Environmental Engineering Reference
In-Depth Information
in the production of BDNPF/A from the early-produced DNPOH, such as the low
product purity, short storage and service periods, aging, etc. It is necessary to
further optimize the DNPOH production process.
In the early oxidation nitration preparation of DNPOH, the yield is relatively low
(59
cation, there is formaldehyde conden-
sation reaction and other serious problems. Jeong et al. [ 63 ] modi
63 %), the product needs further puri
-
ed the oxidation
nitration process to optimize the oxidation nitration conditions of silver nitrate, in
which aqueous formaldehyde solution (mass fraction of 35 %) was used for hy-
droxymethylation and its reaction conditions were optimized, and a yellow solid
DNPOH was obtained after extraction with methylene chloride and distillation. The
average yield of DNPOH was more than 90 % and the mass fraction was more than
97 %. Based on these results, Grakauskas et al. [ 40
42 , 65 ] used potassium ferri-
cyanide as catalyst and potassium persulfate as oxidant to synthesize DNPOH. In
this method, with potassium(sodium) ferricyanide and over potassium(sodium)
persulfate, nitrite substitution reaction of nitroethane with sodium nitrite occurred,
and then further reacted with formaldehyde under basic conditions, and
-
finally
DNPOH was extracted out with ethyl acetate under acidic conditions. Product was
obtained through potassium distillation. The reaction mechanism is:
K 3 Fe(CN) 6 .Na 2 S 4 O 8
NaNO 2
CH 3 CH(NO 2 ) 2
CH 3 CH 2 NO 2
HCHO.NaOH
H + ,CH 3 COOCH 2 CH 3 extraction
CH 3 C(NO 2 ) 2 CH 2 OH
It was found that polar organic solvents, as the extraction agents, could be
selected to extract DNPOH from the aqueous phase as shown in Table 4.8 .
According to Table 4.8 , the choice of ethyl acetate, butyl acetate, methyl tert-butyl
ether, cyclohexane and other polar reagents are bene
cial to extraction. The con-
centrated crude product from the extraction agent does not need further puri
cation,
and the purity can be up to 98
99 % that can be directly used in the synthesis of
BDNPF/A. In this reaction, the key factors to affect the product yield are pH of the
reaction mixture and the oxidation time. Rely on the
-
fine controlling on these key
factors, the
final yield of DNPOH can be up to 80 %. Comparison of impacts of
several different process to produce DNPOH on environment is shown in Table 4.9 .
In Table 4.9 , the inexpensive sodium persulfate is used as oxidant, and potassium
ferricyanide as catalyst. The cost is relatively low. Compared to Ter Meer method,
it has limited environmental pollution. Compared with the earlier process, the
improved DNPOH production,
de
company, has lower cost with small environmental pollution, which is suitable for
industrial production.
Although ferricyanide method to produce DNPOH has many advantages, a large
amount of oxidants is used in this process, and a large amounts of waste is pro-
duced, in which contains a large amount of salt and pollution on environment, and
the treatment costs is increased.
ferricyanide method developed in polysul
 
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