Table 1 Surface areas and amounts of acid sites of the TESPT-
x-MCM and MPTES-x-MCM catalysts
Table 2 Acetylation of anisole with acetic anhydride over TESPT-
x-MCM and MPTES-x-MCM catalysts at 90 uC for 1 h
Catalyst TESPT-x-MCM
Catalyst MPTES-x-MCM
Catalyst TESPT-x-MCM
Conversion (%) Yield (%)
Catalyst MPTES-x-MCM
Conversion (%) Yield (%)
x
Surface
area/m g
Amount of acid
sites/mmol g
x
Surface
area/m g
Amount of acid
sites/mmol g
x
x
2
21
21
2
21
21
1
0
62
62
71
98
81
73
66
10 31
20 50
30 52
50 68
31
49
51
65
1
2
3
5
6
8
0
970
960
740
420
213
24
2.64
3.08
3.32
5.63
1.52
1.50
10 905
20 860
30 749
50 347
0.80
1.45
1.61
2.01
20 71
30 98
50 88
60 75
80 67
0
0
0
0
0
A large amount of sulfonic acid groups with strong strength is
essential to obtain high conversion and yield in the acetylation of
anisole. The TESPT-x-MCM catalysts prepared using TESPT
showed large surface areas and large amounts of acid sites
compared to the corresponding MPTES-x-MCM catalysts.
Although MPTES is a well-known material used for the
introduction of sulfonic acid groups into mesoporous materials,
TESPT, having tetrasulfide linkages, was more effective than
MPTES, without inducing a significant loss in the regularity of the
mesopores. The acid strength of the sulfonic acid groups in the
TESPT-30-MCM catalyst was suitable to achieve an exceptional
yield of the acetylation product. The 97.5% yield of the acetylated
product obtained from anisole on the TESPT-30-MCM catalyst
has not previously been reported even in the case of Nafion-
when the mesoporous materials prepared from the mixture of large
amounts of TESPT or MPTES showed high regularity in the
mesopores.
The amounts of active acid sites on the sulfonic acid-
incorporated-MCM were determined from the decrease in pH of
their aqueous slurries caused by the addition NaCl solution. The
exchange of protons of the sulfonic acid groups with sodium ions
was responsible for the decrease in pH. Table 1 lists the surface
areas and amounts of acid sites in the sulfonic acid-incorporated-
MCM catalysts. Increasing the amount of TESPT in the synthetic
mixtures decreased the surface area of TESPT-x-MCM catalysts,
while increasing the amounts of acid sites up to the TESPT-50-
MCM catalyst. The same trends were also observed in MPTES-
x-MCM catalysts, but their amounts of acid sites were
considerably lower than those of TESPT-x-MCM catalysts.
The acetylation of anisole with acetic anhydride (eqn (1)) is a
typical acid-catalyzed reaction. Various homogeneous and hetero-
geneous acids were reported to be active for the acetylation, but
their activities and selectivities vary remarkably according to the
5
15
16
incorporated solid acid, sulfated zirconia, and zeolite H-Beta.
Notes and references
1
2
V. Dufoud and M. E. Davis, J. Am. Chem. Soc., 2003, 125, 9403–9413.
S. Che, A. E. Garcia-Bennett, X. Liu, R. P. Hodgkins, P. A. Wright,
D. Zhao, O. Terasaki and T. Tasumi, Angew. Chem., Int. Ed., 2003, 42,
5,10,11
catalysts employed.
3930–3934.
Homogeneous acid catalysts such as
3
4
V. S.-Y. Lin, C.-Y. Lai, J. Huang, S.-A. Song and S. Xu, J. Am. Chem.
Soc., 2001, 123, 11510–11511.
Q. Yang, M. P. Kapoor, N. Shirokura, M. Ohashi, S. Inagaki,
J. N. Kondo and K. Domen, J. Mater. Chem., 2005, 15, 666–673.
AlCl and FeCl showed a high yield of the acetylated product of
3
3
more than 90%. However, the generation of harmful chlorine gas
and a large amount of waste water lower the feasibility of these
1
2
5 M. Alvaro, A. Corma, D. Das, V. Fornes and H. Garcia, J. Catal.,
005, 231, 48–55.
catalysts for commercial applications. The incorporation of
,2,2-trifluoro-1-trifluoromethylethane sulfonic acid (Nafion) into
2
1
6
Y.-F. Feng, X.-Y. Yang, Y. Di, Y.-C. Du, Y.-L. Zjang and F.-S. Xiao,
J. Phys. Chem. B, 2006, 110, 14142–14147.
mesoporous materials introduced extremely strong acid sites on
them. Too strong acid sites, however, accelerated the formation of
adducts between the ketone and anisole molecules, and thus, the
7
8
H. T. Clarke, Org. Synth., 1940, 20, 23, (Org. Synth. Coll., 1955, 3, 226).
T. Asefa, M. J. MacLachlan, N. Coombs and G. A. Ozin, Nature, 1999,
402, 867–871.
5
yield of the acetylated product did not exceed 65%.
9 Each self-supported wafer of the catalyst was made of 10 mg. The wafer
was evacuated at 200 uC for 2 h prior to exposing it to ammonia of
50 Torr at 50 uC. The desorption of ammonia was started after
ð1Þ
removing gaseous and physically adsorbed ammonia by evacuation.
0 S. Shylesh, S. Sharma, S. P. Mirajkar and A. P. Singh, J. Mol. Catal. A:
Chem., 2004, 212, 219–228.
1
The performance of TESPT-x-MCM and MPTES-x-MCM as
catalysts in the acetylation of anisole was strongly dependent on
the type of silane used for the incorporation of sulfonic acid
groups, as shown in Table 2. The conversion on the TESPT-30-
MCM catalyst, which was defined as the percentage of anisole
1
1 M. Eissen and J. O. Metzger, Chem.–Eur. J., 2002, 8, 3581–3585.
12 B. S. Furniss and A. I. Vogel, Vogel’s Textbook of Practical Organic
Chemistry: Including Qualitative Organic Analysis, Longman, London,
4th edn, 1978, p. 776.
1
3 The p-methoxyacetophenone was prepared by acetylation of 10 mmol of
anisole with 11 mmol of acetic anhydride over 0.2 g of catalyst at 90 uC
for 1 h in 30 ml three-neck round-bottomed flask.
13,14
consumed, was as high as 98%.
The yield of the acetylated
14 Anisole, o- and p-methoxyacetophenone in the products were analysed
using a high performance liquid chromatograph (Agilent 1100 series):
product was also the highest (97.5%) over the TESPT-30-MCM
catalyst, due to its exceptional selectivity for the acetylation.
MPTES-x-MCM catalysts showed similar variations in the
conversion and yield with the amount of MPTES added, but the
conversions and yields were considerably lower than those
obtained using the corresponding TESPT-x-MCM catalysts.
1
Waters Symmetry column (150 mm 6 4.6 mm), mobile phase
(acetonitrile : water = 7 : 3), detection wavelength = 230 nm.
5 J. Deutsch, A. Trunschke, D. Muller, V. Quaschning, E. Kemnitz and
1
H. Lieske, J. Mol. Catal. A: Chem., 2004, 207, 51–57.
6 E. G. Derouane, C. J. Dillon, D. Bethell and S. B. Derouane-abd
Hamid, J. Catal., 1999, 187, 209–218.
1
This journal is ß The Royal Society of Chemistry 2007
Chem. Commun., 2007, 4113–4115 | 4115