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456 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

Other impurities which may be present in chlorodinitrobenzene are: chloro-

nitrobenezenes, as products of an incomplete nitration, m- dinitrobenzene formed

from benzene present in the chlorobenzene and chloropicrin.

MANUFACTURE OF o- AND p- CHLORONITROBENZENES

I. G. Griesheim method

At the Griesheim Works the following process was applied for nitrating chloro-

benzene to o- and p- chlorodinitrobenzenes. A cast iron nitrator is charged with

6530 kg of a nitrating mixture of the composition:

HNO 3 30%:

H 2 SO 4 56%

H 2 O 14%

Then 3500 kg of chlorobenzene from the extraction stage of the process (as

described below) is gradually run into the nitrator, with continuous stirring. The

chlorobenzene should be of high purity, boiling at 132°C and distilling within

a range of 0.5°. Initially a temperature of 40°C should be maintained and allowed

to rise to 55°C by the end of the operation. The nitrator contents are then heated

to 70-80°C during a period of 2 hr prior to transfer to a separator lined with acid

resistant ceramic tiles. After the mixture has settled, the lower acid layer is drawn

off to a special tank where it is stirred together with the chlorobenzene to be used

for the next nitration. In this way part of the chloronitrobenzene dissolved in the

acid, along with the remainder of nitric acid and nitrogen oxides, is extracted by the

chlorobenzene.

The oily upper layer of chloronitrobenzene is washed with water, then with

a sodium carbonate solution, and again with water, followed by drying under

reduced pressure. Drying of the product is necessary to prevent corrosion of the

crystallizers. In this way, 4850 kg of crude chloronitrobenzene (m, p. 52°C) are

obtained, a yield equivalent to 98% of the theoretical.

I. G. Leverkusen method

4500 kg of chlorobenzene is charged into 2500 kg of waste acid from the previous

batch in a nitrator of 10 m^3 capacity. Then 7100 kg of mixed acid containing:

HNO 3 35%

H 2 SO 4 52.5%

H 2 O 12.5%

is added with stirring and cooling, so that the temperature gradually rises in 9 hr
from 20°C to 50°C. The contents are then stirred for 3 hr at 80°C.
A sample is taken to test the washed and dried product (m. p. min. 53°C). The
spent acid should possess a density of 1.620 at 15°C; a content of HNO 3 less than
0.4% and of HNO 2 less than 0.4%. Usually the figures are 0.0% and 0.2% re-

spectively.