Method for synthesizing cyanobenzene by recycling and reusing byproducts of benzotripolycyanamide

The invention provides a method for synthesizing benzonitrile by recycling and reusing byproducts of benzotripolycyanamide, which is characterized in that the byproducts 2, 4, 6 triphenyl-1, 3, 5-triazine, benzamide and the like which are dissolved and recycled in washing water in the production process of the benzotripolycyanamide are used as main raw materials. Firstly, the 2, 4, 6-triphenyl-1, 3, 5-triazine is subjected to acidolysis to obtain benzamidine, benzoic acid and ammonia gas, and the benzoic acid and the ammonia gas generate ammonium benzoate on site; then benzamidine, ammonium benzoate, benzamide and other components are heated and dehydrated under the chelation of nickel chloride to generate benzonitrile; and finally, crude distillation and rectification are performed to obtain the high-purity benzonitrile. A plurality of byproducts and intermediates are converted into benzonitrile and high-boiling residues through ingenious design. According to the method, the treatment difficulty and cost of