Ch. Ramesh Kumar et al. / Journal of Molecular Catalysis A: Chemical 350 (2011) 83–90
89
alcohol molar ratio. Formation of dibenzylether is expected with
high benzyl alcohol concentration due to relatively low rates of
benzylation compared to that of dehydration.
o-
p-
Ether
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
3.2.6. Stability/leaching of the catalyst
After completion of the reaction where the conversion of benzyl
alcohol is complete, the catalyst was separated from the reaction
mixture by centrifugation. To the reaction mixture (filtrate) cal-
culated amount of benzyl alcohol was added and the reaction is
carried out (without addition of catalyst) to check whether any
leaching of the active content (AlTPA) from the support in to reac-
tion mixture. The reaction was continued for a period of 4 h. There
was no conversion of benzyl alcohol. This study reiterates that there
was no leaching of active component during the reaction and the
reaction is taking place on the surface of the catalyst.
4. Conclusions
80
100
120
140
Al exchanged TPA supported on TiO2 catalysts were prepared
with retention of Keggin ion structure of AlTPA. Exchange of TPA
protons with Al ions results in the generation of Lewis acidic sites.
Benzylation activity of anisole depends on the acid strength dis-
tribution and total acidity of the catalysts which related to the
content of AlTPA on support. The optimum loading of AlTPA was
20 wt% for high benzylation activity. Role of support in benzyla-
tion activity also studied by supporting AlTPA on different supports
and their activity was in the following order: 20% AlTPA/TiO2 > 20%
AlTPA/SnO2 > 20% AlTPA/ZrO2 > 20% AlTPA/Nb2O5. The catalyst was
stable during reaction without any leaching of active content. The
benzylation activity and selectivity towards benzylated products
also depend on the reaction temperature, catalyst weight and par-
ticularly on the anisole to benzyl alcohol ratio.
Reaction temperature (ºC)
Fig. 11. Effect of reaction temperature on the conversion of benzyl alcohol.
o-
p-
Ether
100
90
80
70
60
50
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90
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60
50
Acknowledgement
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30
20
10
0
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30
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0
Ch. Ramesh Kumar thanks Council of Scientific and Industrial
Research (CSIR), India, for financial support in the form of a Senior
Research Fellowship.
References
50
100
150
200
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3.2.5. Effect of molar ratio of anisole to benzyl alcohol
Table 2 shows the effect of anisole to benzyl alcohol ratio on
the benzylation activity. The conversion of benzyl alcohol increased
with increase in molar ratio from 1.5 to 15. Selectivity towards ben-
zylated product also improved with increase in anisole to benzyl
Table 2
Effect of anisole to benzyl alcohol molar ratio on benzylationof anisole.
Anisole to benzyl
alcohol ratio
Conversion of
benzyl alcohol (%)
Selectivity (%)
o-
p-
Ether
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1.5
3
15
13.0
90.6
98.2
19.5
37.1
47.1
27.1
41.6
48.8
53.5
21.3
4.1