Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2002-03-22
2003-12-02
Shah, Mukund J. (Department: 1624)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C562S416000, C549S246000
Reexamination Certificate
active
06657067
ABSTRACT:
BACKGROUND OF INVENTION
This invention relates to liquid phase oxidation of halogen substituted alkyl aromatic compounds. In particular,.the invention relates to liquid phase oxidation of chloro-ortho-xylene to produce chlorophthalic acid which can be dehydrated to produce chlorophthalic anhydride.
Liquid phase oxidation has long been used to produce dicarboxylic acids from dialkyl benzenes. Of particular interest has been the oxidation of dimethyl benzene (xylene) to phthalic acid, especially the oxidation of para-xylene to terephthalic acid, which is used in the production of polybutylene terephthalate. The liquid phase oxidation of xylene to phthalic acid requires the use of a catalyst, typically a cobalt/manganese/bromide catalyst system, and is generally performed in a carboxylic acid solvent such as acetic acid. The catalyst system may be augmented by the use of a co-catalyst such as zirconium, hafnium or cerium. Phthalic acid is an easily isolable solid, which can be filtered out of the reaction mixture.
Liquid phase oxidation, using a cobalt/manganese/bromide catalyst system and a carboxylic acid solvent, has also been applied to halogenated xylene with some success. The oxidation of the halogenated xylene is more difficult than the oxidation of xylene due to presence of a halogen, which is an electron withdrawing substituent, on the benzene ring. The greater difficulty in oxidation results in a lower reaction selectivity and a larger amount of partial oxidation and side products than seen in the liquid phase oxidation of xylene under similar conditions. Additionally, halogenated phthalic acid is difficult to separate from the partial oxidation and side products, even by distillation. Thus it is clear that in order for a method of halogenated xylene liquid phase oxidation to be commercially successful the reaction yield and the reaction selectivity must be very high. Optimally, for a useful commercial process, the reaction selectivity should be high enough to result in only negligible amounts of partial oxidation and side products thus removing the need for isolation of halophthalic acid.
SUMMARY OF INVENTION
A method for the manufacture of chlorophthalic acid comprises forming a reaction mixture comprising a mixture of about 5 to about 3 parts by weight of acetic acid to 1 part by weight of chloro-ortho-xylene, about 0.25 to about 2 mole percent, based on the chloro-ortho-xylene, of a cobalt source, about 0.1 to about 1 mole percent, based on the chloro-ortho-xylene, of a manganese source, about 0.01 to about 0.1 mole percent, based on the chloro-ortho-xylene, of a source of a metal selected from zirconium, hafnium and mixtures thereof, and about 0.02 to about 0.05 mole percent, based on the chloro-ortho-xylene, of a bromide source; maintaining the reaction mixture at a pressure of at least about 1600 kilopascals (KPa) and at a temperature of about 150° C. to about 170° C.; introducing a molecular oxygen containing gas to the reaction mixture at a rate of at least about 1.0 normal m
3
of gas/hour per kilogram (kg) of chloro-ortho-xylene in the reaction mixture to create an oxygen containing off gas from the reaction mixture, wherein the off gas oxygen concentration is less than about one percent by volume of the off gas; maintaining the introduction of the molecular oxygen containing gas until the off gas oxygen concentration exceeds about 3 percent by volume of the off gas; modifying the introduction of the molecular oxygen containing gas to maintain the off gas oxygen concentration below about 5 percent by volume of the off gas; and maintaining the modified introduction of the molecular oxygen containing gas for a time sufficient to provide at least about 90 percent conversion of the chloro-ortho-xylene to chlorophthalic acid.
In another aspect, the method for the manufacture of chlorophthalic acid comprises forming a reaction mixture comprising a mixture of about 5 to about 3 parts by weight of acetic acid to 1 part by weight of chloro-ortho-xylene, about 0.8 to about 1.2 mole percent, based on the chloro-ortho-xylene, of a cobalt source, about 0.4 to about 0.6 mole percent, based on the chloro-ortho-xylene, of a manganese source, about 0.04 to about 0.06 mole percent, based on the chloro-ortho-xylene, of a source of an ionic metal selected from zirconium, hafnium and mixtures thereof, and less than about 0.04 mole percent, based on the chloro-ortho-xylene, of a bromide source; maintaining the reaction mixture at a pressure of at least about 1600 KPa and at a temperature of about 150° C. to about 170° C.; introducing air to the reaction mixture at a rate of at least about 1.0 normal m
3
of oxygen/kg of chloro-ortho-xylene in the reaction mixture to create an oxygen containing off gas, wherein the off gas oxygen concentration is less than about one percent by volume of the off gas; maintaining the introduction of the air until the off gas oxygen-concentration exceeds about 3 percent by volume of the off gas; modifying the introduction of air so as to maintain the off gas oxygen concentration below about 5 percent by volume of the off gas; and maintaining the modified introduction of air for a time sufficient to provide at least about 90 percent conversion of the chloro-ortho-xylene to chlorophthalic acid.
In another embodiment, a method for the manufacture of chlorophthalic anhydride comprises forming a reaction mixture comprising a mixture of about 5 to about 3 parts by weight of acetic acid to 1 part by weight of a chloro-ortho-xylene, about 0.25 to about 2 mole percent, based on the chloro-ortho-xylene, of a cobalt source, about 0.1 to about 1 mole percent, based on the chloro-ortho-xylene, of a manganese source, about 0.01 to about 0.1 mole percent, based on the chloro-ortho-xylene, of a source of a metal selected from zirconium, hafnium and mixtures thereof, and about 0.02 to about 0.05 mole percent, based on the chloro-ortho-xylene, of a bromide source; maintaining the reaction mixture at a pressure of at least about 1600 KPa and at a temperature of about 150° C. to about 170° C.; introducing a molecular oxygen containing gas to the reaction mixture at a rate of at least about 1.0 normal m
3
of oxygen/kg of chloro-ortho-xylene in the reaction mixture to create an oxygen containing off gas, wherein the off gas oxygen concentration is less than about one percent by volume of the off gas; maintaining the introduction of the molecular oxygen containing gas until the off gas oxygen concentration exceeds about 3 percent by volume of the off gas; modifying the introduction of the molecular oxygen containing gas to maintain the off gas oxygen concentration below about 5 percent by volume of the off gas; maintaining the modified introduction of the molecular oxygen containing gas for a time sufficient to provide at least about 90 percent conversion of the chloro-ortho-xylene to chlorophthalic acid; removing the acetic acid and any water formed as a result of the reaction, by distillation; and dehydrating the chlorophthalic acid to form chlorophthalic anhydride.
In another aspect, the method for the manufacture of chlorophthalic anhydride comprises forming a reaction mixture comprising a mixture of about 5 to about 3 parts by weight of acetic acid to 1 part by weight of a chloro-ortho-xylene, about 0.8 to about 1.2 mole percent, based on the chloro-ortho-xylene, of cobalt acetate or cobalt acetate hydrate, about 0.4 to about 0.6 mole percent, based on the chloro-ortho-xylene, of manganese acetate or manganese acetate hydrate, about 0.04 to about 0.06 mole percent, based on the chloro-ortho-xylene, of zirconium acetate or zirconium acetate hydrate, and less than about 0.04 mole percent, based on the chloro-ortho-xylene, of sodium bromide or hydrogen bromide; maintaining the reaction mixture-at a pressure of at least about 1600 KPa and at a temperature of about 150° C. to about 170° C.; introducing air to the reaction mixture at a rate of at least about 1.0 normal m
3
of oxygen/kg of chloro-ortho-xylene in the reaction mixture to create an oxygen containing off gas,
Colborn Robert Edgar
Hall David Bruce
Koch Peter
Oeckel Gerald
Shah Mukund J.
Tucker Zachary C.
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