Environmental Engineering Reference
In-Depth Information
solution will be distilled to obtain ethyl nitrate [
54
]. If amine oxide is in the reaction
system, ethanol will be oxidized to aldehyde. The nitration could be in
fl
uenced by
quite a bit nitrogen oxide in the acids.
The writer [
53
] invented the approach of continuous nitration of nitric acid vapor
to prepare ethyl nitrate. The solution of alcohol and nitric acid was added dropwise
into a reactor, in which a protective agent of carbonyl groups was contained. The
products were continuously distilled out of the reaction system during the process
of nitration reaction. Thus, the removal of ethyl nitrate makes the concentration of
products low, favoring the forward reaction and increasing the yield of nitration.
Meanwhile, because the retention time of nitrate esters in the thermal reactor is
shortened, the amount of nitrous acid, as well as intermediates, is reduced,
improving the safety of the production process. The reaction process can be
described by the following equation.
CH
3
CH
2
OH
þ
HNO
3
!
CH
3
CH
2
ONO
2
þ
H
2
O
Two normal funnels with an alcohol/protective agent solution and 68 % nitric
acid solution, respectively, with the same weight are separately set at two sides of a
reactor, in which zeolites are added. In the middle, it is equipped with a distillation
head, a temperature controller, a condenser, and a receiver.
The nitrated agent is composed of 75
10 %
protective agent. The protective agent consists of urea, cyanoguanidine, and
melamine.
The preparation procedure of ethyl nitrate is described below. A certain amount
of the protective agent aqueous solution is added into the reactor. A quantity of
HNO
3
is slowly added into the solution. The temperature of an oil bath is set at
130
90 % HNO
3
,5
15 % H
2
O, and 5
-
-
-
C and the temperature of the distillation head is controlled in a reasonable
range. When the protective agent is dissolved and the solution is boiled at the
temperature of set point, the vapor of nitric acid is full of the reaction. Anhydrous
ethanol and nitric acid solution are dropwisely added into the reactor with a certain
adding rate. Oily drops can be observed in the condenser. The solution in the
receiver starts to be layered. Keeping the reaction temperature and the reactants
adding rate makes the reaction steadily running.
After addition of reactants, the temperature of the oil bath is kept at 130
°
C for
another 20 min to ensure that the products are completely distilled out of the
reactor. Obvious layers can be seen in the receiver. The product of nitrate ester is in
the bottom layer. The crude product would be washed by water to pH 7. Sodium
carbonate solution would be then used to continuously wash the product to pH 7.2
°
-
7.5. The crude nitrate ester product would be stored with the desiccant of mag-
nesium sulfate. The product could be added into recti
cation system with zeolites to
obtain highly pure nitrate esters.
The above-described process has changed the traditional preparation method to
produce ethyl nitrate. The advantages of this method, including carbonyl protection,
effective vapor usage in nitration, quick removal of product out of the reactor, and
controllable feedstock addition rate of feedstock and reaction rate, reduce the
