Page 37 - Chemical and process design handbook

Speight_Part 1_H 11/7/01 3:03 PM Page 1.23

HALOGENATION 1.23
of by-product hydrogen chloride from other processes is frequently available
and the use of cuprous chloride (CuCl) and cupric chloride (CuCl ), along
2
with some potassium chloride (KCl) as a molten salt catalyst, enhances the
reaction progress.
Ethane can be chlorinated under conditions very similar to those for
methane to yield mixed chlorinated ethanes.
Chlorobenzene is used as a solvent and for the manufacture of
nitrochlorobenzenes. It is manufactured by passing dry chlorine through
benzene, using ferric chloride (FeCl ) as a catalyst:
3
C H + C1 → C H Cl + HCl
6 6 2 6 5
The reaction rates favor production of chlorobenzene over dichloroben-
o
zene by 8.5:1, provided that the temperature is maintained below 60 C.
The hydrogen chloride generated is washed free of chlorine with benzene,
then absorbed in water. Distillation separates the chlorobenzene, leaving
mixed isomers of dichlorobenzene.
In aqueous media, when hydrochloric acid is present in either the liquid
or vapor phase and particularly when under pressure, tantalum is undoubt-
edly the most resistant material of construction. Reactors and catalytic
tubes lined with this metal give satisfactory service for prolonged periods.