M. S. Saha et al. / Tetrahedron Letters 44 (2003) 5535–5537
5537
when the initial concentrations of acetic acid and
hydrogen peroxide were 1.65 and 2.85 M, respectively
(run 4). In this case, the conversion of acetic acid into
PAA was 16% which is considerably large, compared
with that of run 1.
The concentration of PAA solution prepared by the
batchwise operation was increased with the reaction
time and it was ca. 3.5 mM when the reaction time was
7 h, and at 17 h and longer reaction time it was almost
constant (ca. 4.1 mM) (Fig. 2), which is considered as
the equilibrium concentration of PAA under the prepa-
ration conditions used here.
Figure 3. Dependence of the concentration of PAA upon the
loading amount of Nafion-H catalyst at 25°C. Initial concen-
trations: [CH3COOH]=1.65 M and [H2O2]=2.85 M; reaction
time: 17 h.
To examine reusability of the catalyst, the experiment
was carried out using the used Nafion-H catalyst. Run
2 is the result for the used catalyst of Nafion-H and is
comparable to run 1 for the fresh catalyst. The catalyst
used in run 1 was immersed in 20% HNO3 for 4–5 h at
room temperature and then filtered. After that, the
catalyst was washed several times with deionzed water
until a neutral filtrate was obtained and finally was
dried under vacuum at 105°C for at least 10 h. The
comparison of runs 1 and 2 indicates that the catalytic
activity of the regenerated Nafion-H is as good as that
of the fresh one.
products and used repeatedly without a decrease in the
catalytic activities.
References
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The dependence of the concentration of PAA upon the
loading amount of Nafion-H catalyst is shown in Fig-
ure 3. The reaction time was 17 h. The production of
PAA was observed to increase with increasing the
loading amount of Nafion-H and PAA of ca. 0.3 M
was prepared when its loading was 10%.
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Figure 2. The concentration of PAA produced by the batch-
wise operation as a function of the reaction time using
Nafion-H. Catalyst loading: 5 wt%; initial concentrations:
[CH3COOH]=0.5 M and [H2O2]=0.378 M; temperature:
25°C.
17. Nafion is the trade name of E.I. DuPont de Nemours &
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