urbaf2

TNT MANUFACTURE 365

The following nitric acid balance for the nitration of over 800 tons of toluene

is given below (according to British data of 1914-1918). The balance takes into

account both the quantity of nitric acid introduced into TNT in the form of nitro

groups and that lost in various ways:

nitric acid used for the formation of NO 2 groups

oxidation losses in the form of “fumes”and in wash waters from trinitration

losses in mononitration (“fumes”, washing out with water)

losses at denitration

losses in the nitric acid plants

Total

CONTINUOUS METHODS OF NITRATION

79.64%

11.22%

1.08%

1.75%

6.31%

100.00%

Earlier methods................................

Although various descriptions of the continuous nitration of aromatic hydro-

carbons have been known for a long time (e.g. patents granted to the companies:

Meister, Lucius and Brüning in Höchst [9]; Weiler-ter-Meer in Uerdingen [10];

Westphalisch-Anhaltische Sprengstoffe A. G. [11] and a well-known patent granted

to Kubierschky [12]), until recently these methods were not widely used. Partic-

ularly in the explosives industry, conservatism and fear of the adoption of any

new untraditional methods not known to be safe, have been strong enough to

prevent their realization. Hence most of the proposed methods have not been

put into practice.

Methods of continuous nitration of aromatic hydrocarbons may be based on

one of the following principles:

1. Nitration in the vapour phase. In methods of this kind (e.g. the Wilhelm

method [13]) a continuous stream of vapours of the aromatic hydrocarbon and nitric

acid or nitrogen dioxide is introduced into the reactor. Sulphuric acid is not used

in this reaction.

One drawback of this method common to all processes taking place in the

gaseous phase, is the necessity of using very large units, much larger than the capacity

of the reactors for liquid processes. These methods have not found any practical
uses.

2. Partial pressures method. Othmer and his co-workers [14-16] have suggested

amethod in which a mixture of hydrocarbon and nitric acid of about 61% con-

centration is boiled. The water liberated in the reaction is distilled off with part

of hydrocarbon, as an azeotrope. The two components are separated in a receiver

into two layers, the water being drained off and the hydrocarbon recycled. AS

a result of the reaction mono- and di-nitro derivatives can be obtained. The method

has been developed on the laboratory scale only.

3. Counter-current method. The method was suggested by Kubierschky [12].

The nitrator for nitrating benzene to nitrobenzene takes the form of a column.
A mixture of nitric and sulphuric acids is introduced at the top while a mist of

hydrocarbon is fed in at the bottom. The middle part of the column plays the role