Use of ozone for preparing 4-nitrobenzoic acid in a closed process cycle

Article abstract of DOI:10.1023/A:1014802612863

The possibility of preparing 4-nitrobenzoic acid in a closed process cycle by oxidation of 4-nitrotoluene with an ozone air mixture was examined. The optimal conditions of oxidation with multiple use of mother liquors were found, and the conditions for crystallization of 4-nitrobenzoic acid from the reaction mixture were determined. The effects of water, acetic anhydride, and catalyst on the oxidation performed in mother liquors after filtration of the target product were examined.

Full text of DOI:10.1023/A:1014802612863

Russian Journal of Applied Chemistry, Vol. 74, No. 10, 2001, pp. 1777 1779. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 10, 2001,
pp. 1721 1723.
Original Russian Text Copyright
2001 by Galstyan, Tyupalo, Patapenko, Andreev.
BRIEF
COMMUNICATIONS
Use of Ozone for Preparing 4-Nitrobenzoic Acid
in a Closed Process Cycle
A. G. Galstyan, N. F. Tyupalo, E. V. Patapenko, and P. Yu. Andreev
Rubezhnoe Branch, East Ukrainian National University, Rubezhnoe, Lugansk oblast, Ukraine
Received June 7, 2001
Abstract The possibility of preparing 4-nitrobenzoic acid in a closed process cycle by oxidation of 4-nitro-
toluene with an ozone air mixture was examined. The optimal conditions of oxidation with multiple use of
mother liquors were found, and the conditions for crystallization of 4-nitrobenzoic acid from the reaction mix-
ture were determined. The effects of water, acetic anhydride, and catalyst on the oxidation performed in
mother liquors after filtration of the target product were examined.
4
4-Nitrobenzoic acid is widely used in production
of organic intermediates, dyes, and drugs [1]. In in-
taining 4.7 10 M ozone was fed at a rate of
3
1
8.3 10 l s . Oxidation was performed until com-
dustry, it is produced by oxidation of 4-nitrotoluene plete exhaustion of 4-nitrotoluene and was monitored
with potassium dichromate in sulfuric acid [2], with
dilute nitric acid [3], and with atmospheric oxygen
in the presence of catalysts (metals of variable oxida-
tion state and bromine compounds) [4]. Oxidation by
mineral oxidants occurs under mild conditions but
yields large amounts of toxic and difficult-to-utilize
wastes. Oxidation by atmospheric oxygen occurs
under rigorous conditions and, therefore, requires
sophisticated equipment. In this context, low-tem-
perature reaction of ozone with 4-nitrotoluene in
acetic acid shows promise. In the presence of cobalt
bromide catalyst, oxidation of 4-nitrotoluene by
ozone air mixture occurs under mild conditions (at-
mospheric pressure, 95 C), and the yield of 4-nitro-
benzoic acid reaches 96% [5].
by GLC [6].
After oxidation, the reaction mixture was cooled
to 13 14 C, and the precipitated carboxylic acid was
filtered off, washed on the filter with hydrochloric
acid, and recrystallized from water; yield 96%. The
filtrate was returned to the oxidation stage. The wash
In this study, we developed a closed process cycle
for production of 4-nitrobenzoic acid by oxidation of
4-nitrotoluene.
EXPERIMENTAL
Fig. 1. Oxidation of 4-nitrotoluene by ozone oxygen mix-
Oxidation of 4-nitrotoluene was performed in a
vertical cylindrical reactor equipped with a blade
stirrer (7.5 13.3 rps) and a bubbler. The reactor was
charged with 40 ml of glacial acetic acid, 4-nitrotolu-
ene (0.5 M), cobalt(II) acetate (0.195 M), and potas-
sium bromide (0.084 M). The stirring was switched
on, and the mixture was heated to 95 C. After dis-
solution of the catalyst, an ozone air mixture con-
4
ture in mother liquor. [ArH] = 0.5, [O ] = 4.7 10
,
3
[CoAc ] = 0.0195, [KBr] = 0.084 M; T = 95 C; the same
2
for Fig. 2. (C) Water concentration and ( ) time. Concen-
tration of (1 4) 4-nitrotoluene and (1 4 ) 4-nitrobenzoic
acid. Runs in the cycle: (1, 1 ) first; (2, 2 ) second with full
catalyst loading; (3, 3 ) third with full catalyst loading;
and (4, 4 ) second with addition of 0.495 M (CH CO) O,
3
2
0.01 M CoAc , and 0.063 M KBr.
2
1070-4272/01/7410-1777 $25.00 2001 MAIK Nauka/Interperiodica

1778
GALSTYAN et al.
Then we studied the effect of the crystallization
time at 14 C. Below are given the crystallization time
(min) and acid yields (%): 0, 52; 3, 60; 6, 70; 10, 78;
15, 78; and 20, 78. Thus, it is appropriate to perform
crystallization for 10 min.
After keeping for 10 min, 4-nitrobenzoic acid was
washed with concentrated HCl to remove the absorbed
cobalt(II) acetate. After fivefold use in the washing
stage, hydrochloric acid was distilled off, and cobalt
chloride was used in the oxidation stage without addi-
tional treatment.
When we used the filtrate from crystallization of
the target product as the solvent, we noticed a pro-
gressing decrease in the accumulation rate and yield
of the aromatic acid with increasing number of re-
cycles (Fig. 1). This might be due to partial loss of
the catalyst. However, even addition of a full portion
of the catalyst in experiments with the filtrate had no
noticeable effect on the oxidation results (Fig. 1, sec-
ond and third runs of the cycle).
Fig. 2. Effect of water on (1) accumulation rate and
(2) yield of 4-nitrobenzoic acid. (v) Accumulation rate,
( ) yield, and (C) water concentration.
waters containing cobalt(II) chloride were evaporated,
and the cobalt(II) salt was used as the reaction catalyst.
To optimize the crystallization conditions, we pre-
pared standard mixtures consisting of 4-nitrobenzoic
acid, cobalt(II) acetate, potassium bromide, and acetic
acid taken in the same amounts as in the experiment
on 4-nitrotoluene oxidation. The reaction solution
obtained at 95 C was cooled with slow stirring.
We found that the optimal conditions of quantitative
isolation of 4-nitrobenzoic acid are cooling from 95
The oxidation deceleration may also be due to for-
mation of oxidation inhibitors: phenols, nitrobenzene,
and water. The effect of inhibitors on the oxidation
was studied after compensating for the partial loss of
the catalyst in the previous run. We found that the rate
of 4-nitrotoluene oxidation in the presence of phenol
and nitrobenzene does not change noticeably, whereas
addition of water appreciably decreases the oxidation
rate and the process selectivity (Fig. 2). Therefore,
under conditions of multiple use of the filtrate, when
the content of water formed by the reaction increases
from run to run, the oxidation selectivity will de-
crease.
1
to 35 C at a rate of 1 deg min and from 30 to 14 C
1
at a rate of 0.5 deg min . With this schedule, 30
60- m crystals of the acid are formed.
Oxidation of 4-nitrotoluene by an ozone oxygen mixture
in a closed process cycle (95 C)*
Degree
of ozone
utilization, % yield, %
4-Nitrobenzoic acid
Run
no.
To bind the water formed by the reaction, we per-
formed experiments with addition of acetic anhydride.
We found that at a concentration of acetic anhydride
in the primary filtrate of 0.495 M (provided that the
catalyst loss is compensated for, see table), the oxida-
tion rate becomes equal to the rate of 4-nitrotoluene
oxidation in glacial acetic acid, and the yield of the
aromatic acid reaches 93%. Further increase in the
concentration of acetic anhydride decreases the oxida-
tion rate and selectivity, because, when the water
formed by the reaction is completely bound, excess
acetic anhydride starts to react with intermediate 4-ni-
trobenzaldehyde to form 4-nitrobenzylidene diacetate,
which is more resistant to ozone [7].
mp,
C
content, %
1
2
3
4
5
6
7
8
9
90.2
89.6
89.3
91.0
90.1
89.9
89.0
89.3
90.4
90.1
78.0
92.9
93.0
93.1
92.9
93.1
92.9
93.0
93.2
93.1
242.0
99.2
99.4
99.1
99.3
99.2
99.3
99.3
99.1
99.4
99.3
241.5
241.0
241.5
242.5
242.0
241.5
242.5
242.0
241.5
10
*
Charged, M: 4-nitrotoluene 1.01, KBr 0.095 (in run no. 1,
0.126), Co(II) acetate or chloride 0.014 (in run no. 1, 0.023),
The amount of the catalyst lost in the cycle was
determined in the presence of acetic anhydride
(0.495 M). We found that, on adding potassium bro-
mide (0.063 M, 75%) and cobalt diacetate (0.012 M,
61.5%) to the recycling filtrate, the selectivity of 4-ni-
acetic anhydride 3.7 (in run no. 1, 0); in run no. 1, CH COOH
3
(40 ml); in run nos. 2 10, filtrate after filtering off 4-nitro-
benzoic acid (36.3 ml) containing cobalt(II) and bromine com-
pounds.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 74 No. 10 2001

USE OF OZONE FOR PREPARING 4-NITROBENZOIC ACID IN A CLOSED PROCESS CYCLE 1779
trotoluene oxidation fluctuates about 93%, i.e., the
amount of the added components corresponds to the
catalyst loss.
REFERENCES
1. Gray, T.C. and Geddes, I.C., J. Pharmacy Pharmacol.,
1954, vol. 6, no. 2, p. 89.
To check the possibility of multiple use of mother
liquors, we performed seven cycles, with ten runs in
each, with addition of the catalyst, to compensate for
its loss in the previous run, and acetic anhydride.
The yield of 4-nitrobenzoic acid in oxidation of 4-ni-
trotoluene in the mother liquor was obtained at a level
of 93% (see table).
2. Lisitsyn, V.N., Khimiya i tekhnologiya promezhutoch-
nykh produktov (Chemistry and Technology of Inter-
mediates), Moscow: Khimiya, 1987.
3. USSR Inventor’s Certificate, no. 421733.
4. JPN Patent 52-91837.
5. Galstyan, G.A., Matsegora, L.A., and Popova, I.A.,
Zh. Prikl. Khim., 1982, vol. 49, no. 1, pp. 138 142.
CONCLUSION
6. Galstyan, G.A., Galstyan, T.M., and Sokolova, S.M.,
Kinet. Katal., 1993, vol. 33, no. 4, pp. 779 787.
It is feasible to prepare 4-nitrobenzoic acid by
oxidation of 4-nitrotoluene in a closed process cycle
with multiple use of mother liquors.
7. Potapenko, E.V. and Galstyan, G.A., Zh. Prikl. Khim.,
2000, vol. 73, no. 7, pp. 1218 1220.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 74 No. 10 2001