Questions regarding the synthesis of β-alanine

Acrylonitrile reacts with ammonia in a solution of diphenylamine and tert-butanol to produce β-aminopropionitrile, which is then obtained via alkaline hydrolysis. In a dry autoclave, acrylonitrile, diphenylamine, and tert-butanol are added sequentially; stirring is carried out for 5 minutes. Then liquid ammonia is added, the temperature is maintained at 100–109°C, the pressure is around 1 MPa, and stirring continues under these conditions for 4 hours. Stop stirring when the temperature drops below 10°C and the pressure returns to atmospheric pressure. tert-Butanol is recovered under reduced pressure at 65–70°C/（8.0–14.7 kPa), yielding crude β-aminopropionitrile. The crude product is then subjected to vacuum distillation, with the fraction collected at 66–105°C/（1.33–4.0 kPa) providing β-aminopropionitrile. The alkaline hydrolysis is carried out in a reaction tank: liquid alkali is first added, the temperature is maintained at 90–95°C, and β-aminopropionitrile is slowly added while stirring; after addition, the mixture is held at this temperature for 1 hour. Evaporate under reduced pressure for half an hour to remove ammonia from the reaction solution, add an appropriate amount of water, and add salt acid dropwise until the pH reaches 7-7.2. Filter to remove a small amount of insoluble impurities. The filtrate is concentrated under reduced pressure until a large amount of solid precipitates; it is then discharged while still hot. After cooling to below 10°C, filtration is carried out followed by vacuum drying to obtain β-alanine. This method consumes 982 kg of β-aminopropionitrile per ton of product, with a yield of 90% in the alkaline hydrolysis stage.

Acrylonitrile reacts with ammonia in a solution of diphenylamine and tert-butanol to produce β-aminopropionitrile, which is then obtained via alkaline hydrolysis. In a dry autoclave, acrylonitrile, diphenylamine, and tert-butanol are added sequentially; stirring is carried out for 5 minutes. Then liquid ammonia is added, the temperature is maintained at 100–109°C, the pressure is around 1 MPa, and stirring continues under these conditions for 4 hours. Stop stirring when the temperature drops below 10°C and the pressure returns to atmospheric pressure. tert-Butanol is recovered under reduced pressure at 65–70°C/（8.0–14.7 kPa), yielding crude β-aminopropionitrile. The crude product is then subjected to vacuum distillation, with the fraction collected at 66–105°C/（1.33–4.0 kPa) providing β-aminopropionitrile. The alkaline hydrolysis is carried out in a reaction tank: liquid alkali is first added, the temperature is maintained at 90–95°C, and β-aminopropionitrile is slowly added while stirring; after addition, the mixture is held at this temperature for 1 hour. Evaporate under reduced pressure for half an hour to remove ammonia from the reaction solution, add an appropriate amount of water, and add salt acid dropwise until the pH reaches 7-7.2. Filter to remove a small amount of insoluble impurities. The filtrate is concentrated under reduced pressure until a large amount of solid precipitates; it is then discharged while still hot. After cooling to below 10°C, filtration is carried out followed by vacuum drying to obtain β-alanine. This method consumes 982 kg of β-aminopropionitrile per ton of product, with a yield of 90% in the alkaline hydrolysis stage.