Page 23 - Chemical and process design handbook

Speight_Part 1_A 11/7/01 3:04 PM Page 1.9

AMINATION 1.9
through reduction use expensive reagents (iron, Fe, zinc, Zn, or hydrogen,
H , gas) that make ammonolysis costs quite attractive. Substituted amines
2
can be produced by using substituted ammonia (amines) in place of sim-
ple ammonia. The equipment is an agitated iron pressure vessel; stainless
steel is also used for vessel construction.
Amination by reduction is usually carried out in cast-iron vessels (1600
gallons capacity, or higher) and alkali reductions in carbon steel vessels of
desired sizes. The vessel is usually equipped with a nozzle at the base so
that the iron oxide sludge or entire charge may be run out upon completion
of the reaction.
In some reducers, a vertical shaft carries a set of cast-iron stirrers to keep
the iron particles in suspension in the lower part of the vessel and to main-
tain all the components of the reaction in intimate contact. In addition, the
stirrer assists in the diffusion of the amino compound away from the sur-
face of the metal and thereby makes possible a more extensive contact
between nitro body and catalytic surface.
Thus, amination, or reaction with ammonia, is used to form both aliphatic
and aromatic amines. Reduction of nitro compounds is the traditional process
for producing amines, but ammonia or substituted ammonias (amines) react
directly to form amines. The production of aniline by amination now exceeds
that produced by reduction (of nitrobenzene).
Oxygen-function compounds also may be subjected to ammonolysis,
for example:

1. Methanol plus aluminum phosphate catalyst yields monomethylamine
(CH NH ), dimethylamine [(CH )2NH], and trimethylamine
3
3
2
[(CH )3N]
3
2. 2-naphthol plus sodium ammonium sulfite (NaNH SO ) catalyst
3
3
(Bucherer reaction) yields 2-naphthylamine
3. Ethylene oxide yields monoethanolamine (HOCH CH NH ),
2
2
2
diethanolamine [(HOCH CH ) NH)], and triethanolamine
2
2 2
[(HOCH CH ) N)]
2
2 3
4. Glucose plus nickel catalyst yields glucamine
5. Cyclohexanone plus nickel catalyst yields cyclohexylamine
Methylamines are produced by reacting gaseous methanol with a cata-
o
lyst at 350 to 400 C and 290 psi (2.0 MPa), then distilling the reaction mix-
ture. Any ratio of mono-, di-, or trimethylamines is possible by recycling
the unwanted products.