Chemistry Reference
In-Depth Information
BUTADIENE DERIVATIVES
H
EXAMETHYLENEDIAMINE
Uses
Most of the hexamethylenediamine produced is used for the
manufacture of Type 66 nylon by polymerization with
adipic acid. A minor use is for the preparation of
hexamethylene diisocyanate used in light-stable
polyurethane coatings.
Manufacture
catalyst
=
=
CH
2
CH-CH
CH
2
+ 2HCN
NC-CH
2
CH
2
CH
2
CH
2
-CN
adiponitrile
hydrogen
H
2
N-CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
-NH
2
catalyst
hexamethylenediamine
Suppliers
BASF Corp., Solutia, DuPont.
Type 66 nylon is a polyamide first commercialized by DuPont just prior to
World War II. At that time, the needed hexamethylenediamine was made
from adipic acid by reaction with ammonia to adiponitrile followed by
reaction with hydrogen. The adipic acid then, like now, was made from
cyclohexane. The cyclohexane, however, was derived from benzene obtained
from coal. The ammonia was made from nitrogen in the air by reaction with
hydrogen from water obtained in the water-gas shift reaction with carbon
monoxide from the coal. So, in the 1950s, nylon was honestly advertised by
DuPont as being based on coal, air, and water.
Hexamethylenediamine is now made by three different routes: the orig-
inal from adipic acid, the electrodimerization of acrylonitrile, and the addi-
tion of hydrogen cyanide to butadiene. Thus, the starting material can be
cyclohexane, propylene, or butadiene. Currently, the cyclohexane-based
route from adipic acid is the most costly and this process is being phased
out. The butadiene route is patented by DuPont and requires hydrogen
cyanide facilities. Recent new hexamethylenediamine plants, outside
DuPont, are based on acrylonitrile from propylene, a readily available
commodity.
