased with increasing sulfonation temperature,
indicating that relatively high sulfonation temperature should be necessary. With
respect to FDUꢀ15ꢀ500ꢀ200, the values of SO3H density and total acid density were
1.93 and 3.24 mmol/g respectively.
4. Catalytic activity
The catalytic performance of FDUꢀ15ꢀ500ꢀSO3H was investigated by
condensation of phenol with acetone (Fig. 7). Acetone conversation increases with
reaction time. FDUꢀ15ꢀ500ꢀ180 clearly shows higher catalytic activity, reaching 42.7%
conversation of acetone after 10h of reaction. BisphenolꢀA selectivity also increases
slightly with reaction time. The maximum selectivity 68% was achieved at 8 h. It is
worth noting that the selectivity decreases when the conversion goes on. The
selectivity to bisphenolꢀA decreases after 8h probably due to accumulation of
byproducts or loss of active sites.
75
70
65
60
55
50
40
30
20
10
0
FDUꢀ15ꢀ500ꢀ140
FDUꢀ15ꢀ500ꢀ160
FDUꢀ15ꢀ500ꢀ180
FDUꢀ15ꢀ500ꢀ200
FDUꢀ15ꢀ500ꢀ140
FDUꢀ15ꢀ500ꢀ160
FDUꢀ15ꢀ500ꢀ180
FDUꢀ15ꢀ500ꢀ200
(a)
(b)
2
4
6
8
10
0
2
4
6
8
10
Reaction Time/h
Reaction Time/h
Fig. 7: Effect of sulfonation temperature on catalytic performance of mesoporous
carbonꢀbased solid acids

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Conditions: 0.30 g catalyst; 358 K; 0.58 g acetone and 9.4 g phenol.
Among the mesoporous carbon obtained after the sulfonation was performed
between 140ꢀ180 , FDUꢀ15ꢀ500ꢀ180 exhibits the best catalytic performance due to
℃
the highest amount of SO3H (Fig. 8). Nevertheless, the largest amount of active sites
may not be the only reason for the best catalytic performance. With respect to
FDUꢀ15ꢀ500ꢀ200 with much low specific surface area (25m2/g), a lower conversation
was observed. In summary, FDUꢀ15ꢀ500ꢀ180 shows the highest catalytic activity
probably owing to the ordered mesoporous structure, high specific surface (393m2/g)
and large acid amount (SO3H group, 1.71mmol/g).
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
900
800
700
600
500
400
300
200
100
0
40
35
30
25
20
140
160
180
200
Sulfonation Temperature/
℃
Fig. 8: Effect of BET specific surface area and surface acid density on catalytic
performance
Conditions: 0.30 g catalyst; 358 K; 8 h; 0.58 g acetone and 9.4 g phenol.
In order to evaluate the catalytic activity of FDUꢀ15ꢀ500ꢀ180 in this reaction, a
comparative study was made with three solid acid catalysts (Commercial strongly
acidic cation exchange resin 001
×7, D072 and amorphous carbonꢀbased solid acid).
Fig. 9 shows time profiles of acetone conversion and bisphenolꢀA selectivity on these

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catalysts. With respect to 001×7 and amorphous carbon, the reaction gradually
reached equilibrium after 8h reaction and selectivity to BisphenolꢀA is lower than
45%. Among these catalysts, FDUꢀ15ꢀ500ꢀ180 shows the highest activity.
(a)
FDUꢀ15ꢀ500ꢀ180
001×7
D072
FDUꢀ15ꢀ500ꢀ180
001
D072
Amorphous Carbon
(b)
50
40
30
20
10
0
80
70
60
50
40
30
×
7
Amorphous Carbon
2
4
6
8
10
0
2
4
6
8
10
Reaction Time/h
Reaction Time/h
Fig. 9: Effect of different catalysts on phenolꢀacetone condensation reaction
Conditions: 0.30 g catalyst; 358 K; 0.58 g acetone and 9.4 g phenol.
Although the acid amount of 001
larger than FDUꢀ15ꢀ500ꢀ180 (Fig. 10), FDUꢀ15ꢀ500ꢀ180 shows the best catalytic
performance with 39.4% conversation. As for 001 7, SO3H group loading is 2.41
×7, D072 and amorphous carbon is obviously
×
mmol/g, but it shows much less activity. This result may be related to the small pores
which partially block access to the active surface sites. D072 with large pores and
high density of SO3H group still exhibits less activity than FDUꢀ15ꢀ500ꢀ180, which is
probably attributed to the weak hydrophilic property of the material. For this reason,
byproduct water may poison the active sites. With respect to amorphous carbon,
extremely low surface area (<2m2/g) and nonporous structure are responsible for the
low activity. In summary, the enhancement of catalytic performance of the
FDUꢀ15ꢀ500ꢀ180 is due to its ordered mesoporous structure and hydrophobic

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substrate of carbonꢀbased catalyst, which ensure good accessibility to active sites.
45
40
35
30
25
20
15
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
FDUꢀ15ꢀ500ꢀ180 001
×
7
D072 Amorphous Carbon
Catalysts
Fig. 10: Effect of surface acid density on catalytic performance
Conditions: 0.30 g catalyst; 358 K; 8 h ; 0.58 g acetone and 9.4 g phenol.
90
80
70
60
50
40
30
90
85
80
75
70
65
60
55
90
80
70
60
50
40
30
20
10
0
(a)
(b)
ꢀSH+Cat
ꢀSH
10
0.00 0.03 0.06 0.09 0.12 0.15 0.18
Amount of mercapto acetic acid/g
2
4
6
8
Reaction Time/h
Fig. 11: Effect of mercaptoacetic acid on phenolꢀacetone condensation reaction
a Conditions: 0.30 g catalyst; 358 K; 8 h; 0.58 g acetone and 9.4 g phenol.
b Conditions: 0.30 g catalyst; 0.12 g mercapto acetic acid ; 358 K; 0.58 g acetone
and 9.4 g phenol.
For the further improvement of the catalyst of condensation of phenol with
acetone, mercapto acetic acid as promoters was introduced. Both of acetone
conversation and bisphenolꢀA selectivity increase significantly with increasing
mercapto acetic acid, until 0.06g (Fig. 11a). 75.2% conversation and 85.0% selectivity
was observed at the addition of 0.12g. However, mercapto acetic acid exhibits no
catalytic activity without the catalyst (Fig. 11b), demonstrating that ordered

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mesoporous carbonꢀbased solid acid involves active sites required for the formation of
bisphenolꢀA.
The proposed mechanism for bisphenolꢀA formation is similar to that reported in
Refs. [6] and [31] as shown in Scheme 1. The mercapto group is supposed to form
carbocation intermediates through nucleophilic attack on the protonated acetone. The
positive charged sulfur intermediates may be more stable than the protonated
acetone,32 leading to increases in reaction rate. Then, bisphenolꢀA is formed by
nucleophilic attack of the positive charged sulfur intermediates by the second phenol.
Selectivity to
p,p′ꢀbisphenolꢀA significantly increases owing to enhanced steric
hindrance of the positive charged sulfur intermediates.
OH
OH
+
+OH
HOH
O
+
HO3SꢀR
RꢀSH
ꢀH2O
+
+
SR
SR
SHꢀR
SR
OH
RꢀSH
+
ꢀH+
OH
OH
Scheme 1: Possible mechanism in the condensation reaction of phenol and acetone
5. Conclusion
A novel highly ordered carbonꢀbased solid acid catalyst has been prepared
through controlled sulfonation of FDUꢀ15ꢀ500 mesoporous carbons prepared by
softꢀtemplate method. The final bisphenolꢀA selectivity was 68%, which was more
excellent than the commercial strongly acidic cation exchange resin 001
×7, D072
and amorphous carbonꢀbased solid acid. The uniform mesoporous structure and
hydrophobic property make it a highly active catalyst for the synthesis of
BisphenolꢀA.

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Acknowledgments
This work was financially supported by National Natural Science Foundation of
China (Grants No. 21104035).

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386x216mm (72 x 72 DPI)