Process for producing a diaryl oxalate

Details Process for producing a diaryl oxalate Process for producing a diaryl oxalate

1997-08-07

2000-01-25

Barts, Samuel

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acid esters

C07C 6934

Patent

active

060180722

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a process for producing a diaryl ester of oxalic acid (a diaryl oxalate), for example, diphenyl oxalate (which will be abbreviated to DPO hereinafter) by disproportionation of an alkylaryl ester of oxalic acid (for example, an alkylphenyl oxalate) used as a starting material. In the process of the present invention, an alkylaryl oxalate (for example, an alkylphenyl oxalate) produced by an ester interchange reaction of a dialkyl ester of oxalic acid (a dialkyl oxalate) with a phenol compound is used as a starting material, and a diaryl oxalate, for example, DPO is produced by disproportionation of the alkylaryl oxalate.
Diaryl oxalates such as diphenyl oxalate are very important industrial materials for the production of chemical products such as carbamates.


BACKGROUND ART

As processes for producing diaryl oxalate, (1) a method in which oxalic acid and a phenol compound are directly esterified by heating them at 100 to 130.degree. C. in an organic solvent in the presence of a esterification catalyst, as disclosed in Japanese Examined Patent Publication No. 52-43,826; (2) a method in which a dialkyl oxalate is reacted with a diaryl carbonate, as disclosed in Japanese Examined Patent Publication No. 56-8,019 and Japanese Unexamined Patent Publication No. 49-42,621, and (3) a method in which a dialkyl oxalate is ester interchange-reacted with an aryl ester of a lower fatty acid, as disclosed in Japanese Examined Patent Publication No. 56-2,541 and No. 57-47,658 are known.
However, the method (1) in which oxalic acid and the phenol compound are directly esterified to produce a diaryl oxalate is disadvantageous that the reaction rate is extremely low and thus a long reaction time is necessary. Therefore the method (1) is not satisfactory from the viewpoint of industry. Also, the methods (2) and (3) in which a dialkyl oxalate is reacted with a diaryl carbonate or with an aryl ester of a lower fatty acid to produce an aryl oxalate, are not industrially satisfactory, because method (2) or (3) is disadvantageous in that the production of a starting compound consisting of the diaryl carbonate or aryl ester of lower fatty alcohol is difficult, and therefore the starting compound is expensive and difficult to obtain; and various by-products other than the target compound are produced in a large amount, and thus very complicated and troublesome refining process is necessary to isolate the diaryl oxalate.


DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a process for producing a diaryl oxalate by using an alkylaryl oxalate as a starting material, with a high productivity and a high industrial applicability.
The above-mentioned object can be attained by the process of the present invention. The process for producing a diaryl oxalate in accordance with the present invention is characterized in that an alkylaryl oxalate is subjected to a disproportionation reaction in the presence of a disproportionation catalyst, thereby to produce a diaryl oxalate, while removing a by-product comprising a dialkyl oxalate.
Also, in the process for producing a diaryl oxalate of the present invention, a dialkyl oxalate and a phenol compound are subjected to an ester interchange reaction in the presence of an ester interchange catalyst, thereby to produce an alkylaryl oxalate, while removing a by-product comprising an aliphatic alcohol; and the resultant reaction mixture containing the alkylaryl oxalate is subjected to disproportionation using the above-mentioned ester interchange catalyst contained in the reaction mixture, as a disproportionation catalyst, thereby to produce a diaryl oxalate, while removing a by-product comprising a dialkyl oxalate.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram of procedures for operating an embodiment of the production process of the present invention, and
FIG. 2 is an explanatory diagram of procedures for operating another embodiment of the production process of the present invention.


BEST MODE OF

REFERENCES:
patent: 3471549 (1969-10-01), Hulsmann
patent: 4451664 (1984-05-01), Ranade
patent: 4482732 (1984-11-01), Ranade
patent: 4482733 (1984-11-01), Ranade

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