Patent ID: 8492565

Claim:
A process for producing biphenyltetracarboxylic acid dianhydride, which comprises heating biphenyltetracarboxylic acid to produce biphenyltetracarboxylic acid dianhydride, characterized in that the heating is carried out by means of a heating device which houses a hollow rotary shaft provided with a plurality of hollow rotary heating members and which is designed to feed a heated heating medium to hollow portions of the rotary heating members via a hollow portion of the rotary shaft, and also to a heating jacket provided as the case requires, thereby to supply an amount of heat required for the reaction by heat transfer from each surface of such a rotary shaft, rotary heating members, and, if required, a heating jacket, wherein each of the hollow rotary heating members has a wedge shape as viewed from the side and a fan shape as viewed from the front and is secured at the neck portion of the fan shape to the hollow rotary shaft, and yet, from one end of the heating device, a biphenyltetracarboxylic acid powder as a starting material is continuously supplied, and the powder is heated as it is contacted with the hollow rotary heating members which are rotating and is subjected to a dehydration reaction while it is transferred in an axial direction in the heating device, and biphenyltetracarboxylic acid dianhydride as a product is continuously discharged from the other end of the heating device.