272
CAMBLOR ET AL.
while, H-Beta-D performs the Beckmann rearrangement
of 1b and 1c very well.
2. Sato, S., Urabe, K., and Izumi, Y., J. Catal. 102, 98 (1986).
3. Curtin, T., McMonagle, J. B., and Hodnett, B. K., Catal. Lett. 17, 145
(1993).
Since H-ZSM-5 and H-Beta-D have similar Bro¨nsted
acidity (see Table 2), the differences in activity are prob-
ably related to geometrical effects due to the differences
in pore dimensions. Indeed, ZSM-5 zeolite has a pore size
of 0.55 nm, while Beta has a pore size of 0.7 nm. Thus,
the bulkier acetophenone oxime (0.7 nm) is barely able to
diffuse inside the pores; an important contribution of the
sites at the external surface takes place, as can be seen from
the lower selectivity to the amide obtained with this reac-
tant on H-ZSM-5. In the case of cyclododecanone oxime
(0.9 nm), it is already too large to react on H-ZSM-5, and
this zeolite becomes inactive. In the case of Beta, there are
problems related to the diffusion of the cyclododecanone
oxime, and, consequently, the contribution of the external
surface to the total activity should become more important
decreasing therefore the selectivity to the amide (Table 5).
There is no doubt that the selectivity could be improved by
silanizing the external silanol groups.
4. Gutierrez, E., Aznar, A. J., and Ruiz-Hitsky, E., Stud. Surf. Sci. Catal.
59, 539 (1995).
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105, 1173 (1996).
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(1996).
8. Ushikudo, T., and Wada, K., J. Catal. 148, 138 (1994).
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(1992).
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22, 187 (1986).
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Chem. Commun., 1071 (1996).
14. Sato, H., Ishii, N., Hirose, K., and Nakamura, S., Stud. Surf. Sci.Catal.
28, 755 (1986).
15. Sato, H., Hirose, K., and Nakamura, S., Stud. Surf. Sci.Catal. 49, 1213
(1989).
16. Sato, H., Hirose, K., and Nakamura, S., Chem. Lett., 1987
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CONCLUSIONS
17. Yashima, T., Miura, K., and Komastu, T., Stud. Surf. Sci. Catal. 84, 1897
(1994).
We have proven that external silanol groups present in 18. Ho¨lderich, W. F., Stud. Surf. Sci. Catal. 46, 193 (1989).
19. Singh, P. S., Bandyopadhayay, R., Hegde, S. G., and Rao, B. S., Appl.
Catal. 136, 249 (1996).
20. Dai, L. X., Hayasaka, R., Iwaki, Y., and Tatsumi, T., Sogo Shikensho
zeolites may be active when the reaction is carried out at
moderate temperatures in the liquid phase, and thus the
oxime is hydrolyzed to give the corresponding ketone. On
Nenpo (Tokyo Daigaku, Kogakubu) 55, 159 (1996).
the other hand, internal silanols are active and selective for
performing the Beckmann rearrangement (33). This may
be due to a higher acidity of the internal silanols, compared
to the external silanols and/or to the preactivation of the
oxime in the pore of the zeolite. Under the same reaction
conditions, Bro¨nsted acid sites are very active and selective
for the formation of the amide. Finally, properly prepared
Beta zeolite is suitable for carrying out the Beckmann rear-
rangement of large size oximes, such as acetophenone and
cyclododecanone oximes.
21. Reddy, J. S., Ravishankar, R., and Ratnasamy, P., Catal. Lett. 17, 139
(1993).
22. Bell, W. K., and Chang, C. D., Europ. Patent 056 698 (1985).
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24. Olson, K. D., E.P. 251 168 (1988).
25. Fajula, F., E.P. 0 488 867 A1 (1991).
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27. Camblor, M. A., Corma, A., and Valencia, S., Chem. Commun., 2365
(1996). [Blasco, T., Camblor, M. A., Corma, A., Esteve, P., Guil, J. M.,
Mart´ınez, A., Perdigo´n-Melo´n, J. A., and Valencia, S., J. Phys Chem.
B 102, 75 (1998).]
28. Camblor, M. A., Corma, A., and Valencia, S., manuscript in prepara-
tion.
ACKNOWLEDGMENT
29. Camblor, M. A., Corma, A., Mifsud, A., Pe´rez-Pariente, J., and
Valencia, S., Stud. Surf. Sci. Catal. 105, 341 (1997).
30. Van Santen, R. A., private communication.
31. Corma, A., Zicovich-Wilson, C. M., and Viruela, P., J. Phys. Chem. 98,
10863 (1994).
Financial support by the Spanish MAT97-1016-C02-01 is gratefully
acknowledged.
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