METHOD FOR PRODUCING TRANS-1,4-CYCLOHEXANE DICARBOXYLIC ACID

摘要

(1) A method for producing trans−1,4−cyclohexane dicarboxylic acid (t−CHDA), which comprises heating a crude CHDA to a temperature of 180°C or higher and retaining the temperature thereof in a region of 180°C or higher and less than the melting point of t−CHDA, to precipitate t−CHDA formed by isomerization in a molten cis−1,4−cyclohexane dicarboxylic acid (c−CHDA); (2) a method for producing t−CHDA, which comprises subjecting a crude CHDA in a powdery grain form to a heat treatment at a temperature of not lower than the melting point of c−CHDA and lower than the melting point of t−CHDA, to isomerize CHDA from its cis form to trans form while retaining a powdery grain form; (3) a method for producing t−CHDA, which comprises retaining the temperature of a crude CHDA in a region of not lower than the melting point of c−CHDA and lower than the melting point of t−CHDA, while allowing the crude CHDA to flow, to prepare a t−CHDA in a powdery grain form; (4) a method for purifying a crude CHDA which comprises heating a crude CHDA prepared by a process comprising hydrogenating TPA or the like in an inert gas atmosphere, to remove impurities through vaporization. The above methods allow the isomerization of c−CHDA for the production of a high purity t−CHDA to be carried out with good efficiency by the use of a simple and easy procedure.