Process for the synthesis of isophorone in the liquid phase with recycling of by-products

Continuous process for the liquid-phase synthesis of isophorone by alkaline self-condensation of acetone, comprising the following successive steps:

• a) continuous injection through a tubular reactor (R):
• of a stream of an aqueous alkali metal hydroxide solution (A), and
• of a stream of an organic solution comprising acetone and by-products recycled via step g), followed by
• b) condensation reaction of acetone within the tubular reactor (R), the reactor containing an emulsion predominantly comprising an aqueous alkali metal hydroxide phase (B), the concentration of alkali metal hydroxide in the aqueous phase (B) within the tubular reactor being greater than or equal to 50 g/l, followed by
• c) distillation of the reaction mixture obtained from the tubular reactor (R), followed by
• d) separation of the concentrated crude reaction mixture obtained from the distillation of step c) resulting in an alkaline aqueous phase and an organic phase containing isophorone, preferably neutralization of the organic phase recovered at the end of the separation d), followed by
• e) distillation of the organic phase containing isophorone recovered in the preceding step in order to extract the polycondensation by-products predominantly at the bottom of the column (D2) and to recover a stream comprising predominantly isophorone at the top of the column (D2), followed by
• f) distillation of the polycondensation by-products from the bottom of the column (D2) obtained from the preceding distillation, followed by
• g) recycling of the stream obtained from the top of the distillation column (D3) of the preceding step comprising xylitones and/or isoxylitones to the tubular reactor (R).