| 摘要 |
1,201,472. Purification of organic acids. TENNECO CHEMICALS Inc. 3 Oct., 1967 [5 Oct., 1966], No. 44950/67. Heading C2C. A sublimable aromatic monocarboxylic acid having on its aromatic nucleus one or more substituents additional to the carboxyl group is purified by heating it with a gas which is inert to the acid, e.g. air, nitrogen or carbon dioxide, and is heated to a temperature sufficient to effect sublimation, the heating of the acid being effected in the presence of at least 0À5% by weight based on the acid of a finely-divided solid activated adsorbent, and cooling the resulting sublimate gas stream in a separate zone to obtain the purified acid. Suitable adsorbents include, for example, acid-activated clays such as fuller's earth, kieselguhr, flondin and montmorillonite, and activated silica gel, alumina and carbon. Suitable acids for purification by the process are, for example, salicylic acid, p-hydroxybenzoic acid, 2,3,4-trihydroxybenzoic acid, 5 - hydroxy - 1 - naphthoic acid, o-, m- and p-chlorobenzoic acids, o-bromobenzoic acid, m- and p-iodobenzoic acid, 2,4- and 3,4-dibromobenzoic acids, 2,4-, 2,6-, 3,4- and 3,5-dichlorobenzoic acids, 2,3,5- and 3,4,5 - trichlorobenzoic acids, m - aminobenzoic acid, p-nitrobenzoic acid and m- and p-benzylbenzoic acids. The impure salicylic acid used as starting material may be obtained by the treatment of an alkali metal phenate with carbon dioxide.
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