Vanadium phthalic anhydride synthesis

Heterogeneous oxidative processes operate at high temperatures (250-450 6C) and are useful for the synthesis of acrolein and acrylic acid from propylene over bismuth molybdate catalysts, the synthesis of maleic and phthalic anhydrides from the oxidation of benzene (or C4 compounds) and naphthalene (or o-xylene) respectively over vanadium oxide,101 arid the synthesis of ethylene oxide from ethylene over silver catalysts.102... 

A process akin to the allylic oxidation in activation is aromatic side chain oxidation to produce acids or anhydrides. Phthalic anhydride, an important intermediate in production of polyesters, plasticizers, and fine chemicals synthesis, can be produced via selective oxidation of -xylenes using vanadium oxide catalysts (Eqn. 3). This process today accounts for over 85% of the phthalic anhydride produced worldwide, and has largely displaced the partially wasteful and more expensive naphthalene-based route (Eqn. 4), by which nearly all PA was produced in 1960 (Figure 4). Nearly all of the phthalic anhydride produced today is used for manufacturing vinyl plasticizers, with a much smaller application in the fine chemicals industry. 

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