Synthesis and Production
Phthalic anhydride was first reported in 1836 by Auguste Laurent. It is presently obtained by catalytic oxidation of ortho-xylene and naphthalene ("Gibbs phthalic anhydride process"):
- C6H4(CH3)2 + 3 O2 → C6H4(CO)2O + 3 H2O
- C10H8 + 4.5 O2 → C6H4(CO)2O + 2 H2O + 2 CO2
The catalyst that is used for the oxidation of xylene is a modified vanadium pentoxide (V2O5). When separating the phthalic anhydride from byproducts such as o-xylene in water, or maleic anhydride, a series of “switch condensers” is required. Phthalic anhydride can also be prepared from phthalic acid:
Read more about this topic: Phthalic Anhydride
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