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ratio will depend on the relative rates of diffusion of the
regioisomers. It has been demonstrated that the diffusion of the
para isomer of ethyltoluene in the pores of a zeolite can be
several orders of magnitude higher than that of the bulkier
ortho and meta isomers.20 The more slowly moving ortho and
meta isomers remain within the zeolite and once the para
isomer is generated as a result of the random isomerization that
occurs under the inuence of the acidic catalyst it rapidly
diffuses out. The net result is that the relative amount of para-
ethyltoluene can become very high and the relative amount of
ortho-ethyltoluene, which is the most voluminous and therefore
the most slowly diffusing isomer, virtually zero. Table 2 show
that the ortho to meta to para ratio did not differ dramatically for
the two types of catalysts. Thus, the large pores in the micro-
porous/mesoporous material did not result in a higher relative
yield of the more bulky ortho and meta isomers. For the catalyst
with mesopores there was a substantial increase in the meta to
para ratio with an increase in temperature. This is in agreement
with previously reported trends.7a Reactions over the regular
microporous catalyst gave almost the same meta to para ratio at
the different temperatures, however. The effect of the ethene
ow rate was investigated for microporous/mesoporous HZSM-
5 at 375 ꢀC. As can be seen in Table 2, neither the conversion of
toluene, nor the product composition was much inuenced by
this parameter under the conditions studied.
Notes and references
1 S. Kulprathipanja, Microporous Zeolites in Industrial Catalysis
and Separation, Wiley-VCH Verlag GmbH, Weinheim, 2010.
2 (a) M. Guidotti, C. Canaff, J. M. Coustard, P. Magnoux and
M. Guisnet, J. Catal., 2005, 230, 375; (b) E. G. Derouane,
C. J. Dillon, D. Bethell and S. B. Derouane-Abd Hamid, J.
Catal., 1999, 187, 209; (c) M. E. Davis, Nature, 2002, 417, 813.
3 (a) R. Srivastava, M. Choi and R. Ryoo, Chem. Commun., 2006,
¨
4489; (b) A. Taguchi and F. Schuth, Microporous Mesoporous
¨
Mater., 2005, 77, 1; (c) Z. Bohstrom, I. Rico-Lattes and
K. Holmberg, Green Chem., 2010, 12, 1861; (d) Z. Bohstrom,
J. Porous Mater., 2012, 19, 921; (e) Z. Bohstrom and
K. Holmberg, J. Mol. Catal. A: Chem., 2013, 366, 64.
4 Y. Han, N. Li, L. Zhao, D. Li, X. Xu, S. Wu, Y. Di, C. Li, Y. Zou,
Y. Yu and F.-S. Xiao, J. Phys. Chem. B, 2003, 197, 7551.
5 F.-S. Xiao, L. Wang, C. Yin, K. Lin, Y. Di, J. Li, R. Xu, D. Su,
¨
¨
¨
R. Schlogl, T. Yokoi and T. Tatsumi, Angew. Chem., Int. Ed.,
2006, 45, 3090.
6 (a) Z. Yang, Y. Xia and R. Mokaya, Adv. Mater., 2004, 16, 727;
(b) H. C. Li, Y. Sakamoto, Z. Liu, T. Ohsuna, O. Terasaki,
M. Thommes and S. Che, Microporous Mesoporous Mater.,
2007, 106, 174; (c) Y. M. Fang and H. Q. Hu, J. Am. Chem.
Soc., 2006, 128, 10636; (d) W.-C. Li, A.-H. Lu, R. Palkovits,
¨
W. Schmidt, B. Spliethoff and F. Schuth, J. Am. Chem. Soc.,
2005, 127, 12595; (e) R. Srivastava, N. Iwasa, S.-I. Fujita and
M. Arai, Chem.–Eur. J., 2008, 14, 9507; (f) H. Wang and
T. J. Pinnavaia, Angew. Chem., Int. Ed., 2006, 45, 7603; (g)
M. Choi, H. S. Cho, R. Srivastava, C. Venkatesan, D. Choi
and R. Ryoo, Nat. Mater., 2006, 5, 718; (h) K. Egeblad,
M. Kustova, S. K. Klitgaard, K. Zhu and C. H. Christensen,
Microporous Mesoporous Mater., 2007, 101, 214.
7 (a) J. Cejka, B. Wichterlov and S. Bednarova, Appl. Catal., A,
1991, 79, 215; (b) S. Rummel, S. M. Yunusov, H. Langguth
and V. B. Shuth, Russ. Chem. Bull., 1999, 48, 2083.
8 L. Wang, Z. Zhang, C. Yin, Z. Shan and F.-S. Xiao,
Microporous Mesoporous Mater., 2010, 131, 58.
9 P. Punyapalakul, S. Soonglerdsongpha, C. Kanlayaprasit,
C. Ngamcharussrivichai and S. Khaodhiar, J. Hazard.
Mater., 2009, 171, 491.
10 S. Brunauer, P. H. Emmett and E. Teller, J. Am. Chem. Soc.,
1938, 60, 309.
Conclusion
The microporous/mesoporous HZSM-5 catalyst gave a slightly
higher conversion than the conventional microporous zeolite in
the Friedel–Cras alkylation of toluene with ethene. The yield of
ethyltoluene was also somewhat higher with the former catalyst.
For both catalysts the yield went through a maximum around
375 ꢀC. The difference in yield obtained with the two catalysts
increased with increasing temperature. This indicates that clog-
ging of the pores with carbonaceous material is a deactivation
mechanism at higher temperature. A catalyst that contains mes-
opores is likely to be more resistant to clogging than a catalyst
that only contains micropores. Catalytic cracking of the products
formed, i.e. ethyl- and diethyltoluene, is another possible reason
for the decrease in yield at higher temperature. One might have
expected the catalyst with mesopores to give a higher ratio of
dialkylation to monoalkylation but this was not the case. On the
contrary, the mesopore-containing catalyst gave a slightly higher
selectivity for monoalkylation than the catalyst with only micro-
pores. There was an interesting difference in regioselectivity for
the two catalysts. Whereas the microporous zeolite gave a rela-
tively constant meta to para ratio over the temperature interval
studied, the meta to para ratio went from 48 : 52 at 325 ꢀC to
11 E. P. Barrett, L. G. Joyner and P. P. Halenda, J. Am. Chem.
Soc., 1951, 73, 373.
12 (a) A. Hinz, M. Skoglundh, E. Fridell and A. Andersson,
˚
J. Catal., 2001, 201, 247; (b) H. H. Ingelsten, A. Hildesson,
E. Fridell and M. Skoglundh, J. Mol. Catal. A: Chem., 2004,
209, 199.
13 S. Z. Chen, K. Huddersman, D. Keir and L. V. C. Rees,
Zeolites, 1988, 8, 106.
ꢀ
59 : 32 at 400 C for the microporous/mesoporous zeolite. Both
catalysts gave very small yield of the ortho isomer.
14 K. S. W. Sing, D. H. Everett, R. A. W. Haul, L. Moscou,
R. A. Pierotti, J. Rouquerol and T. Siemieniewska, Pure
Appl. Chem., 1985, 57, 603.
15 (a) Z.-M. Wang, M. Yamaguchi, I. Goto and M. Kumagai,
Phys. Chem. Chem. Phys., 2002, 2, 3007; (b)
A. A. Tsyganenko, D. V. Pozdnyakov and V. N. Filimonov,
Acknowledgements
Cecilia Thorstensson at AkzoNobel Surface Chemistry is
acknowledged for help with the GC-MS analysis. The Swedish
Research Council is acknowledged for nancial support.
28792 | RSC Adv., 2014, 4, 28786–28793
This journal is © The Royal Society of Chemistry 2014