Page 30 - Chemical and process design handbook

Speight_Part 1_E&F 11/7/01 3:03 PM Page 1.16

ESTERIFICATION

A variety of solvents, monomers, medicines, perfumes, and explosives are
made from esters of nitric acid. Ethyl acetate, n-butyl acetate, iso-butyl
acetate, glycerol trinitrate, pentaerythritol tetranitrate (PETN), glycol dini-
trate, and cellulose nitrate are examples of such reactions.
Ester manufacture is a relatively simple process in which the alcohol
and an acid are heated together in the presence of a sulfuric acid catalyst,
and the reaction is driven to completion by removing the products as
formed (usually by distillation) and employing an excess of one of the
reagents. In the case of ethyl acetate, esterification takes place in a column
that takes a ternary azeotrope. Alcohol can be added to the condensed over-
head liquid to wash out the alcohol, which is then purified by distillation
and returned to the column to react.
Amyl, butyl, and iso-propyl acetates are all made from acetic acid and
the appropriate alcohols. All are useful lacquer solvents and their slow rate
of evaporation (compared to acetone or ethyl acetate) prevents the surface of
the drying lacquer from falling below the dew point, which would cause con-
densation on the film and a mottled surface appearance (blushing). Other
esters of importance are used in perfumery and in plasticizers and include
methyl salicylate, methyl anthranilate, diethyl-phthalate, dibutyl-phthalate,
and di-2-ethylhexyl-phthalate.
Unsaturated vinyl esters for use in polymerization reactions are made by
the esterification of olefins. The most important ones are vinyl esters: vinyl
acetate, vinyl chloride, acrylonitrile, and vinyl fluoride. The addition reac-
tion may be carried out in either the liquid, vapor, or mixed phases,
depending on the properties of the acid. Care must be taken to reduce the
polymerization of the vinyl ester produced.
Esters of allyl alcohol, e.g., diallyl phthalate, are used as bifunctional
polymerization monomers and can be prepared by simple esterification of
phthalic anhydride with allyl alcohol. Several acrylic esters, such as ethyl
or methyl acrylates, are also widely used and can be made from acrylic
acid and the appropriate alcohol. The esters are more volatile than the cor-
responding acids.

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