15733-89-8

141-82-2

91-56-5

15733-89-8

1. Add 400kg of recovered glacial acetic acid to the 1000L reactor and start stirring. 2. 100kg of indigo, 160kg of malonic acid and 15kg of sodium acetate were added sequentially to the reactor to ensure adequate mixing. 3. The reaction mixture was heated to reflux and the reflux reaction was maintained for 6 hours. 4. Upon completion of the reaction, the acetic acid was removed by distillation under reduced pressure. 5. 300 kg of deionized water was added to the reaction mixture and stirred to promote crystal formation. 6. 6. The solid product was collected by filtration, washed with 30 kg of cold glacial acetic acid, and then rinsed with 30 kg of cold methanol to obtain the wet product of 2-quinolinone-4-carboxylic acid. 7. The wet product was dried at 45-70 °C for 24 h. 125 kg of 2-quinolinone-4-carboxylic acid was finally obtained with a yield of 97.3% and a liquid phase purity of 99.6%.