Page 158 - Chemical and process design handbook

Speight_Part II_B 11/7/01 3:11 PM Page 2.99

BUTANEDIOL

1,4-butanediol (tetramethylene glycol, 1,4-butylene glycol; melting point:
o
o
o
20.2 C, boiling point: 228 C, density:1.017, flash point: 121 C) was first
prepared in 1890 by acid hydrolysis of N,N′-dinitro-1,4-butanediamine.
Other early preparations were by reduction of succinaldehyde or succinic
esters and by saponification of the diacetate prepared from 1,4-dihalobutanes.
Catalytic hydrogenation of butynediol, now the principal commercial route,
was first described in 1910.
Butanediol is manufactured by way of hydrogenation of butynediol (the
Reppe process):
HC≡CH + 2HCHO → HOCH C≡CCH OH →
2 2
HOCH CH CH CH OH
2 2 2 2
An alternative route involving acetoxylation of butadiene and has come
on stream, and, more recently, a route based upon hydroformylation of
allyl aIcohol has also been used. Another process, involving chlorination
of butadiene, hydrolysis of the dichlorobutene, and hydrogenation of the
resulting butenediol, has been practiced.
A more modern process involves the use of maleic anhydride as the
starting material. In the process (Fig. 1), maleic anhydride is first esterified
with methanol and the ester is fed to a low-pressure vapor-phase hydro-
genation system where it is converted to butanediol.
Butanediol is specified as 99.5% minimum pure, determined by gas chro-
o
matography, solidifying at 19.6 C minimum. Moisture is 0.04% maximum,
determined by Karl Fischer analysis (directly or by a toluene azeotrope).
Butanediol is much less toxic than its unsaturated analogs and it is neither
a primary skin irritant nor a sensitizer. Because of its low vapor pressure, there
is ordinarily no inhalation problem but, as with all chemicals, unnecessary
exposure should be avoided.
The uses of butanediol are determined by the chemistry of the two pri-
mary hydroxyls. Esterification is normal and it is advisable to use nonacidic

2.99