Mitsubishi Gas Chemical Company, Inc.

Tsuneo Kosaka

Yukio Sakai

A process for preparing pyromellitic dianhydride by dehydration of pyromellitic acid is disclosed. The dehydration is conducted in solid state by indirect heating. The characteristic feature of the process is that when the most part of pyromellitic acid was converted to the dianhydride, the remaining pyromellitic acid is dehydrated while regulating the temperature of the heating medium between 200.degree. C. and 235.degree. C. By this process, pyromellitic dianhydride with excellent quality, good color and free flowing property can be obtained easily, smoothly, and rapidly. A very simple apparatus can be used in the process and the apparatus can be constructed from cheap materials.

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Kurashiki, Japan

Tsuneo Kosaka