7717-76-2Relevant articles and documents
Preparation method of 4, 4'-diphenyl ether tetracarboxylic dianhydride
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Paragraph 0027-0035, (2021/05/29)
The invention provides a preparation method of 4, 4'-diphenyl ether tetracarboxylic dianhydride, which comprises the following steps: S1, dissolving 4-nitrophthalic acid in a solvent, and heating for dehydration; S2, adding a molybdenum salt catalyst, a halogen promoter and carbonate into the reaction liquid obtained in S1, and carrying out etherification coupling reaction to obtain a 4, 4'-diphenyl ether tetracarboxylic acid crude product; S3, refining and dehydrating the crude product obtained in S3 to obtain 4, 4'-diphenyl ether tetracarboxylic dianhydride; wherein the weight ratio of the 4-nitrophthalic acid to the solvent to the molybdenum salt to the halogen is 1: (2-3.5): (0.02-0.05): (0.1-0.3); and the molar ratio of the 4-nitrophthalic acid to the carbonate is 1: (0.55-0.75). The molybdenum powder serves as the catalyst, the halogen serves as the cocatalyst, the conversion rate of the 4-nitrophthalic acid is larger than 99%, the molar yield of the 4, 4'-diphenyl ether tetracarboxylic acid crude product is larger than 85%, the method is unique, the technological process is simple, operation is easy, the yield is high, the cost is low, and the production efficiency and economic benefits are high.
Method of Purifying Dianhydrides, the Dianhydrides Formed Thereby, and Polyetherimides Formed Therefrom
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Page/Page column 14, (2009/10/06)
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.
Method of purifying dianhydrides
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Page/Page column 13, (2008/06/13)
Disclosed herein is a method for purification of dianhydrides comprising a substantial amount (10000 ppm or more) of at least one metal salt. In one aspect the method is useful for the purification of dianhydrides prepared by the reaction of a halophthalic anhydride with a metal carbonate and may be optionally catalyzed by a phase transfer catalyst. The purification of the dianhydrides may be accomplished by hydrolyzing the dianhydride metal salt mixture directly to a tetraacid with an inorganic acid, followed by separating the impurities from an aqueous phase, and subsequently heating the tetraacid to effect ring closure to form a purified dianhydride having less than 50 parts per million metal halide and lower levels of other residual impurities. In one aspect the method is highly effective in removing phase transfer catalyst impurities such as hexalkylguanidinium halides initially present in the dianhydride undergoing purification.
