Mohammad & Mohammad
FULL PAPER
is more polar than the solvent n-heptan or toluene.
Similarly oxides of manganese could be easily oxidized
or reduced at a relatively lower temperature than ZrO2.
Conclusions
The results of the present study uncovered the fact
that Pt/ZrO2 is a better catalyst for catalytic oxidation of
toluene in aqueous solution. It is free from additives,
promoters, and co-catalysts and can easily be separated
from reaction mixture by simple filtration and can be
reused. This gives us reasons to conclude that it is a
possible alternative for the purification of wastewater
containing toluene under mild conditions. Literature
suggests that toluene concentration in industrial waste-
Figure 8 Effect of oxygen partial pressure on the conversion of
toluene in aqueous medium catalyzed by Pt/ZrO2 at 333 K. Reac-
tion conditions: catalyst (100 mg), solution volume (10 mL),
toluene concentration (200— 1000 mg•L ), stirring (900 r/min),
time (30 min).
-
1
water varies between 7—753 mg•L- depending on the
1
type of industry. Optimizing conditions for complete-
oxidation of toluene to benzoic acid in the above
men-tioned range are: time 30 min, temperature 333 K,
agitation 900 r/min, p(O2) ca. 101 kPa, catalyst amount
100 mg. The main advantage of the above optimal con-
dition allows the treatment of wastewater at a lower
temperature (333 K). Among the various models for the
kinetics of surface catalyzed reactions the Eley-Rideal
mechanisms gave a better fit for experimental results.
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Figure 10 Plot of calculated conversion vs. experimental con-
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surface could be envisaged. Ordóñez et al.15 have re-
ported the Mars-van Krevelen mechanism for the deep
oxidation of toluene, benzene and n-hexane catalyzed
by platinum on γ-alumina. However, in that case the
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(E1001265 Sun, H.; Fan, Y.)
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Chin. J. Chem. 2010, 28, 2216— 2220