Phthalic Anhydride (98,5%) - Thailand

Description:
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 used commercially. This white solid is an important industrial chemical, especially for the large-scale production of plasticizers for plastics. In 2000, the worldwide production volume was estimated to be about 3 million tonnes per year.
Manufacturing Process:
Phthalic anhydride was first reported in 1836 by Auguste Laurent. More contemporary 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 anhydride 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 anhydride 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.