Abstract: A method for purifying an oxydiphthalic anhydride comprises diluting a first mixture comprising an oxydiphthalic anhydride, a solvent, a catalyst, and an inorganic salt with a solvent, to provide a second mixture having a solids content of 10 to 30 percent based on total weight of the second mixture; filtering and washing the solids of the second mixture at a temperature below the crystallization point temperature of the oxydiphthalic anhydride to provide a third mixture; hydrolyzing the third mixture by adding water and a water-soluble acid to form a fourth mixture; heating the fourth mixture; then cooling to provide a solid-liquid mixture, optionally decanting a portion of the liquid, rediluting the remaining solid-liquid mixture, then filtering to provide a solid component; washing the solid component with water to provide a fifth mixture of oxydiphthalic tetraacid and water; ring closing the oxydiphthalic tetraacid to provide oxydiphthalic anhydride, and filtering the oxydiphthalic anhydride.

Abstract: A method for preparing an oxydiphthalic anhydride comprises contacting, under reactive and substantially anhydrous conditions in a reactor, at least one halophthalic anhydride containing more than 250 ppm chlorophthalide impurity with a carbonate of the formula M2CO3, wherein M is an alkali metal, in the presence of a catalytic proportion of at least one phase transfer catalyst selected from the group consisting of hexaalkylguanidinium halides and alpha,omega-bis(pentaalkylguanidinium)alkane salts, phosphonium salts, phosphazenium salts, pyridinium salts, phosphazenium salts, ammonium salts, and combinations thereof. The phase transfer catalyst is present in a sufficient amount to prepare the oxydiphthalic anhydride when the chlorophthalide is present in an amount that is more than 250 ppm, and the oxydiphthalic anhydride is produced in a yield, based on the carbonate, of at least 70%.

Abstract: A method for purifying an oxydiphthalic anhydride comprises diluting a first mixture comprising an oxydiphthalic anhydride, a solvent, a catalyst, and an inorganic salt with a solvent, to provide a second mixture having a solids content of 10 to 30 percent based on total weight of the second mixture; filtering and washing the solids of the second mixture at a temperature below the crystallization point temperature of the oxydiphthalic anhydride to provide a third mixture; hydrolyzing the third mixture by adding water and a water-soluble acid to form a fourth mixture; heating the fourth mixture; then cooling to provide a solid-liquid mixture, optionally decanting a portion of the liquid, rediluting the remaining solid-liquid mixture, then filtering to provide a solid component; washing the solid component with water to provide a fifth mixture of oxydiphthalic tetraacid and water; ring closing the oxydiphthalic tetraacid to provide oxydiphthalic anhydride, and filtering the oxydiphthalic anhydride.

Abstract: a method for preparing an oxydiphthalic anhydride comprises contacting, under reactive and substantially anhydrous conditions in a reactor, at least one halophthalic anhydride containing more than 250 ppm chlorophthalide impurity with a carbonate of the formula M2CO3, wherein M is an alkali metal, in the presence of a catalytic proportion of at least one phase transfer catalyst selected from the group consisting of hexaalkylguanidinium halides and alpha,omega-bis(pentaalkylguanidinium)alkane salts, phosphonium salts, phosphazenium salts, pyridinium salts, phosphazenium salts, ammonium salts, and combinations thereof. The phase transfer catalyst is present in a sufficient amount to prepare the oxydiphthalic anhydride when the chlorophthalide is present in an amount that is more than 250 ppm, and the oxydiphthalic anhydride is produced in a yield, based on the carbonate, of at least 70%.