| 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 to at least 150 (preferably 185 - 216 degrees C); (c) the reaction mixture is eliminated continuously by two means, firstly by distillation at 150 - 216 degrees C and a pressure of 350 mbar or up to atmospheric to isolate a fraction containing 30-90% (I) (preferably 50 - 70 % (I)), and secondly by drawing off the heavy products from the reaction, such that their content in the reaction mixture is at most 7 %; (d) the distillate from (c) is distilled under reduced pressure at 100 - 150 degrees C to give a product in which the ratio (I)/(II) is at least 99 %; and (e) (e) the distillation residue is returned continuously to the reaction zone.
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