High pressure synthesis of diphenylamine from aniline and phenol

Abstract The synthesis of diphenylamine from aniline and phenol has been carried out in the presence of a phosphoric acid catalyst. Very high pressure has no beneficial effect on the synthesis of diphenylamine. Under optimum conditions (558 K 0.552 × 10 6 N m −2 ; residence period 2 h; aniline to phenol mol ratio, 1:3 and aniline to catalyst mol ratio, 1:0.3232), the conversion of aniline to diphenylamine was 72.57%.