Process for isolating 2-hydroxynaphthalene carboxylic acids from reaction mixtures of the alkali metal salts of 2-hydroxynaphthalene with carbon dioxide
US4057576A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 3, 1975 |
| Grant date | Nov 8, 1977 |
| Priority date | — |
| Expiry date | Jun 3, 1995 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC07C51/43
- WIPO fieldOrganic fine chemistry
- WIPO sectorChemistry
Abstract
An improved process for isolating 2-hydroxynaphthalenecarboxylic acids from reaction mixtures of the alkali metal salts of the 2-hydroxynaphthalene with carbon dioxide had been found which comprises diluting with water the reaction mixture which contains the di-alkali metal salt of 2-hydroxynaphthalenecarboxylic acid and 2-hydroxynaphthalene, while keeping the mixture at a temperature of at least 80.degree. C, then adjusting the pH-value to about 6 to 7 by means of aqueous mineral acid, separating the lower phase at at least 80.degree. C, cooling the upper phase to about 15.degree. to 25.degree. C, separating the 2-hydroxynaphthalene, then adjusting the pH-value to about 1 to 2 by means of aqueous mineral acid and isolating the separated 2-hydroxynaphthalenecarboxylic acid. By this novel process, work intensive operations, expensive technical apparatuses which are suspectible to repairs, solvents which do not participate directly in the reaction and therewith complicated regenerations, as known from the present art, are completely avoided. It permits clear and very easy separation of the reaction products at only one and the same stage in the process and allows in advantageous mann…
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