Armstrong, Westermen, Hattori, McLeland & Naughton
Process for producing pyromellitic dianhydride
 Pyromellitic dianhydride, useful as raw material for the manufacture of polyimides, is prepared in high yield and purity by the reaction of benzene derivatives such as ethylbenzene, diethylbenzenes, and triethylbenzenes with an ethylating agent in the presence of a Friedel-Crafts catalyst, the separation of tetraethylbenzenes from the reaction products by distillation, the separation of 1,2,4,5-tetraethylbenzene from other tetraethyl benzenes by differential centrifugal precipitation at -10 to -30 degrees Celsius, and the catalytic vapor-phase oxidation of tetraethyl benzenes, using a catalyst containing vanadium pentoxide and titanium dioxide. 
Nippon Steel Chemical Co., Ltd.
C
C07C
inventional
Noboru Tadanori Kunio Masakazu
Daito Hara Wada Takeuchi