| 摘要 |
Hydroxyterephthalic acid or its alkali metal salts are prepared by heating an alkali metal salt of m-hydroxybenzoic acid at temperatures above 230 DEG C. with an alkali metal carbonate or bicarbonate and excess carbon dioxide and, if desired, converting the alkali metal salt thus obtained to the acid in known manner. It is desirable to mix the starting materials with finely-divided inert substances, e.g. sand, kieselguhr, silica, metal powders or turnings, finely divided metal oxides such as alumina, and inert salts such as sodium sulphate. Preferably the reaction is carried out at superatmospheric pressure, e.g. 5-50 atm. If desired a catalyst, e.g. cadmium oxide, may be present. The salts may be converted to the acid by dissolving in water and treating the solution with acid, e.g. hydrochloric acid. |
