Abstract: A method for producing an aromatic dianhydride includes reacting an aromatic diimide with a substituted or unsubstituted phthalic anhydride in an aqueous medium in the presence of an amine exchange catalyst to provide an aqueous reaction mixture including an N-substituted phthalimide, an aromatic tetraacid salt, and at least one of an aromatic triacid salt and an aromatic imide diacid salt. The method further includes removing the phthalimide from the aqueous reaction mixture by extracting the aqueous reaction mixture with an organic solvent using a single packed extraction column. The aromatic tetraacid salt is converted to the corresponding aromatic dianhydride. Aromatic dianhydrides prepared according to the method are also described.

Abstract: A method for producing an aromatic dianhydride includes reacting an aromatic diimide with a substituted or unsubstituted phthalic anhydride in an aqueous medium in the presence of an amine exchange catalyst to provide an aqueous reaction mixture including an N-substituted phthalimide, an aromatic tetraacid salt, and at least one of an aromatic triacid salt and an aromatic imide diacid salt. The method further includes removing the phthalimide from the aqueous reaction mixture by extracting the aqueous reaction mixture with an organic solvent in a first extractor for a first time period, at a first extraction temperature and subsequent to the first time period, extracting the aqueous reaction mixture with an organic solvent in a second extractor for a second time period, at a second extraction temperature. The aromatic tetraacid salt is converted to the corresponding aromatic dianhydride. Aromatic dianhydrides prepared according to the method are also described.

Abstract: A method for producing an aromatic dianhydride includes reacting an aromatic diimide with a substituted or unsubstituted phthalic anhydride in an aqueous medium in the presence of an amine exchange catalyst to provide an aqueous reaction mixture including an N-substituted phthalimide, an aromatic tetraacid salt, and at least one of an aromatic triacid salt and an aromatic imide diacid salt. The method further includes removing the phthalimide from the aqueous reaction mixture by extracting the aqueous reaction mixture with an organic solvent using a sieve tray extraction column. The aromatic tetraacid salt is converted to the corresponding aromatic dianhydride. Aromatic dianhydrides prepared according to the method are also described.

Abstract: A method for producing an aromatic dianhydride includes reacting an aromatic diimide with a substituted or unsubstituted phthalic anhydride in an aqueous medium in the presence of an amine exchange catalyst to provide an aqueous reaction mixture including an N-substituted phthalimide, an aromatic tetraacid salt, and at least one of an aromatic triacid salt and an aromatic imide diacid salt. The method further includes removing the phthalimide from the aqueous reaction mixture by extracting the aqueous reaction mixture with an organic solvent using a sieve tray extraction column. The aromatic tetraacid salt is converted to the corresponding aromatic dianhydride. Aromatic dianhydrides prepared according to the method are also described.

Abstract: A method for producing an aromatic dianhydride includes reacting an aromatic diimide with a substituted or unsubstituted phthalic anhydride in an aqueous medium in the presence of an amine exchange catalyst to provide an aqueous reaction mixture including an N-substituted phthalimide, an aromatic tetraacid salt, and at least one of an aromatic triacid salt and an aromatic imide diacid salt. The method further includes removing the phthalimide from the aqueous reaction mixture by extracting the aqueous reaction mixture with an organic solvent in a first extractor for a first time period, at a first extraction temperature and subsequent to the first time period, extracting the aqueous reaction mixture with an organic solvent in a second extractor for a second time period, at a second extraction temperature. The aromatic tetraacid salt is converted to the corresponding aromatic dianhydride. Aromatic dianhydrides prepared according to the method are also described.

Abstract: A method for producing an aromatic dianhydride includes reacting an aromatic diimide with a substituted or unsubstituted phthalic anhydride in an aqueous medium in the presence of an amine exchange catalyst to provide an aqueous reaction mixture including an N-substituted phthalimide, an aromatic tetraacid salt, and at least one of an aromatic triacid salt and an aromatic imide diacid salt. The method further includes removing the phthalimide from the aqueous reaction mixture by extracting the aqueous reaction mixture with an organic solvent using a single packed extraction column. The aromatic tetraacid salt is converted to the corresponding aromatic dianhydride. Aromatic dianhydrides prepared according to the method are also described.

Abstract: A method for the purification of a 2-aryl-3,3-bis(hydroxyaryl)phthalimidine of formula (I), the method comprising heating a reaction mixture comprising a phenolphthalein compound of formula (II) and a primary arylamine of formula (III) in the presence of an acid catalyst to form a reaction mixture; removing water from the reaction mixture; quenching the reaction mixture with an aqueous alkali solution to form a quenched reaction mixture; extracting the quenched reaction mixture with an aminoaryl compound of formula (IV) to form an organic layer and an extracted aqueous layer comprising a crude 2-aryl-3,3-bis(hydroxyaryl)phthalimidine compound; contacting the extracted aqueous layer with carbon to form a semi-purified 2-aryl-3,3-bis(hydroxyaryl)phthalimidine compound; and mixing the semi-purified 2-aryl-3,3-bis(hydroxyaryl)phthalimidine compound with a solution comprising an alcohol and an acid to form a purified 2-aryl-3,3-bis(hydroxyaryl)phthalimidine of formula (I); wherein formulas (I), (II), (III), and (I

Abstract: Systems and methods of monitoring a power system power converter are provided herein. The system includes a plurality of parallel-coupled power converters comprising a power converter input and a power converter output, the power converter output configured to be coupled to a load, each power converter of the plurality of parallel-coupled power converters comprising a power converter controller. The power converter controller is configured to compare an output current of a corresponding power converter to a predetermined output current threshold, monitor the output current for a predetermined time duration when the output current is below the predetermined output current threshold, and shut down the corresponding power converter when the output current is below the predetermined output current threshold for the predetermined time duration.

Abstract: Systems and methods of monitoring a power system power converter are provided herein. The system includes a plurality of parallel-coupled power converters comprising a power converter input and a power converter output, the power converter output configured to be coupled to a load, each power converter of the plurality of parallel-coupled power converters comprising a power converter controller. The power converter controller is configured to compare an output current of a corresponding power converter to a predetermined output current threshold, monitor the output current for a predetermined time duration when the output current is below the predetermined output current threshold, and shut down the corresponding power converter when the output current is below the predetermined output current threshold for the predetermined time duration.