CATALYTIC PROPERTIES OF THE CrꢀHMS MATERIALS IN THE BENZYLATION
53
Table 5. Effect of recycling of the catalysts in the benzylation of benzene with benzyl chloride at 353 K over CrꢀHMSꢀ15
catalyst (Bz/BzCl = 15 and mcat = 0.1 g)
Selectivity, %
Apparent rate constant
Ka, 10 min
Running
Fresh
Time*, min
4
–1
diphenylmethane
polybenzyl chlorides
427.1
447.3
459.8
80.6
81.5
79.3
19.4
18.5
20.7
132.8
129.5
130.7
First run
Second run
*
Time required for the complete conversion of benzyl chloride.
zene benzylation process without a significant change 12. Cao, J., He, N., Li, C., Dong, J., and Xu, Q., Mesopoꢀ
rous Mol. Sieves, 1998, vol. 117, p. 461.
of its catalytic activity.
1
3. Choudhary, V.R., Jana, S.K., and Mamman, A.S.,
In conclusion, mesoporous catalysts CrꢀHMSꢀ
were synthesized with different Cr content and exhibꢀ
n
Microporous Mesoporous Mater., 2002, vol. 56, p. 65.
ited excellent activities in the benzylation of benzene 14. He, N., Bao, S., and Xu, Q., Appl. Catal., A, 1998,
and substituted benzenes reaction. XRD, DR UV–vis
and H ꢀTPR characterizations demonstrate that
chromium content in CrꢀHMSꢀn has significant effect
vol. 169, p. 29.
2
15. Bachari, K., Millet, J.M.M., Benaichouba, B., Cherꢀ
ifi, O., and Figueras, F., J. Catal., 2004, vol. 221, p. 55.
on oxidation state and coordination of chromium speꢀ
cies. Cr (VI) species corresponding to chromate form
the main local structure of chromium at low Cr conꢀ
tent. The percentage of Cr (VI) decrease and crystal
Cr O appear with an increase of Cr loading. Two
kinds of Cr (VI) with different reduced abilities are difꢀ
ferentiated by H2ꢀTPR method. Furthermore, the
mechanism involves probably a redox step at the reacꢀ
tion initiation. This gives a greater independence to
1
1
1
6. Choudhary, V.R. and Jana, S.K., Appl. Catal., A, 2002,
vol. 224, p. 51.
7. Choudhary, V.R., Jana, S.K., and Narkhede, V.S., Appl.
Catal., A, 2002, vol. 235, p. 207.
2
3
8. El Berrichi, Z., Cherif, L., Orsen, O., Fraissard, J., Tesꢀ
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,
2
water.
2
2
2
0. Choudhary, V.R. and Jana, S.K., J. Mol. Catal. A:
Chem., 2002, vol. 180, p. 267.
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KINETICS AND CATALYSIS Vol. 52
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2011