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R
OH
O
O
R
OH
R
OH
d
n
4
r
4
n
g
|
1
R
R
O
R
O
OH
R
OH
Scheme 1.20 Reaction pathways for the aerobic oxidation of primary alcohols.
.
Figure 1.2 Effect of pressure on the oxidation of benzyl alcohol using CO
2
as
solvent. Reaction conditions: 80 1C, 1.25 g of catalyst (0.5% Pd/Al
2
O
3
);
feed composition: 0.9 mol% benzyl alcohol, 0.45 mol% O
2
, rest CO
2
.
(
K
) Conversion; (D) benzaldehyde selectivity; (
J
) toluene selectivity;
(
'
) selectivity to over-oxidation products.
showed that, depending on the pressure, substrate and products are dis-
tributed differently in the organic and supercritical phases, thus affecting
both the reaction rate and the selectivity (Figure 1.2). Biphasic conditions at
pressures close to the dew point resulted in the highest reaction rate, with
formation of significant amounts of toluene (25%) as a side product,
whereas working in a single phase led to the formation of over-oxidation
products as the dominant side products.
1.4 Nanocatalysis for the Aerobic Oxidation
of Alcohols
Over recent decades, the study of metal nanoparticles - generally so-called
when their size is between 1 and 10 nm - with high specific catalytic activity
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