Phthalic anhydride is one of the most important products of modem large-scale organic synthesis, and it has a wide application in various branches of chemical industry. It is mostly used (60% of the world production) for preparation plasticizers for PVC. The rapid development of the industrial production of polymeric materials during the last two decades increased the need of phthalic anhydride, which resulted in an increase of its production [1, 2].