The Application Of Adductive Crystallization In The Separation And Purification Of Aromatic Carboxylic Acids

There are many components worth to be recycled in the purified terephthalic acid (PTA) oxidation residual, such as benzoic acid (BA), terephthalic acid (TA), isophthalic acid (IPA) and so on. However, the residual is usually treated with burning or burying method in the industry, which not only pollutes the environment but also wastes sources. In this paper, the adductive crystallization method was applied to the recycling of PTA oxidation residual innovatively. The effect of all the main components in the residual on the crystallization process was studied here. The result shows that the residual with BA removed can be treated with adductive crystallization method to separate TA and IPA. So the effective method to recycle BA in the residual was further researched. And the three-component solid-liquid phase equilibrium data among TA, IPA and DMAC at303.2K were determined and correlated with the thermodynamic model. All these work have demonstrated the feasibility of the recycling of the PTA oxidation residual with the adductive crystallization method and made the foundation for the future research.The crude2,6-naphthalenedicarboxylic acid (NDA) product always contains residual metal-catalysts and organic impurities formed during the oxidation process, which need to be further separated to get high purified NDA. However, the conventional separation methods can’t purify NDA effectively. In this paper, the adductive crystallization method was applied to this field. Here, the appropriate crystallization solvents were studied. The crystal structure and thermodynamic properties of the adducts were analyzed. And the related solid-liquid phase equilibrium data were determined and correlated, too. All these data are the foundation for the substantial work.