Chemistry Reference
In-Depth Information
O
NH
3
H
2
O
2
NH
3
N
O
2
H
O
1) H
+
O
N
N
N
2
H
4
+
2
2) OH
-
Fig. 11.31
Hydrazine manufacture
using hydrogen peroxide.
NH
H
2
O
2
/ NH
3
TS-1
Beckmann
rearrangement
O
O
NOH
Fig. 11.32
Caprolactam manufacture
with H
2
O
2
/TS-1.
recycling (Fig. 11.31). This has been operated for
over 20 years and accounts for 20-25% of world
N
2
H
4
production. Much more recently, the oxidation
of ammonia to hydroxylamine by TS-1 has been
commercialised within a new catalytic process for
caprolactam manufacture from cyclohexanone [254]
(Fig. 11.32). This process generates much less waste
than the conventional one, which can give rise to as
much as 4 t of ammonium sulfate per tonne of capro-
lactam. A patent has been issued on the preparation
of MEK oxime in a similar fashion [255]. It would
seem feasible to employ TS-1 in hydrazine manu-
facture also [256].
mixing amine and aqueous H
2
O
2
without a catalyst,
but is speeded up in the presence of tungstate
or, most notably, carbon dioxide or bicarbonate
(forming electrophilic percarbonate species as shown
in Section 2). Because the system is alkaline, addi-
tion of stabilisers is important to prevent uncon-
trolled side reactions. Among the by-products, small
amounts of nitrosamines tend to be formed. Because
these are harmful, they must be kept down to
parts-per-billion levels for most applications. This
can be done by a combination of measures: limiting
reaction temperature; using a catalyst for the main
reaction; and adding a stabiliser to suppress metal-
catalysed decompositions.
For surfactant production, manufacturing tech-
nology continues to be refined. One recent patent
[259] deals with completing the reaction in the
shipping containers, to reduce plant residence time
and/or temperature and hence improve throughput.
Another patent [260] discloses that adiabatic tem-
perature rise can be allowed during the (exothermic)
reaction while maintaining very low nitrosamine
levels through the use of CO
2
catalyst and a chelat-
ing agent. Regarding the latter, organophosphonates
such as diethylenetriamine-
N
,
N
,
N
¢,
N
≤,
N
≤-pentakis-
methylenephosphonate can be used.
4.2.1 Amine oxidations
One of the biggest current applications for H
2
O
2
is in
the manufacture of tertiary amine oxides from ter-
tiary amines [257]. Like epoxidation, this is a single
oxygen transfer reaction for which peroxygens are
the natural choice. The products are mainly of the
surfactant type, for use in a large number of house-
hold and personal care products, although another
industrially significant product is
N
-methylmorpho-
line
N
-oxide, now used as a solvent in rayon manu-
facture [258]. The reaction will proceed simply by
