| 摘要 |
Continuous process for the manufacture of beta -isophorone from alpha -isophorone, itself obtained by the trimerization of acetone in an alkaline medium. beta -Isophorone (3,5,5-trimethyl cyclohexa-3-en-1-one (I) is prepared continuously from alpha -isophorone (3,5,5-trimethyl cyclohexa-2-en-1-one (II) in the following stages: (a) (II) and an alkaline hydroxide solution (preferably KOH in methanol or ethanol) are introduced into a reaction zone; (b) they are heated under reflux at least 150 (preferably 190 - 216) degrees C, and at a pressure P1 below or equal to atmospheric; (c) continuously and simultaneously (I) is eliminated in the vapor phase by distillation at a pressure P2 that is below P1, and at a temperature of 150 degrees C or above, and heavy products are drawn off such that their weight is at most 7 % of the reaction mixture; and (d) the condensates from the distillation at the reaction zone are collected.
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