Paradichlorobenzene is manufactured through the fluid phase chlorination of benzene with chlorine in the presence of a catalyst such as ferric chloride. This process produces paradichlorobenzene along with other byproducts, so purification is needed through distillation and fractional crystallization. While some paradichlorobenzene plants have closed due to low profits, leading producers like Lanxess have increased capacity by modifying existing facilities and shifting production to focus more on paradichlorobenzene.

1. Paradichlorobenzene is a
fumigant insecticide used to
combat moths in clothing.
It can also be used in deodorant
blocks made for toilets and trash
cans.
Paradichlorobenzene was first
licensed in the United States for
use in 1942, and is often referred
to as
1,4-dichlorobenzene.

3. The manufacture of p-DCB is accomplished by the
fluid phase chlorination of benzene in the presence of
a catalyst, usually ferric chloride, aluminium chloride
or stannous tetrachloride, at atmospheric pressure
between 20 to 80o
C (Beck, 1986).
• By adjusting the temperature of the process and
the molar ratio of benzene to chlorine, the
percentage of final chlorinated products can be
determined.
• The process typically yields a mixture of
chlorobenzene, isomers of dichlorobenzene and
small quantities of higher chlorinated benzenes.
Subsequent purification is achieved by distillation
and fractional crystallization.
• The resulting p-DCB contains less than 0.5% each
of 1,2- and 1,3-dichlorobenzene and less than 0.1%
monochlorobenzene and trichlorobenzene.

4. The formation of paradichlorobenzene
is accompanied by the formation of
various by-products such as ortho-
dichlorobenzene, meta-
dichlorobenzene, morehighly
chlorinated benzenes, and often some
degradation products.
Here is an example of benzene being
added and using ferric chloride as a
catalyst to produce PDB:
C6H6 + 2 Cl2 → C6H4Cl2 + 2 HCl

5. para-dichlorobenzene cannot be
produced alone. When manufactured by
reacting chlorine with benzene, other
mono-, di-, and tri-chlorinated benzene
by-products are produced. To assure
economic viability, a plant producing
para-dichlorobenzene needs to
maximize para-dichlorobenzene
selectivity, while also finding
acceptable commercial outlets for by-
products, establishing an economically
viable slate of production.

6. Top Leading Players in Para-
Dichlorobenzene are ABI Chemicals, AK
Scientific, Alfa Aesar, Angene, Apollo
Scientific, Conier, GFS Chemicals,
Finetech Industry, Hangzhou Uniwise
International

7. Despite the permanent shutdown of
many chlorinated solvent plants in
industrialized countries due to reduced
demand and low profitability, some
industry leaders have found economical
ways to modify existing plants and shift
product slates. For example, the leading
producer in Western Europe, Lanxess,
continues to increase its capacity to
produce para-dichlorobenzene.
Lanxess recently added an additional
crystallizer, increasing capacity for
para-dichlorobenzene production

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