Studies on the Production of Pyromellitic Dianhydride (II)

Vapour pressure of durene oxidation products, pyromellitic dianhydride, 5-methyl trimellitic anhydride, 4, 5-dimethyl phthalic anhydride, 4, 6-dimethyl isophthalic acid, 2, 5-dimethyl terephthalic acid and durylic acid were measured.The rate of thermal dehydration reaction of pyromellitic acid to pyromellitic dianhydride was of zero order and the activation energy of this reaction was 20kcal/mol.Pure pyromellitic dianhydride was collected selectively when the gaseous products obtained by the vapour phase catalytic oxidation of durene was cooled in the collector which was controlled at the temperature of 175°C.The temperature of the collector affected the purity and the yield of pyromellitic dianhydride; as the temperature of collector rose, the purity of pyromellitic dianhydride was increased, but the yield was decreased. Under the assumption that the Raoult's Law was applicable to this system, the calculated purity and the yield of pyromellitic dianhydride in the collector were in good agreement with the experimental results.