Method for increasing the yield of 2,6 -NDA

This invention is related to the production of 2,6-naphthalene dicarboxylic acid (2,6-NDA). More particularly, this invention is related to a reaction step known in the art for the purification of 2,6-NDA in which the monosalt of 2,6-NDA, KHNDA, is heated in water or aqueous solvent to cause the disproportionation thereof, and to the stoichiometric limitation of the reaction to produce 50% 2,6-NDA on a molar basis. The present invention is a method for increasing the yield at least about 20% or more beyond the stoichiometric limitations. Disclosed is a method of increasing the yield of 2,6-NDA which comprises:a) Dissolving a disproportionation reaction product containing a dialkali salt of 2,6-NDA in water and filtering off insoluble matter from the resulting solution;b) Precipitating the monoalkali salt of 2,6-NDA (KHNDA) with CO;c) Suspending said monoalkali salt in water in a weight ratio higher than 8:1, water: monosalt; andd) Heating at a temperature above 100° C. and at a pressure above 100 psig.The improvements in yield are from about 20% to as high as 45%.