Environmental Engineering Reference
In-Depth Information
2-iodopropane and silver nitrate [
58
]. In British patent [
55
], isopropanol was
continuously nitrated in urea. At the temperature of the boiling point of nitric acid,
isopropanol and urea were added into nitric acid with concentration of over 40 %.
Unstable products were removed by a
flowing gas. The theoretical yield of iso-
propyl nitrate obtained by this method is 80 % [
59
]. The main methods to prepare
isopropyl nitrate include (1) sliver nitrate
fl
alkyl halide reaction, (2) nitration by the
mixed acids of nitric acid and sulfuric acid, and (3) inert adsorption nitration
[
60
,
61
]. Based on those preparation methods, The writer [
15
,
62
-
64
] invented the
dual inert complementary adsorption nitration. In the method, the concentration of
nitric acid is over 50 % and the reaction temperature is 108
-
C. Commercial
production of isopropyl nitrate has been done by this method. A certain amount of
urea and ammonium nitrate is used in the method to absorb nitrogen oxides, which
will be oxidized to isopropyl nitrate. The isopropyl nitrate would be catalytically
hydrolyzed at high temperature. The reaction mechanism can be expressed as the
following equation.
110
°
-
ð
NH
Þ
2
CO
þ
NH
4
NO3
½100
105
C
ð
CH
3
Þ
2
CHOH + HNO
3
!
ð
CH
3
Þ
2
CHONO
2
þ
H
2
O
The inert adsorption nitration is suitable for commercial production of isopropyl
nitrate because of its features, such as simple procedure, cheap raw materials, low-
cost production, and easy treatment of waste acid. The procedure is described
below.
70 % nitric acid is poured into a stainless steel reactor, and then urea and
ammonium nitrate are added in proportion. The temperature is slowly increased to
70
C under agitation till the urea and ammonium nitrate are completely dis-
solved. The temperature is then increased to 95
-
100
°
C and isopropanol is drop-
wisely added by a dropping funnel with the end under the solution. Cooling water
and vacuum systems are used to pump out the produced nitrogen oxide gases in
time. The addition time of isopropanol is 20
80
°
-
50 min at temperature of 100
°
C. After
-
addition, the temperature is kept at 100
105
°
C for another 10
20 min till no more
-
-
re
uxed and condensed products. Shut down the system of agitation, vacuum, and
condensation, the liquid condensate is separated to two layers and the bottom layer
of acid waste is discarded. The crude product is
fl
rst washed by 3 % Na
2
CO
3
aqueous solution and then washed by deionized water till pH 7. The crude product
is dried and recti
ed under normal pressure. The
final product with a yield of
97.6 % is collected in the cut range of 101
C. The isopropyl nitrate product is
a colorless liquid with relative density of 1.036 and purity of 99.6 % determined by
GC.
In order to study the relationship between the reaction condition and yield, the
writer [
63
,
65
] investigated the effects of urea amount, ammonium nitrate amount,
concentration of nitric acid, the addition time of isopropanol, the feeding system,
and feed types on the yield of isopropyl nitrate. The effect of urea amount on the
yield of isopropyl nitrate is summarized in Table
5.6
, under the reaction condition
102
°
-
