Optimized process for preparing methacrylic acid

A process for continuously preparing methacrylic acid, comprising:

• a first process step comprising preparing methacrolein from formaldehyde and propionaldehyde with at least one acid and at least one organic base as catalysts in a reactor 1 to obtain a converted reaction solution comprising methacrolein and a catalyst-containing aqueous phase, then
• a second process step comprising:
• separating methacrolein from the catalyst-containing aqueous phase and oxidizing the methacrolein to methacrylic acid with a heterogeneous catalyst in the presence of oxygen and water in a reactor 2, to obtain a process gas, then
• condensing and quenching the process gas to produce an aqueous crude methacrylic acid, and then
• separating the methacrylic acid from an aqueous phase of the aqueous crude methacrylic acid with an extractant to obtain an extracted aqueous phase comprising carboxylic acids, and
• recycling the extracted aqueous phase into reactor 1.