Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2001-05-22
2002-06-25
Aulakh, Charanjit S. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
active
06410753
ABSTRACT:
BACKGROUND OF THE INVENTION
1) Field on the Invention
The present invention relates to a process for producing trimellitic anhydride from trimellitic acid obtained by liquid phase oxidation of pseudocumene, in which obtained trimellitic anhydride is not colored and contents of by-products are very small.
2) Prior Art
Trimellitic anhydride which is an aromatic triacidic base is important as a raw material of high grade plasticizers or heat resisting plastics.
Trimellitic anhydride, for example, as described in Japanese Patent Kokai (Laid-open) No.61-280448, is produced by a process comprising heat dehydrating at a temperature of 220 to 230° C. crude trimellitic acid obtained by oxidation of pseudocumene with molecular oxygen in the presence of a catalyst comprising bromine ion or both bromine ion and a heavy metal(s) and then performing vacuum distillation.
Trimellitic anhydride produced by above-mentioned process does not always satisfy its quality. In recent years, further high quality of trimellitic anhydride has been required as a raw material of high grade plasticizers or heat resisting plastics.
Trimellitic acid is produced by oxidation of pseudocumene with air in the presence of a heavy metal catalyst in the same manner as in other alkyl aromatic compounds. Since two carboxyl groups in trimellitic acid thus produced have ortho-structure to each other, trimellitic acid forms a complex with a heavy metal(s) to degrade catalyst activity. Thus, it is known that the yield of trimellitic acid in use of psuedocumene is lower than that in use of alkyl aromatic compounds having no such structure.
Thus, various improvements in catalysts for oxidation of psuedocumene or other alkyl aromatic compounds have been performed. U.S. Pat. No. 3,920,735 describes that Mn—Br catalysts and Co—Mn—Br catalysts are improved by addition of zirconium. Japanese Patent No.2939346 describes a process for oxidation of psuedocumene comprising further using cerium in addition to a Co—Mn—Zr—Br catalyst and adding a Co—Mn—Zr—Ce—Br catalyst step by step. Japanease Patent Kokai (Laid-Open) No.5-221919 describes a process for oxidation of psuedocumene comprising a Co—Mn—Ce—Ti—Br catalyst step by step.
Trimellitic acid is usually dehydrated to change to trimellitic anhydride, which is used as an intermediate to synthesize resins or plasticizers. It is desired that trimellitic anhydride thus obtained and resins used it are not colored.
Japanese Publication (of PCT Application) No.4-501271 discloses a process for improving color of trimellitic anhydride comprising adding boron oxide of 0.1% by weight or above to trimellitic anhydride and performing heat treatment and then performing distillation.
The inventors oxidized psuedocumene according to the processes described in Japanese Patent No.2939346 and Japanese Patent Kokai (Laid-open) No.5-221919 and dehydrated trimellitic acid thus obtained to change trimellitic anhydride. Trimellitic anhydride thus obtained was colored to some degree.
In conventional processes for producing trimellitic anhydride, organic bromine compounds including, typically, bromotrimellitic acid are often by-produced since bromine ion is used as an oxidation catalyst. The organic bromine compounds are remained in distillation-purified trimellitic anhydride since they are difficult to separate, so that they exert bad influence on plasticizers or heat resisting plastics to use trimellitic anhydride as a raw material.
Thus, a process for producing trimellitic anhydride in which obtained trimellitic anhydride is not colored and contents of by-products such as organic bromine compounds are very small has been required.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a process for producing trimellitic anhydride comprising performing liquid phase oxidation of psuedocumene to obtain trimellitic acid and producing trimellitic anhydride from trimellitic acid thus obtained, in which trimellitic anhydride is not colored and contents of by-products such as organic bromine compounds are very small.
As a result of extensive studies to solve above-mentioned prior art problems, the inventors have found that that trimellitic acid is produced by liquid phase oxidation of psuedocumene containing a specific amount of dimethyl benzaldehyde as raw material for oxidation and then intended trimellitic anhydride which is not colored can be produced from trimellitic acid thus obtained and furthermore trimellitic acid in which contents of by-products such as organic bromine compounds can be produced by heat treating trimellitic acid and/or trimellitic anhydride produced in above-mentioned process in the presence of a Ni catalyst for a long time and then purifying trimellitic anhydride thus obtained by distillation, and have accomplished the present invention.
The present invention provides to a process for producing trimellitic anhydride which comprises performing liquid phase oxidation of pseudocumene containing 5% by weight or above of dimethyl bezaldehyde as a raw material for oxidation with air in aliphatic monocarboxylic acid having 1 to 5 carbon atoms as a solvent in the presence of a catalyst comprising both each metal of cobalt, manganese and zirconium and bromine to obtain trimellitic acid and then heat dehydrating trimellitic acid thus obtained, thereby producing trimellitic anhydride.
The present invention provides to a process for producing trimellitic anhydride which comprises performing liquid phase oxidation of pseudocumene containing 5% by weight or above of dimethyl bezaldehyde as a raw material for oxidation with air in aliphatic monocarboxylic acid having 1 to 5 carbon atoms as a solvent in the presence of a catalyst comprising both each metal of cobalt, manganese and zirconium and bromine to obtain trimellitic acid and then heat treating trimellitic acid thus obtained in the presence of a catalyst comprising 10 ppm or above of Ni to trimellitic acid at a temperature of 200° C. or above for 30 minutes or above to produce trimellitic anhydride and then separating trimellitic anhydride thus produced by distillation.
Further, the present invention provides to a process for producing trimellitic anhydride which comprises performing liquid phase oxidation of pseudocumene, dimethyl benzaldehyde and/or oxide derivative of dimethyl benzaldehyde as raw material for oxidation with air in a solvent in the presence of a catalyst comprising a bromine compound to obtain trimellitic acid and then heat treating trimellitic acid thus obtained in the presence of a catalyst comprising 10 ppm or above of Ni to trimellitic acid and/or trimellitic anhydride at a temperature of 200° C. or above for 30 minutes or above to produce trimellitic anhydride and then separating trimellitic anhydride thus produced by distillation.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below.
As psuedocumene to be used as a raw material for oxidation in the present invention, commercial psuedocumene separated by distillation from C
9
distillate in a catalytic reforming oil or a thermal decomposition residual oil can be used.
As dimethyl benzaldehyde to be used as a raw sub-material for oxidation, 3,4-dimethyl benzaldehyde, 2,4-dimethyl benzaldehyde, 2,5-dimethyl benzaldehyde and a mixture thereof can be used.
Dimethyl benzoic acids including 3,4-dimethyl benzoic acid, 2,4-dimethyl benzoic acid and 2,5-dimethyl benzoic acid may be contained in the raw material for oxidation.
In the present invention, psuedocumene containing dimethyl benzaldehyde of 5% by weight or above is used as the raw material for oxidation. It is preferable that the raw material for oxidation contains dimethyl benzaldehyde of 6% by weight or above. When the raw material contains dimethyl benzaldehyde, oxidation of psuedocumene is promoted and combustion and side reactions are decreased, so that the oxidation yield is improved. Thus, in subsequent dehydration, the product is not colored. Further, the content of 2,4-dimethyl benzaldehyde in psuedocumene is suitably decided in the above-mentioned range
Maruki Ikutaro
Ogawa Hiroshi
Tanaka Kazuo
Armstrong Westerman & Hattori, LLP
Aulakh Charanjit S.
Mitsubishi Gas Chemical Company Inc.
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