Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Patent
1989-06-14
1991-12-10
Killos, Paul J.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
562423, C07C 5115
Patent
active
050720368
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a process for preparing para-hydroxybenzoic acid using the Kolbe-Schmitt process.
Para-hydroxybenzoic acid finds a wide variety of applications as starting material for polymeric materials. Particularly in these days, it draws attention as starting material for liquid crystalline polyesters having high strength and high heat resistance. Also alkyl esters of para-hydroxybenzoic acid are useful as antimolds for cosmetics and industrial materials.
Industrial preparation of para-hydroxybenzoic acid in the prior art is by solid-gas phase reaction involving reacting powdered potassium phenolate with carbon dioxide at elevated temperatures under pressure which is known as the Kolbe-Schmitt process.
As is well known from the past, the Kolbe-Schmitt reaction is to react an alkali phenolate with carbon dioxide at elevated temperatures under pressure. The use of sodium phenolate as the reactant results in salicylic acid and the use of potassium phenolate predominantly results in para-hydroxybenzoic acid. In fact, a number of patents were issued on the preparation of para-hydroxybenzoic acid utilizing such solid-gas phase reaction.
Many of these preparation processes succeeded in preparing salicylic acid in as high yields as about 90%. As to para-hydroxybenzoic acid, however, all the processes available as far can prepare the end product in yields of at most 50%. In recent years, it was proposed to use various inert reaction media.
To name a few, the recently proposed methods use aprotic polar solvents (Japanese Patent Publication No. 29942/1968), aromatic hydrocarbons and aromatic ethers (Japanese Patent Publication Nos. 1617/1966 and 30063/1975), diaryls, diaryl alkanes, triaryl alkanes or hydrogenated ones thereof (Japanese Patent Application Kokai No. 164751/1984), and kerosine or gas oil (Japanese Patent Publication No. 12185/1977), producing para-hydroxybenzoic acid in a yield of 44%, 47%, 54%, 78% and 53%, respectively.
In contrast, salicylic acid can often be produced by reaction using a reaction medium in high yields of about 90% as in the case of solid-gas phase reaction.
Improvements in these methods were made by the co-existence of phenol in the reaction system as proposed in Japanese Patent Publication No. 37658/1975, Japanese Patent Application Kokai No. 115053/1986, and Japanese Patent Publication No. 9529/1970, which report a para-hydroxybenzoic acid yield of 64%, 78% and 75%, respectively.
These improved methods, however, are essentially mere modifications of the type of reaction medium or limitations of reaction conditions. They are not yet regarded high in the percent yield of para-hydroxybenzoic acid produced which is of primary importance in the synthetic chemical industry.
Therefore, an object of the present invention is to provide a process for preparing in high yields para-hydroxybenzoic acid which finds a wide variety of applications as the starting material for various polymeric materials.
SUMMARY OF THE INVENTION
The above object is achieved by the present invention as defined below.
According to the present invention, there is provided a process for preparing para-hydroxybenzoic acid, comprising reacting an alkali metal salt of phenol except the lithium and sodium salts with carbon dioxide in the presence of at least one compound selected from compounds of the following formulae (I) and (II): ##STR2##
In formulae (I) and (II), M is an alkali metal except lithium and sodium.
In formula (I), R is any substituent except an aliphatic hydroxy group having up to 4 carbon atoms, an aliphatic mercapto group having up to 4 carbon atoms, a substituent having at least one of them as its structural unit, and a hydrogen atom.
In formula (II), R' is any substituent except an aliphatic hydroxy group having up to 4 carbon atoms, an aliphatic mercapto group having up to 4 carbon atoms, and a substituent having at least one of them as its structural unit.
In formula (I), n is an integer of 1 to 5, and R groups may be the same or different when n is mo
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patent: 4034006 (1977-07-01), Lind et al.
patent: 4036873 (1977-07-01), Huffman
patent: 4072707 (1978-02-01), Grosso
patent: 4508920 (1985-04-01), Stopp et al.
patent: 4529817 (1985-07-01), Stopp et al.
Iizuka Tokio
Ijiri Makiko
Saima Hitoshi
Suzuki Toshinobu
Wakui Tadahiro
Kawasaki Steel Corporation
Killos Paul J.
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