Aniline Halcon process

A key feature of the Halcon process is the use of low pressure distillation (less than 80 kPa = 12 psi) to break the pbenol—aniline a2eotrope and allow economical separation of aniline from phenol (67). 

Aniline can also be prepared by the amination of phenols under a pressure of 15 to 16 atm at a temperature of 380 to 385°C in the presence of a silica- alumina catalyst (Halcon process). 

In the Halcon process, the amination of 7 takes place in the vapor phase with a silica-alumina catalyst (Scheme 3). Amination of phenol has the advantage of reduced capital costs, long catalyst life and high quality product. Excess ammonia favors high conversion of the mildly exothermic (AH = —544 kcal ruol 1) and reversible reaction, and also minimizes formation of byproducts. Generally, however, the price of phenol makes this process more expensive than the nitrobenzene routes. The last plant in the US to produce aniline from phenol by amination was operated by Sunoco Chemicals. It produced 140 million lbs./year-1, with diphenylamine, or DPA (8) as a coproduct, at Haverhill, Ohio, and ceased production in 200213,14. Aristech Chemical Corporation at one time operated a phenol-to-aniline process in the US. 

The ammonolysis of phenol (61—65) is a commercial process in Japan. Aristech Chemical Corporation (formerly USS Chemical Division of USX Corporation) currently operates a plant at Ha verb ill, Ohio to convert phenol to aniline. The plant s design is based on Halcon s process (66). In this process, phenol is vapori2ed, mixed with fresh and recycled ammonia, and fed to a reactor that contains a proprietary Lewis acid catalyst. The gas leaving the reactor is fed to a distillation column to recover ammonia overhead for recycle. Aniline, water, phenol, and a small quantity of by-product dipbenylamines are recovered from the bottom of the column and sent to the drying column, where water is removed. 

Aniline can also be produced when phenol is subjected to gas-phase ammonolysis at 200 bar and 425°C in an adiabatic, fixed-bed reactor. This is the Halcon/Scientific Design process. The chemistry is ... 

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