Abstract: Disclosed is a method for purifying 2,6-naphthalenedicarboxylic acid (NDA) that is present in a solid state in a solution. According to the method, sintered metal membrane filtration units are used to efficiently separate and purify 2,6-naphthalenedicarboxylic acid separated after hydrogenation and crystallization in a continuous process. An apparatus for implementing the method is further provided.

Abstract: Provided is a method for the separation and purification of high-purity 2,6-dimethylnaphthalene from a reaction mixture of dimethylnaphthalenes by continuous crystallization. According to the method, shell-tubetype crystallization apparatuses are used to perform crystallization operations under a continuous flow of a reaction mixture of dimethylnaphthalenes, which is obtained from the synthesis of dimethylnaphthalenes using o-xylene and butadiene as starting materials. As a result, high-purity 2,6-dimethylnaphthalene is separated and purified in a high yield from the reaction mixture. In addition, the method is advantageous in terms of energy saving when compared to conventional separation methods and enables continuous separation and purification of 2,6-dimethylnaphthalene on an industrial scale. A system for implementing the method is further provided.