Oxidation of cyclohexane over Bi-incorporated MCM-41 mesoporous molecular sieve catalyst with oxygen as oxidant

Article abstract of DOI:10.1246/cl.2005.162

Bismuth-incorporated MCM-41, which was directly synthesized under strongly acidic conditions and characterized, for the first time, by XRD, UV-vis and Raman spectroscopy, was used as catalyst for the oxidation of cyclohexane without organic solvent using O₂ as oxidant, and the results of reaction indicate that Bi-MCM-41 is a very stable and efficient catalyst. Copyright

Full text of DOI:10.1246/cl.2005.162

1
62
Chemistry Letters Vol.34, No.2 (2005)
Oxidation of Cyclohexane over Bi-incorporated MCM-41 Mesoporous Molecular Sieve
Catalyst with Oxygen as Oxidant
ꢀ
y
Guang Qian, Gaomeng Lu, Dong Ji, Rui Zhao, Yanxing Qi, and Jishuan Suo
Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, P. R. China
Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, P. R. China
y
(Received September 28, 2004; CL-041141)
Bismuth-incorporated MCM-41, which was directly synthe-
sized under strongly acidic conditions and characterized, for the
first time, by XRD, UV–vis and Raman spectroscopy, was used
as catalyst for the oxidation of cyclohexane without organic sol-
vent using O2 as oxidant, and the results of reaction indicate that
Bi-MCM-41 is a very stable and efficient catalyst.
Oxidation of cyclohexane to cyclohexanol and cyclohexa-
none is a very important industrial process from both economical
1
and environmental aspect. In practice, oxidation of cyclohexane
to cyclohexanol and cyclohexanone is now carried out with air as
oxidant without catalyst or using a cobalt salt catalyst on an in-
dustrial scale worldwide. However, these processes have their
shortages; cyclohexane conversion was lower than 6% and gen-
eral yields of cyclohexanol and cyclohexanone were lower than
Figure 1. The XRD patterns of Bi-MCM-41 catalysts with
different Bi content (A. 6.1 wt %; B. 2.1 wt %; C. 1.4 wt %;
D. 0.55 wt %.)
80%. For these reasons, many catalytic systems have been de-
signed for the oxidation of cyclohexane, wherein various oxi-
dants have been explored and alternative sources of active oxy-
2
,3
4–7
gen, such as iodosobenzene, hydrogen peroxide, alkyhydro-
,6
peroxide,4 NaClO, and O2 (air),
8
4,6,9–14
are used instead of en-
ergy consuming dioxygen activation. Unfortunately, most of
these systems always need a large amount of oxidant or organic
solvent, and from both an economical and environmental view-
point there is a growing demand for atom-efficient catalytic
methods that employ clean oxidants such as O2 (air) without
any organic solvent. But for the oxidation of cyclohexane, the
solvent, which determined the polarity of medium in the reaction
A
B
C
D
Bi O3
2
4
,15
systems, plays an important role in the activity of catalysts.
The development of solvent-free systems is still a challenge
3500
3000
2500
2000
1500
1000
500
0
-
1
Raman shift /cm
4
,10,13,14
and only a few systems were reported.
Figure 2. Raman spectra for the Bi-MCM-41 catalysts and
Bi2O3 (A. 6.1 wt %; B. 2.1 wt %; C. 1.4 wt %; D. 0.55 wt %.)
Recently, some redox molecular sieves such as TS-1, metal-
containing MCM-41, and metal-containing ALPO, VPO were
used as catalysts for oxidation of cyclohexane. However, most
4
,9
of them give low conversions and turnover numbers. More re-
cently, we have reported on the oxidation of cyclohexane using
Au/ZSM-5 as catalyst and O2 as oxidant in a solvent-free sys-
tem.16 The results indicated that Au/ZSM-5 is a very efficient
catalyst for the oxidation of cyclohexane. But it was also found
that gold nanoparticle leaching from the ZSM-5 sieve is quite se-
rious. In further research, therefore, we pay attention to find
more stable and efficient catalyst for oxidation of cyclohexane.
In this paper, we report a highly efficient procedure for oxidation
cyclohexane without any organic solvent using O2 as oxidant
and Bi-incorporated MCM-41 as catalyst, which was directly
þ
synthesized under strongly acidic conditions ([H ] = 6 mol/
L), and characterized, for the first time, by XRD, ICP, UV–vis
DRS, and Raman spectroscopy.
The synthesis of Bi-MCM-41 catalysts is as follows: cetyl
Figure 3. UV–vis spectra for the Bi-MCM-41 catalysts and
Bi O (A. 6.1 wt %; B. 2.1 wt %; C. 1.4 wt %; D. 0.55 wt %.)
2
3
Copyright Ó 2005 The Chemical Society of Japan

Chemistry Letters Vol.34, No.2 (2005)
163
Table 1. Cyclohexane oxidation over Bi-MCM-41 catalysta
analysis indicates that the main by-products contain adipic acid
and some esters. However, no oxidation product was detected by
GC with pure silica MCM-41 as catalyst or in 1.0 MPa Ar (En-
tries 1, 2). After reaction, it was found that the leaching of active
metal in the catalysts is so slight that no bismuth was detected by
ICP in reaction liquid under given reaction conditions. In leach-
ing reaction, firstly cyclohexane was stirred with Bi-MCM-41
T
Sel. / %
Entry
Cat.
Con. / %
/
h
nol
none
b
1
MCM-41
A
5
4
1
2
4
4
4
4
4
4
4
3
4
No reaction
No reaction
No reaction
4
c
2
3
4
5
6
7
8
A
A
A
B
C
D
A
/
45
36
22
19
22
28
54
62
72
72
70
60
(
A) under given conditions, after Bi-MCM-41 was filtrated,
9
12.5
17
12
19.4
the cyclohexane was used as reactant, and no oxidation products
have been detected by GC. The result reconfirms that the leach-
ing of bismuth in the catalysts is very slight (Entries10 and 11),
and this conclusion is also supported by recycling test (Entry 13,
a little decrease in the conversion of cyclohexane could be due to
loss of the catalyst during filtration and no addition of any fresh
catalyst to keep an identical amount of catalyst used.) Compared
with Au/ZSM-5 (Entry 12), obviously, Bi-MCM-41 is a more
stable catalyst.
In summary, this process is highly efficient and environmen-
tal friendly (high conversion and selectivity, clean oxidant with-
out any solvent), and Bi-MCM-41 is found to be a very efficient
catalyst for the oxidation of cyclohexane using oxygen as oxi-
dant in a solvent free system, and it behaves truly as a heteroge-
neous catalyst. The further research is still ongoing.
d
9
e
1
1
1
0
No reaction
No reaction
5
f
1
2
/
Au/ZSM-5
C
e
24
21
ꢁ
68
70
g
1
3
16.8
a
Cyclohexane (18.5 mmol), catalyst (10 mg), 150 C, 1 MPa
b
O2, stirring. Pure silica MCM-41 (10 mg) was used as ‘‘cat-
alyst.’’ Reaction carried out under 1 MPa Ar. Catalyst
40 mg). Leaching reaction: the catalyst A or Au/ZSM-5
Au loading: 1.3 wt %) was separated from the reaction mix-
c
d
e
(
(
ture after 24 h. by filtration under 0.1 MPa air at reaction
temperature and the filtrate was immediately allowed to react
further without catalyst. Leaching reaction: same as e but the
f
References
catalyst (A) was separated from the reaction mixture after 4 h.
by filtration under 1.0 MPa Ar at 150 C. Reaction results for
the third run.
1
2
3
4
A. K. Suresh, M. M. Sharma, and T. Stridar, Ind. Eng. Chem.
Res., 39, 3958 (2000).
J. T. Groves and T. E. Nemo, J. Am. Chem. Soc., 105, 6243
(1983).
T. G. Traylor, J. S. Buyn, P. S. Traylor, P. Battoni, and
D. Mansuy, J. Am. Chem. Soc., 1133, 7821 (1991).
U. Schuchardt, D. Cardoso, R. Sercheli, R. S. da Gruz,
M. C. Guerreiro, D. Mandelli, E. V. Spinac e´ , and E. L. Pires,
Appl. Catal., A, 211, 1 (2001).
ꢁ
g
pyridine bromide (surfactant), deionized water, hydrochloric
acid, and bismuth nitrate were mixed at 323 K and stirred for
30 min. TEOS was added to above mixture with vigorous stirring
to obtain gel mixture. The molar composition of the gel is 0.33
CPBr/1.0 TEOS/7.5 HCl/68 H2O/0.06–0.08 Bi(NO3)3. After
ꢁ
the mixture was stirred for about 24 h at 50 C, the resultant
product was filtered and washed with deionized water, dried at
5
E. L. Pires, U. Arnold, and U. Schuchardt, J. Mol. Catal. A:
Chem., 169, 157 (2001).
ꢁ
ꢁ
1
00 C for 3h., and then calcined in air at 550 C for 6h. The cat-
alytic oxidations were carried out in a stainless steel reactor of
5-mL capacity equipped with a magnetic-type stirrer. In a typi-
6
7
A. Sakthivel and P. Selvam, J. Catal., 211, 134 (2002).
U. R. Pillai and E. Sahle-Demessie, Chem. Commun., 2002,
2142.
2
cal reaction procedure, cyclohexane (18.5 mmol) was mixed
ꢁ
with Bi-MCM-41 catalyst (10 mg) and heated to 150 C in a
8
F. Montanari and L. Casella, ‘‘Metalloprphrins Catalyzed
Oxidation, Kluwer Academic Publisher,’’ London (1994).
J. M. Thomas and R. Raja, Chem. Commun., 2001, 675.
1
MPa O2 atmosphere. After reaction, the reactants and products
were directly analyzed by GC or GC–MS.
9
Figure 1 illustrates the powder X-ray diffraction (XRD) pat-
terns of calcined Bi-MCM-41. As displayed in Figure 1, the
XRD is similar to those reported in the literature indicating that
the mesoporous molecular sieve synthesized had an ordered hex-
agonal cylindrical shape channel system. Figure 2 shows the Ra-
man spectra of Bi-MCM-41 and crystalline Bi2O3. Crystalline
Bi2O3 is a very strong Raman scatterer, so the absence of intense
10 C.-C. Guo, M.-F. Chu, Q. Liu, Y. Liu, D.-C. Guo, and
X.-Q. Liu, Appl. Catal., A, 246, 303 (2003).
11 N. Perkas, Y. Koltypin, O. Palchik, A. Gedanken, and
S. Chandrasekaran, Appl. Catal., A, 209, 125 (2001).
12 N. Perkas, Y. Wang, Y. Koltypin, A. Gedanken, and
S. Chandrasekaran, Chem. Commun., 2001, 988.
13 Y. Ishii, S. Sakaguchi, and T. Iwahama, Adv. Synth. Catal.,
343, 393 (2001).
ꢂ1
peak at ca. 2134, 1723, 1409, 448, and 315 cm (in Bi2O3) in-
dicates that the bismuth was highly dispersed in the silica-based
framework structure. This result is supported by the conclusion
drawed from the UV–vis spectra (Figure 3).
14 N. Savatari, T. Yakota, S. Sakaguchi, and Y. Ishii, J. Org.
Chem., 66, 7889 (2001).
15 E. L. Pires, J. C. Magalhaes, and U. Schuchardt, Appl. Catal.,
A, 203, 231 (2000).
16 R. Zhao, D. Ji, G. Lv, G. Qian, L. Yan, X. Wang, and J. Suo,
Chem. Commun., 2004, 904.
As shown in Table 1, good to excellent conversion and
ꢁ
selectivity were obtained at 150 C in 1.0 MPa O2 over
Bi-MCM-41 catalysts with different bismuth content. GC–MS
Published on the web (Advance View) December 25, 2004; DOI 10.1246/cl.2005.162