To provide a method for inexpensively producing less discolored pyromellitic dianhydride with low contents of monoanhydrides of aromatic dicarboxylic acids or aromatic tricarboxylic acids or monoanhydrides such as pyromellitic monoanhydride, etc., and having particle properties of causing no clogging of reactors, transfer containers, pipes, etc.
The method for producing pyromellitic dianhydride comprises a step of thermally dehydrating crude pyromellitic acid in the absence of acetic anhydride, converting 50.0-99.5 wt.% of pyromellitic acid into pyromellitic dianhydride and affording a reaction mixture containing at least pyromellitic acid and pyromellitic dianhydride and a step of thermally dehydrating the reaction mixture in the presence of acetic anhydride.
OGOSHI ATSUSHI
YABUNO MASASHI
INARI MASAHITO
Masamichi Tohei