Environmental Engineering Reference
In-Depth Information
40 mm, the detonation velocity is about 8,000 m/s.
In a tube with small diameter, the detonation velocity is approximately 1,500 m/s,
while the detonation velocity exceeds 6,000 m/s in large tubes.
In a tube with diameter of 30
-
5.2.1.3 Preparation of Methyl Nitrate [
1
,
15
,
49
]
In early period, methyl nitrate was prepared by nitration reaction between methanol
and urea nitrate-contained nitric acid or mixed acid of nitric acid and sulphuric acid
(40:60) at 18
40 min [
50
]. The density of nitric acid is 1.4 g/cm
3
without
nitrogen dioxide. After nitration, the products were washed by water to pH 7 and
carefully distilled at 40 or 18
°
C for 20
-
°
C to obtain methyl nitrate. The yield of the nitration
reaction is 45
80 %. The production period of the preparation method is long and
the yield is very low.
People [
51
] prepared methyl nitrate with yield of 85 % through displacement
reaction between nitrate salt and methanol. Methyl nitrate also can be prepared in
acetic acid [
52
]. At 5
-
°
C, methanol was nitrated by nitric acid with methyl nitrate
yield of 72
81 %. However, high concentration of mixed acids would cause serious
heat release in the water-washing step. The other disadvantages include severe
hydrolysis and heavy environmental pollution.
Those preparation methods are very complicated and even the maximum yield is
not more than 81.5 %. In the preparation process, it requires a critical control of
reaction temperature. Otherwise, explosion could happen if temperature is out of
control.
Because of low boiling point and high volatility, methyl nitrate cannot be
washed by hot water. However, cold water also cannot be used in washing step
because of the low viscosity of methyl nitrate. A new preparation method [
46
,
49
]
of methyl nitrate was proposed as the following equation.
-
CON
2
H
4
CH
3
ONO
2
+H
2
O
In industry, in order to obtain pure products, the amount of used methanol
should be controlled to reduce the impurities that might be dissolved into methyl
nitrate, thus that nitric acid could be completely converted to methyl nitrate. The
schematic diagram of methyl nitrate production by continuous nitration is shown in
Fig.
5.1
.
Two normal funnels with a liquid mixture of methanol, water, and urea, referred
as methanol mixture, are separately set at two sides of the set-up. In the middle, it is
equipped with a distillation head, a temperature controller, a condenser, and a
receiver. The procedure of the continuous nitration for methyl nitrate is described as
follows. HNO
3
and distilled water are slowly added to urea in a reaction vessel at
110
CH
3
OH+HNO
3
°
C. The temperature at the position of the distillation head is in the range of
