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History of phthalic anhydride:

Auguste Laurent first reported phthalic anhydride in 1836. More contemporary

routes include catalytic oxidation of ortho-xylene and naphthalene ("Gibbs phthalic

anhydride process"), although use of naphthalene has declined. Starting from o-

xylene, the oxidation follows the following stoichiometry:

C6H4(CH3)2 + 3 O2 C6H4(CO)2O +3 H2O

Phthalic anhydride is the organic compound with the formula C6H4(CO)2O. It is

the anhydride of phthalic acid. Phthalic anhydride is a principal commercial form

of phthalic acid. It was the first anhydride of a dicarboxylic acid to be usedcommercially. This colorless solid is an important industrial chemical, especially

for the large-scale production of plasticizers for plastics. In 2000, the world wide

production volume was estimated to be about 3M tones per year.

A modified vanadium pentoxide (V2O5) serves as the catalysts, being active in the

range 320 - 400 C. The phthalic anhydride is separated from byproducts by a a

series of switch condensers. Phthalic anhydride and maleic anhydride are

recovered by distillation. Phthalic anhydride can also be prepared from

phthalicacid

Uses:The primary use of Phthalic Anhydride is as a chemical intermediate in the

production of plastics from vinyl chloride. Phthalate esters, which function as

plasticizers, are derived from Phthalic Anhydride. Phthalate plasticizers are usedfor the production of flexible PVC products such as cables, pipes and hoses, leather

cloth, shoes, film for packaging etc. Phthalic Anhydride has another major use in

the production of polyester resins and other minor uses in the production of alkyd

resins used in paints and lacquers; certain dyes (anthraquinone, phthalein,

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rhodamine, phthalocyanine, fluorescin, and xanthene dyes); insect repellents; and

polyester polyols for polyurethanes. Besides, it is also utilized as a rubber scorch

inhibitor and retarder