Phthalic Anhydrie

Phthalic Anhydride Was First Reported In 1836 By Auguste Laurent. More Contemporary[Clarification Needed] Routes Include Oxidation Of Naphthalene Or Ortho-Xylene. Vanadium Pentoxide (V2O5) Is The Active Oxidant For Several Key Steps Of The Processes, And Is Regenerated By Molecular Oxygen.

Starting From O-Xylene, The Oxidation Reaction Is Run At About 320–400 °C And Has The Following Stoichiometry:

C6H4(CH3)2 + 3 O2 → C6H4(CO)2O + 3 H2O The Reaction Proceeds With About 70% Selectivity. About 10% Of Maleic Anhydrous Is Also Produced:

C6H4(CH3)2 + 7.5 O2 → C4H2O3 +4 H2O + 4 CO2 Phthalic Anhydride And Maleic Anhydride Are Recovered By Distillation By A Series Of Switch Condensers.

The Naphthalene Route (The Gibbs Phthalic Anhydrous Process Or The Gibbs–Wohg Naphthalene Oxidation Reaction), A Process Whose Use Has Declined In Compared To The O-Xylene Route, Has The Following Mechanism:

Phthalic Anhydride Can Also Be Prepared From Phthalic Acid By Simple Dehydration