Synthesis of Phenylacetic Acid

Equipment and glassware:

• Batch reactor with a thermoregulation jacket, top stirrer and thermometer;
• Nutsche-filter;
• Crystallization dishes;
• Centrifuge;
• Vacuum filtration system;

Reagents:

• Water 725 l;
• Sodium hydroxide (NaOH) 75 kg;
• Benzyl cyanide 300 kg;
• Hydrochloric acid (HCl aq 37%) 70 l;
• Activated carbon 14 kg;

Reaction Scheme

Synthesis

1. Water 650 l and sodium hydroxide (NaOH) 75 kg are added into a batch reactor.
2. Stirring is turned on for 2 h.
3. Benzyl cyanide 300 kg is added into the reactor.
4. The reaction mixture is maintained to a temperature 100 ℃.
5. The reaction mixture is stirred for 9 h.
6. Water 75 l is added into the reactor.
7. The reaction mixture is cooled down to 20 ℃.
8. Hydrochloric acid (HCl aq 37%) 70 l is poured into the reaction mixture in order to reach pH 6, temperature 20 ℃ has to be maintained.
9. Activated carbon 14 kg is then added to the mixture.
10. The reaction mixture is heated to a temperature 65 ℃.
11. This temperature is maintained with stirring for 30 min.
12. The reaction mixture is then moved into crystallization dishes through a nutsche-filter.
13. Than, cooled down to temperature 10 ℃.
14. At this temperature and stirring, phenylacetic acid is released by 37% hydrochloric acid at pH 1-2.
15. Phenylacetic acid crystallization takes about 2 h.
16. The reaction mass is moved to a centrifuge after crystallization, pressed and washed on a vacuum filter with cold water.