PEP Review IX-1-5
Aniline, Amination of Benzene
Published: September 1973
The economics of producing aniline via nitrobenzene were evaluated in the Process Economics Program Report No. 76. The nitrobenzene route was shown to be far superior to the other two routes evaluated, namely the ammonolysis of phenol and the ammonolysis of cyclohexanol.
German patent 2,114,255 issued in 1971 and assigned to Du Pont claims the direct amination of benzene with ammonia in the presence of water. The reaction is catalyzed by a nickel/nickel oxide catalyst that may contain other oxides such as zirconium, aluminum, or silicon. Under the preferred conditions, approximately 10% per pass yield of aniline are reported on the benzene feed. The reaction time is slightly over 10 minutes and the reaction is conducted in the liquid phase.
The same catalyst system is also effective in producing meta- or ortho-phenylenediamine. Meta-phenylenediamine has commercial significance as the starting material for dyestuff manufacture and, as the component of a polyamide fiber, Nomex@, marketed by Du Pont. The ortho isomer has little commercial significance. Catalysts that contain an oxide or carbonate of strontium, magnesium, or cerium favor the formation of metaphenylenediamine, as do higher ratios of catalyst to benzene. The per pass yield on aniline fed is generally low, around 7%.