Optimized processing of reactor effluent in the synthesis of methacrolein from propionaldehyde and formaldehyde

A process for preparing methacrolein, the process comprising:

• a) reacting in a first reactor formaldehyde and propionaldehyde in the presence of a homogeneous catalyst mixture, which comprises at least one acid and at least one base, to obtain a reaction mixture which comprises methacrolein, water, methanol, the homogeneous catalyst mixture and unconverted formaldehyde,
• b) expanding the reaction mixture obtained in a) in an expansion vessel to obtain a gas phase which comprises methacrolein, water and methanol, and a liquid phase which comprises water, the homogeneous catalyst mixture and unconverted formaldehyde,
• c) introducing the gas phase obtained in b) into a first condenser and condensing the gas phase in the first condenser to obtain a first condensed phase,
• d) separating the first condensed phase obtained in c) in a first phase separator to obtain an organic phase which comprises methacrolein and an aqueous phase which comprises water, residuals of methacrolein and methanol,
• e) introducing the aqueous phase obtained in d) into a first distillation column, wherein the first distillation column comprises at least one column internal selected from the group consisting of trays and packing materials, and wherein the aqueous phase is introduced into the first distillation column at a first feeding point which lies above the at least one column internal,
• f) introducing the liquid phase obtained in b) into the first distillation column wherein the liquid phase is introduced into the first distillation column at a second feeding point which lies below the at least one column internal,
• g) distilling the aqueous phase and the liquid phase in the first distillation column to obtain a first overhead stream and a first bottom stream.