KINETICS OF THE REDUCTION OF
p
ꢀNITROBENZOIC ACID ESTERS
373
10 , cm3/g
−
3
The polymers containing nanodisperse palladium
were prepared by the procedure [9]. The palladium
content in the polymers was 0.02 g per 1 g of dry polyꢀ
V
×
2
1
1
0
1
mer; the dispersity of metallic palladium was 25
±
1
2
2
3
4
4
5
'
'
5
nm according to XRD data [9].
Reaction (1) was studied at a gas pressure of 1.013
×
5
1
0–5 Pa at temperatures of 303–328 K. Hydrogenation
was performed by the procedure [10]. To prevent the
side process of reꢀesterification, methyl, ethyl, and proꢀ
pyl esters were hydrogenated in methanol, ethanol, and
propanol, respectively. Nitrobenzene was hydrogenated
0
5
0
'
in ethanol; pꢀnitrobenzoic acid was hydrogenated in
water at 338 K. The activation energy was calculated by
the Van’t Hoff equation. The atomic charges were calꢀ
culated using the MOPACꢀ2009, Chem3DUltra proꢀ
gram and the Wang–Ford procedure.
0
20
40
60
80
t
, min
RESULTS AND DISCUSSION
As is known, reduction (1) of aromatic nitro comꢀ
pounds occurs in three stages [11]:
Fig. 1. Time dependences of hydrogen absorption during
the reduction of nitro compounds in the presence of pallaꢀ
diumꢀcontaining (
and ( ', ', ') KUꢀ23: (
nitrobenzene; ( ) methyl, (
ꢀnitrobenzoic acid esters.
1
–
5
) sulfonated polycalixresorcinarene
') ꢀnitrobenzoic acid; ( ')
') ethyl, and ( ) propyl
ArNO +H = ArNO+H O
,
(2)
(3)
(4)
2
2
2
1
2
4
1,
1
p
,
2, 2
3
4
4
5
ArNO+H = ArNHOH
,
2
p
ArNHOH+H = ArNH +H O
.
2
2
2
Reaction (2) was assumed to be the limiting stage of
process (1). Then the transformation rate is probably
determined either by the slow recombination of the
adsorbed hydrogen molecule
the procedure [4]. Sulfonated polycalixresorcinarene
has a gel structure containing two kinds of ionogenic
groups—phenolic OH and SO H groups. The total
3
dynamic ionꢀexchange capacity is 5.65 mgꢀequiv/g of
the polymer H form; the sulfo group capacity is
H → H (ads.) → H(ads.) + H(ads.)
,
(5)
2
2
2
.45 mgꢀequiv/g [7]. The macroporous sulfocationite
or by the diffusion of the reactant components for colꢀ
lision with the catalyst in the polymer phase.
Let us consider both mechanisms of (1). The diffuꢀ
sion and process (5) are characterized by different
activation energies. For (5), the activation energy is
expected to be comparable to the H–H bond cleavage
KUꢀ23 30/100 contains SO H groups; its total ionꢀ
exchange capacity is 3.8 mgꢀequiv/g of the polymer H
form [8].
3
Kinetic characteristics of the hydrogenation of nitro comꢀ
pounds in the presence of sulfonated polycalixresorcinarene
and sulfocationite KUꢀ23 30/100 at 308 K
(
432 kJ/mol [12]). Figure 1 shows the kinetic curves of
the reduction of nitrobenzene,
and methyl, ethyl, and propyl
p
ꢀnitrobenzoic acid,
ꢀnitrobenzoic acid
p
Compound
Sulfocationite KUꢀ23 30/100
–0.445 –0.445 10.7 ± ±0.6
qO8
qО14
a
×
103
E
esters in the presence of palladiumꢀcontaining netꢀ
work polymers (sulfocationite KUꢀ23 30/100 and sulꢀ
fonated polycalixresorcinarene) at 308 K. The characꢀ
teristics of the hydrogenation of the nitro compounds
on palladiumꢀcontaining polymers at 308 K are preꢀ
sented in the table. The kinetic characteristics (Fig. 1
and table) of (1) show that the hydrogenation of the
ArNO2
–
C H OOCArNO –0.436 –0.432 11.2 ± ±1.5 24.4
5
2
2
HOOCArNO2
Sulfonated polycalixresorcinarene
–0.430 –0.431 2.7 ± ±1.0 32.8
nitro group in
pꢀnitrobenzoic acid esters occurs at high
rates under mild conditions. At a gas pressure of
–5
ArNO2
CH OOCArNO
–0.445 –0.445 4.9 ± ±0.8 22.5
–0.430 –0.435 3.7 ± ±0.5 45.0
1.013
×
10 Pa and a temperature of 308 K, the cataꢀ
lytic activity of palladiumꢀcontaining network polyꢀ
3
2
–
3
–3
mers is 1.2
×
10 to 11 10 mol of H /(min g of Pd).
2
±
×
C H OOCArNO –0.436 –0.432 7.0 ± ±1.0 38.3
2
5
2
The activation energy is 35 10 kJ/mol (table).
C H OOCArNO –0.433 –0.436 8.1 ± ±1.8 29.7
2
According to our experimental data, the reduction
of nitro compounds in the presence of polymer nanoꢀ
composites containing nanodisperse palladium is a
3
7
HOOCArNO2
–0.430 –0.431 1.2 ± ±0.2 25.7
qi is the charge on the ith atom; a is the catalytic activity, mol of first order process with respect to hydrogen. Palladium
H /(min g of Pd); and E is the activation energy, kJ/mol.
2
remains at the zero oxidation level during hydrogenaꢀ
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
Vol. 89
No. 3 2015