4.Production method

Obtained by acetylation of paraminophen.
Method 1: Add p-aminophenol to dilute acetic acid, then add glacial acetic acid, temperature rise to 150ºC for 7h, , reaction for 2h, check the end point, qualified, cool to below 25ºC, filter, wash until no acetic acid taste, shake dry, coarse product.
Method 2: para-aminophenol, glacial acetic acid and acid mother liquor containing more than 50% acid were distilled together, and the rate of evaporation of dilute acid was 1/10 of the total amount of distillate per hour
First, when the internal temperature rises to more than 130ºC, sample to check the residual amount of p-aminophenol is less than 2.5%, add dilute acid (content of more than 50%), cooling crystallization. Filter, first with a small amount of dilute acid washing, and then with a lot of water to filtrate close to colorless, coarse product.
The yield of method 1 is 90%.
The yield of method 2 is 90-95%. Refining method: When the water is heated to the near boiling point, the crude product is put into it. Add activated carbon soaked in water, adjust with dilute acetic acid to pH=4.2-4.6, and boil for 10min. Press and filter the filtrate with a small amount. Cooling to below 20ºC, crystallization. The product was filtered, washed and dried to produce paracetamol.