Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2003-01-30
2003-12-30
Dentz, Bernard (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C549S232000, C549S236000, C549S248000, C549S250000, C562S416000
Reexamination Certificate
active
06670487
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is related to a method for removing impurities from products derived from oxidation of ortho-dialkylaromatic compounds. In one embodiment the present invention is related to a method for removing impurities from products derived from oxidation of ortho-dimethylbenzenes. In another particular embodiment the present invention is related to a method for removing impurities from products derived from oxidation of halogenated ortho-dialkylbenzenes, and particularly from oxidation of halogenated ortho-dimethylbenzenes.
Aromatic ortho-dicarboxylic acids and their corresponding anhydrides are often produced by oxidation of ortho-dialkylaromatic compounds. A particular example is the well-known process for producing phthalic acid and phthalic anhydride by oxidation of ortho-xylene in the presence of a catalyst and oxygen source. Efficient processes for the production of halophthalic acid and halophthalic anhydride, such as chlorophthalic acid and chlorophthalic anhydride, via liquid-phase oxidation of halo-o-xylene using catalysts and an oxygen source have been recently described, for example in copending, commonly owned application Ser. No. 09/718,124, filed Nov. 20, 2000. In the preparation of chlorophthalic acid and chlorophthalic anhydride via liquid-phase oxidation, high first-pass yields are very important because intermediate products are difficult and expensive to separate from the product. When a mixture of 3-chloro-o-xylene and 4-chloro-o-xylene serves as starting material for the oxidation, the major impurities may comprise any of four chlorophthalides, or four chloro-toluic acids which may result from incomplete oxidation of the substrate. In the case of over oxidation one may obtain isomers of chlorobenzoic acid from decarboxylation or phthalic acid from dechlorination of the product, chlorophthalic acid. A problem is that neither conventional distillation nor recrystallization allows for a clean separation of the anhydrides from the phthalide or carboxylic acid impurities.
Elimination of impurities from oxidation product mixtures of ortho-dialkylaromatic compounds has in the past often relied on improving the oxidation process conditions to prevent impurity formation U.S. Pat. No. 4,436,922 teaches a process for conversion of impurities to desired products in a reoxidation process. Post-oxidation removal of impurities has been described in U.S. Pat. No. 4,165,324 wherein residual phthalide impurity is removed by treatment of an oxidation reaction mixture with alkali metal salts at high temperature. These approaches are deficient in that there is loss in yield, increase in color and increase in cost associated with the energy required to effect the reaction.
Extractions of liquid phase oxidation reaction mixtures have been described as a way to remove the metal catalyst components. Such extractions are usually done while the product is primarily insoluble in the aqueous phase as taught in U.S. Pat. No. 5,449,820. U.S. Pat. No. 5,770,764 utilizes aqueous solubility by employing trialkylamines to make the corresponding salts of oxidation products, followed by purifying the salts and recovering the acids.
Accordingly, there remains a need for an inexpensive and efficient method for removing organic impurities from products derived from oxidation of ortho-dialkylaromatic compounds. In particular, there is a need for a method for removing organic impurities from oxidation products comprising halophthalic acids and/or halophthalic anhydrides.
SUMMARY OF THE INVENTION
The present inventors have discovered a method for removing impurities from products derived from oxidation of an ortho-dialkylaromatic compound which comprises at least one step selected from the group consisting of extraction of an aqueous solution comprising aromatic dicarboxylic acid product with an organic solvent and extraction of an organic solution comprising aromatic anhydride product with an aqueous bicarbonate solution for a time period insufficient to allow hydrolysis of anhydride to acid.
Various other features, aspects, and advantages of the present invention will become more apparent with reference to the following description and appended claims.
DETAILED DESCRIPTION
In various embodiments products derived from oxidation of ortho-dialkylaromatic compounds comprise those derived from oxidation of substituted or unsubstituted xylene, or substituted or unsubstituted dimethylnaphthalene. Typical substituents, when present, on xylene or dimethylnaphthalene comprise alkyl or halo substituents. In some embodiments said products are those derived from oxidation of monohalo-ortho-xylene, in one particular embodiment from oxidation of 4-halo-ortho-xylene, and in other particular embodiments from oxidation of 4-fluoro- or 4-chloro-ortho-xylene. In another embodiment products are derived from oxidation of a mixture comprising 4-halo- and 3-halo-ortho-xylene, in some particular embodiments a mixture of 4-fluoro- and 3-fluoro-ortho-xylene and in other particular embodiments a mixture of 4-chloro- and 3-chloro-ortho-xylene. When 3-halo-ortho-xylene is present in a substrate for oxidation, it comprises in some embodiments about 0.001-35 molar percent, in other embodiments about 0.001-15 molar percent, in other embodiments about 0.01-12 molar percent, and in still other embodiments about 0.1-10 molar percent of total substrate.
In yet another embodiment products derived from oxidation of ortho-dialkylaromatic compounds comprise those derived from oxidation of at least one halo-ortho-xylene as described above, optionally in the presence of at least one halotoluic acid, in one embodiment at least one chlorotoluic acid (also known as chloro methylbenzoic acid), in another embodiment either (a) 4-chloro-2-methyl benzoic acid or (b) 5-chloro-2-methylbenzoic acid or (c) a mixture thereof, and in still another embodiment a mixture of either or both of (a) and (b) with either (d) 4-halo-ortho-xylene, or (e) a mixture of 4-halo- and 3-halo-ortho-xylene.
In still another embodiment products derived from oxidation of ortho-dialkylaromatic compounds comprise those derived from oxidation of a mixture of ortho-xylene with halo-ortho-xylene, in one embodiment either with (d) 4-halo-ortho-xylene, or with (e) a mixture of 4-halo- and 3-halo-ortho-xylene, or with at least one halotoluic acid, such as chlorotoluic acid, or with a mixture of halotoluic acid with either (d) 4-halo-ortho-xylene, or (e) a mixture of 4-halo- and 3-halo-ortho-xylene. When ortho-xylene is present in a substrate for oxidation, it typically comprises in one embodiment about 0.001-100 molar percent, in another embodiment about 0.001-10 molar percent and in still another embodiment about 0.01-1 molar percent of total substrate. In a particular embodiment products derived from oxidation of ortho-dialkylaromatic compounds comprise those derived from oxidation of 4-chloro-ortho-xylene, optionally in combination with at least one of 3-chloro-ortho-xylene, ortho-xylene, or chlorotoluic acid.
In various embodiments ortho-dialkylaromatic oxidation products comprise those obtained by oxidation of at least one of and sometimes both the two aromatic ortho-alkyl groups. In some embodiments ortho-dialkylaromatic oxidation products comprise those obtained by oxidation of at least one of and sometimes both of two aromatic ortho-methyl groups. In various embodiments the oxidation products comprise at least one of a substituted or unsubstituted aromatic ortho-dicarboxylic acid, or a substituted or unsubstituted aromatic anhydride derived from the corresponding aromatic ortho-dicarboxylic acid. In some particular embodiments the oxidation products comprise at least one of phthalic acid, phthalic anhydride, halotoluic acid, halophthalic acid, halophthalic anhydride, or mixtures thereof. In still other particular embodiments the oxidation products comprise at least one of phthalic acid, phthalic anhydride, chlorotoluic acid, 3-chlorophthalic acid, 3-chlorophthalic anhydride, 4chlorophthalic acid, 4-chlorophthalic anhydride, or mixt
Colborn Robert Edgar
Khouri Farid Fouad
Caruso Andrew J.
Dentz Bernard
General Electric Company
Patnode Patrick K.
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