Method for partially extracting butanol from an aqueous solution comprising ethanol and butanol

A process for treating an hydroalcoholic feedstock comprising water, ethanol and butanol in order to produce an ethanol-rich effluent, a water-rich effluent and a butanol-rich effluent, comprising:

• a) a water-ethanol separation step, comprising a water-ethanol separation section comprising a distillation column comprising at least 14 theoretical plates and having a reflux ratio of less than or equal to 1.2, said water-ethanol separation section comprising:
• a feed of said hydroalcoholic feedstock, located at the level of or downstream of the third theoretical plate,
• the side withdrawal of an hydroalcoholic solution comprising butanol in the butanol accumulation zone of the distillation column located downstream of the feed,
• an injection of the heavy phase resulting from step b), located downstream of and close to the withdrawal,
• an injection of the ethanol-water distillate resulting from step c), located upstream of the feed and close to the top of said distillation column,
• said distillation section producing, at the top of the column, an ethanol-rich effluent and, at the bottom of the column, a water-rich effluent;
• b) a demixing step comprising
• a section for mixing said hydroalcoholic solution withdrawn in step a) with the water/butanol/ethanol fraction withdrawn in step c);
• a section for decanting the previous mixture, comprising a decantation tank in which the pressure is less than or equal to 6 bar absolute, said decanting section producing a heavy phase mainly containing water and a light phase;
• c) a butanol separation step, comprising a butanol distillation section comprising at least one distillation column fed with the light phase resulting from step b) and comprising a side withdrawal of a water/butanol/ethanol fraction, located on said column in a zone between the feed and the bottom of the column, said butanol distillation section producing, at the bottom of the column, a butanol-rich effluent and, at the top of the column, an ethanol-water distillate.