PROCESS FOR PREPARING N,N-DIPHENYL-P-PHENYLENE DIAMINE Russian patent published in 1999 - IPC

FIELD: technology of organic synthesis. SUBSTANCE: -n-- diphenyl-p-phenylene diamine is prepared by condensation of hydroquinone with aniline in presence of catalyst. Catalyst is 85-89% phosphoric acid. Hydroquinone, aniline and phosphoric acid are mixed at molar ratio of 1:(1.2-1.35): (0.018-0.10), respectively. Reaction mixture is heated to 205-210 C. Azeotropic distillation of the resulting water is carried out at elevated temperature of 235-240 C for 1.5-2.5 h, condensate is separated into aqueous and aniline phases and aniline phase is directed for recycling. Aniline is then added to reaction mixture for 2-8 h till hydroquinone: aniline moles ratio of 1: (2.05-2.5), respectively is achieved. This operation is simultaneously accompanied with azeotropic distillation of the resulting water, said process being carried out for 2-8 h indicated above at elevated temperature at rate of 3-10 C/h. Reaction mixture is then maintained at attained temperature for 1.5-3 h, and unreacted aniline is removed. -n-- diphenyl-p-phenylene diamine is recovered from the remaining reaction mixture. The process makes it possible to attain high and stable yield of the desired product at optimum combination of technological modes of the claimed process and optimum concentrations of the ingredients used. EFFECT: more efficient preparation process. 8 cl, 2 ex