Study On The Crystallization Purification Process Of Isophthalonitrile

Isophthalonitrile(IPN) is useful as a raw material for producing synthetic resins and agrochemicals and an important intermediate material for compounds such as amines and isocyanates,mainly in production of chlorothalonil and m-phenylenediamine.It is often produced via an ammoxidation involving meta-xylene,oxygen and ammonia over a catalyst.Because of existence of impurities which arise from ammoxidation by-products,the purity of IPN produced straightly by ammoxidation can not satisfy the requirements of the world markets.Thus,the object of this paper is to provide a method for producing high-purity IPN in an industrially advantageous manner.This paper study on the process of purifying isophthalonitrile via crystallization.First,the solubility of isophthalonitrile in some solvents was measured and the purity of crystal products from these solvents was determined by liquid chromatography,and finally ethanol-water was selected as crystallization solvents.Second, the metastable zone of IPN in ethanol-water was measured by using laser method, and the calculate formulas of solubility and supersolubility of IPN were obtained through the experimental data regression, which provide basic data for the study on crystallization process.Third, this paper provided a method of fast cooling-down crystallization to avoid agglomeration phenomena which has some bad effect on the shape, size distribution and purity of the final products.A special and novel experimental device was designed and developed to research on the effects of fast cooling-down temperature and solvent mixture ratio through the analysis on the initial and final crystal size distribution.