Vol. 26, No. 9 (2014)
Direct Hydroxylation of Benzene to Phenol Over Pyridine-Modified Vanadium-Substituted Heteropoly Acid 2685
and the results is shown in Fig. 4. No phenol was detected
without the use of the Py3PMo11V, which indicated that
Py3PMo11V is essential for performing the reducer. The yield
of phenol was increased from 0 to 24.7 % with the increase
amount of the Py3PMo11V. When amount of the Py3PMo11V is
0.15 g, the yield of phenol reached 24.7 % with a selectivity
of 100 %. But further increase in the amount of the Py3PMo11V
inversely caused a decrease in the yield of phenol. Therefore,
0.15 g Py3PMo11V is considered as a suitable amount in this
reaction.
Conclusion
Coupled conventionally heated method gives phenol yield
of 7.8 %, Py3PMo11V exhibits higher activity for the hydroxy-
lation of benzene with 100 % selectivity of phenol and 24.7 %
phenol yield under microwave irradiation at the optimum
reaction conditions: 1.0 mL benzene, 0.15 g catalyst, 1.8 mL
30 % aqueous solution of H2O2, 15 mL acetonitrile, 70 ºC
reaction temperature and 20 min reaction time.
Analysis the results, concluded that the substituted vana-
dium atom with high dielectric loss factor in heteropoly acid,
can couple easily with microwave energy and gets heated,
is essentially active site with higher performance for the
hydroxylation of benzene to phenol under microwave irra-
diation.
25
20
15
10
5
REFERENCES
1. T. Sakamoto, T. Takagaki, A. Sakakura, Y. Obora, S. Sakaguchi and Y.
Ishii, J. Mol. Catal. A, 288, 19 (2008).
2. Y.-Y. Gu, X.-H. Zhao, G.-R. Zhang, H.-M. Ding and Y.-K. Shan, Appl.
Catal. A., 328, 150 (2007).
3. M. Tani, T. Sakamoto, S. Mita, S. Sakaguchi andY. Ishii, Angew. Chem.
Int. Ed., 44, 2586 (2005).
4. E. Battistel, R. Tassinari, M. Fornaroli and L. Bonoldi, J. Mol. Catal.
A, 202, 107 (2003).
0
0.05
0.10
0.15
0.20
5. C. Gabriel, S. Gabriel, E.H. Grant, E.H. Grant, B.S.J. Halstead and D.M.P.
Mingos, Chem. Soc. Rev., 27, 213 (1998).
Amount of Py3PMo11V (g)
Fig. 4. Effect of catalyst amount on the yield of phenol. Reaction
conditions: 1 mL benzene, 1.8 mL H2O2, 15 mL acetonitrile, 70 ºC,
time 20 min
6. K. Takahashi, T. Okuhara and M. Misono, Chem. Lett., 841 (1985).
7. M. Misono, T. Okuhara, T. Ichiki and Y. Kanda, J. Am. Chem. Soc.,
109, 5535 (1987).
8. B. Xu, Y. Wei, C.L. Barnes and Z. Peng, Angew. Chem. Int. Ed., 40,
2290 (2001).
Effect of the reaction time on the yield of phenol under
microwave irradiation: The influence of reaction time on
the yield of phenol over Py3PMo11V is shown in Fig. 5. It can
be observed that the yield of phenol was a sharply increased
to 24.7 % with the increased of reaction time up to 20 min.
However, the yield decreased with the further increase of
reaction time, which is due to the further oxidation of phenol.
So 20 min is chosen as a suitable reaction time in this work.
9. Y.Y. Liu, K. Murata and M. Inaba, Catal. Commun., 6, 679 (2005).
10. B.B. Bardin and R.J. Davis, Appl. Catal. A, 185, 283 (1999).
11. H.Q. Ge, Y. Leng, F.M. Zang, C.J. Zhou and J. Wang, Catal. Lett., 124,
250 (2008).
12. F.M. Zhang, J. Wang, C.S. Yuan and X.Q. Ren, Catal. Lett., 102, 171
(2005).
13. G. Bond, R.B. Moyes and D.A. Whan, Catal. Today, 17, 427 (1993).
14. P. Lidström, J. Tierney, B. Wathey and J. Westman, Tetrahedron, 57,
9225 (2001).
25
20
15
10
5
5
10
15
20
25
Reaction time (min)
Fig. 5. Effect of reaction time on the yield of phenol. Reaction conditions:
0.15 g catalyst, 1 mL benzene, 1.8 mL H2O2, 15 mL acetonitrile,
70 ºC