Process for producing phenyl ester

Details Process for producing phenyl ester Process for producing phenyl ester

2000-03-29

2002-01-29

Carr, Deborah D. (Department: 1621)

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

Organic compounds

Fatty compounds having an acid moiety which contains the...

C554S135000, C554S162000, C560S131000, C562S408000

Reexamination Certificate

active

06342620

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to a process for producing a phenyl ester by allowing benzene, a carboxylic acid and a molecular oxygen to react with each other in the presence of a palladium catalyst.
(2) Description of the Related Art
A process for producing a phenyl ester by allowing benzene, a carboxylic acid and molecular oxygen to react with each other in the presence of a catalyst is well known. Proposals have been made wherein the reaction is conducted in the vapor phase or liquid phase using a noble metal catalyst. Palladium is most popularly used as the main ingredient of the noble catalyst, and some proposals also have been made wherein a co-catalyst comprising a metal, which exhibits by itself no catalytic activity for the specified reaction, is used in combination with the noble catalyst.
For example, a process using a palladium or platinum catalyst optionally combined with gold, silver, copper, iron or manganese is described in Japanese Examined Patent Publication (herein abbreviated to “JP-B”) S46-33024, a process using a combination of a palladium or platinum catalyst with bismuth or tellurium is described in JP-B S48-18219, and a process using a combination of a palladium catalyst with a compound comprising a metal selected from cadmium, zinc, uranium, tin, lead, antimony, bismuth, tellurium and thallium, and nitric acid is described in JP-B S55-15455.
Further, as examples of the process using a metal compound catalyst, there can be mentioned a process using a catalyst comprising a combination of an oxide, a hydroxide, an acetate or a nitrate of platinum, palladium, rhodium, ruthenium, iridium or osmium with an alkali metal nitrate (JP-B S50-34544), a process using a combination of metallic palladium or a palladium compound with nitric acid, nitrous acid or metal salts of these acids, and a metal carboxylate (Japanese Unexamined Patent Publication (hereinafter abbreviated to “JP-A”) S48-4439, and a process using a combination of palladium acetate with antimony acetate, and at least one metal acetate, the metal of which is selected from chromium, nickel, manganese and iron (JP-B H2-13653).
The processes for allowing benzene, a carboxylic acid and molecular oxygen to react with each other in the liquid phase using a palladium catalyst or a palladium compound catalyst to produce a phenyl ester have a problem such that palladium metal is dissolved in the raw material liquid, and the catalytic activity is reduced with time. Palladium is expensive and thus the above processes are costly. If a step of recovering palladium is conducted, the production processes become complicated. Further, the operation of compensating the catalytic activity decreasing with time is troublesome and not advantageous from an industrial point of view.
In a process using a metal salt catalyst soluble in a reaction liquid, a step of recovering the metal salt must be conducted. Further, a problem arises such that, for example, a palladium salt is used, palladium metal is liable to be deposited on the inner wall of a reactor during the reaction, and this also leads to reduction of catalytic activity with time and loss of palladium.
A process comprising a liquid phase reaction using as a catalyst a combination of palladium with bismuth or lead wherein a soluble bismuth compound or a soluble lead compound is additionally incorporated in the reaction system is described in JP-A S63-174950. In this process, the soluble bismuth or lead compound prevents dissolution of metallic bismuth or lead supported by the palladium catalyst, and thus, dissolution of the main catalyst ingredient, i.e., palladium can be suppressed and the reduction with time of catalytic activity can be minimized. This process has a problem such that the amount of the soluble bismuth or lead compound incorporated is large, and the soluble compound must be recovered as a crystal at the step of separating and purifying a phenyl ester, which leads to complication of the production process.
SUMMARY OF THE INVENTION
In view of the foregoing prior art, an object of the invention is to provide a process for producing a phenyl ester by allowing benzene, a carboxylic acid and molecular oxygen to react with each other in the presence of a palladium catalyst to produce a phenyl ester, wherein the undesirable dissolution of palladium is minimized and the phenyl ester can be produced under stable conditions.
In accordance with the present invention, there is provided an improvement in a process for producing a phenyl ester comprising allowing benzene, a carboxylic acid and molecular oxygen to react with each other in the presence of a palladium catalyst to produce a phenyl ester, said improvement comprising conducting the reaction in the co-presence of at least one compound selected from the group consisting of alcohols, aldehydes, cyclic hydrocarbons and formic acid.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As the palladium catalyst, known palladium catalysts can be used in the invention. The palladium catalyst contains palladium as the main catalyst ingredient. A co-catalyst may be used in combination with the palladium catalyst. The co-catalyst used includes, for example, metals such as gold, silver, copper, iron, manganese, cadmium, zinc, uranium, tin, thallium, lead, bismuth, antimony and tellurium, and compounds thereof. The metal compounds include, for example, oxides, hydroxides, nitrates, sulfates, carbonates, halides, oxyhalides, sulfides, organic carboxylates such as acetates, oxalates, naphthenates and stearates, and organic compounds. The amount of the co-catalyst is not particularly limited provided that a catalyst activity-enhancing effect is obtained. Usually the ratio of palladium to the co-catalyst metal is in the range of 1/0.01 to 1/20 by mole, and preferably 1/0.02 to 1/10 by mole.
The palladium raw material used is not particularly limited, and includes palladium metal and palladium compounds such as, for example, ammonium hexachloropalladate, potassium hexachloropalladate, sodium hexachloropalladate, ammonium tetrachloropalladate, potassium tetrachloropalladate, sodium tetrachloropalladate, potassium tetrabromopalladate, palladium oxide, palladium chloride, palladium bromide, palladium iodide, palladium nitrate, palladium sulfate, palladium acetate, potassium dinitrosulfite-palladate, chlorocarbonyl palladium, dinitrodiamminepalladium, tetraamminepalladium chloride, tetraamminepalladium nitrate, cis-diamminedichloropalladium, trans-diamminedichloro-palladium, dichloro(ethylenediamine)palladium, potassium tetracyanopalladate and acetylacetonatopalladium.
The palladium catalyst is preferably used in a state supported by a support which is inactive itself to the specified reaction. As preferable examples of the support, active carbon and silica can be mentioned. In consideration of the catalytic activity and cost, the amount of palladium is usually in the range of 0.01 to 10% by weight, preferably 0.1 to 5% by weight, based on the weight of the support.
The procedure by which the catalyst supported on a support is prepared is not particularly limited, and a conventional procedure for supporting a catalytically active ingredient on a support can be employed. For example, an impregnation, ion exchange, deposition or kneading procedure can be adopted.
When a supported catalyst including a co-catalyst is prepared by an impregnation procedure, a palladium raw material and a co-catalyst raw material can be simultaneously dissolved or dispersed in a liquid medium and a support is impregnated with the solution or dispersion. Alternatively, one of a palladium raw material and a co-catalyst raw material can be dissolved or dispersed in a liquid medium and a support is impregnated with the solution or dispersion, and then, the support is similarly impregnated with the other of the raw materials.
The as-impregnated support by an impregnation or ion-exchange procedure is subjected to conventional operations such as decantation, filtration, heating or vacuum-heating to remove the

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