| 摘要 |
beta-isophorone is formed by isomerizing alpha-isophorone in the presence of an isomerizing catalyst (an aliphatic C5-20 polycarboxylic acid) in an isomerizing-reaction unit 1. The beta-isophorone thus formed is oxidized with oxygen in an inert solvent in the presence of an oxidizing catalyst (a complex salt of a transition metal and an N,N'-disalicylidenediamine) in an oxidizing-reaction unit 2, thereby forming ketoisophorone. After removing a low-boiling point component, which is an impurity (non-conjugated cyclic ketone), from the reaction mixture using a distilling unit 3, a high-boiling component (oxidizing catalyst) is separated in a distilling unit 4, and then ketoisophorone is separated from the solvent in the separation unit 5. Thereafter, the solvent containing 0 to 5,000 ppm (weight basis) of the impurities and substantially free from ketoisophorone is recycled to the oxidizing reaction through a recycling line 6. According to the present invention, the combination of the isomerizing reaction and the oxidizing reaction makes it possible to produce ketoisophorone from alpha-isophorone while maintaining the activity of the oxydizing catalyst.
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