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OCR for page 213
APPENDIX
Neutralization of Energetic Materials by Hydrolysis
BACKG ROU N D
Because most energetic materials are synthesized in
acidic media (or salts of acids), they are vulnerable to
hydrolysis. The hydrolysis of energetic materials, such
as 2,4,6-trinitrotoluene (TNT), has been of some inter-
est since the mid-1800s (Wilbrand, 1863; Hepp, 1882;
Meyer, 1889~. However, the work has been sporadic
and the results often inconclusive. Limited reviews of
hydrolysis reactions for energetics can be found in the
following general references: Urbanski, 1964, 1965,
1967,1984; Feuer, 1969, 1970. Recently, the Navy has
published a review of alkaline hydrolysis of energetic
materials pertinent to assembled chemical weapons
(ACWs) (Newman, 1999~.
Because open burning or open detonation (OB/OD)
of energetic materials has become increasingly unpopu-
lar, more environmentally acceptable alternative tech-
nologies have been proposed. Base hydrolysis has re-
cently been proposed for the demilitarization and/or
destruction of some types of energetic materials. For
example, several investigators have shown that base
hydrolysis combined with supercritical water oxidation
may be effective for neutralizing pressed explosive
composites containing 1,3,5,7-tetraaza-1,3,5,7-tetra-
nitrocyclooctane (HMX) (Spontarelli et al., 1994;
Flesner et al., 1994; Skidmore et al., 1995; Bishop et
al., 1996~. Cannizzo et al. (1995) have demonstrated
base hydrolysis of a composite propellant containing
HMX, ammonium perchlorate, nitrate esters, and
aluminum powder. Borcherding and his coworkers
(Borcherding and Wolbach, 1995; Borcherding, 1997,
1998) have performed base hydrolysis on at least three
213
types of composite propellant and have claimed, "the
products of the process will be treatable in conventional
waste treatment facilities." In September 1997, a 200
lb/day hydrolysis-treatment facility became operational
and replaced routine OB/OD disposal of waste com-
posite propellant at a site near San Jose, California.
Base hydrolysis decomposes energetic materials to
organic and inorganic salts, soluble organic com-
pounds, and various gases. The base usually attacks all
of the functional groups of the energetic material. In
the past, these reactions were usually conducted at
ambient conditions with dilute concentrations of ener-
getic material and base. Now, however, they are con-
ducted at elevated temperature (between 60°C t140°F]
and 155°C [311 °F]) and often at elevated pressure (up
to 14 atm) in a strong base solution (pH 2 12~. In some
cases, base hydrolysis has been conducted at super-
critical conditions (Larson et al., 1998~. Typically,
higher temperature and pressure are used to increase
the solubility of reactants and to prevent clogging of
the reactor. Sodium hydroxide, potassium hydroxide,
ammonium hydroxide, and sodium carbonate have
been used. These reactions are exothermic and must be
carefully controlled by a method that can immediately
recognize the onset of a thermal excursion and prevent
a runaway exothermic reaction. The reactor must also
be designed to contain the maximum credible explo-
sive event.
Depending on the specific conditions and materials,
several reaction routes are possible that may produce
undesirable precipitates. Energetic materials, such as
nitrate esters, nitroaromatics, and nitramines, usually
decompose to form nitrates, nitrites, ammonia, nitrogen,
OCR for page 214
214
ALTERNATIVE TECHNOLOGIES FOR DEMILITARIZATION OF ASSEMBLED CHEMICAL WEAPONS
hydrogen, organic acids, and formaldehyde. Interme-
diates formed during the hydrolysis of some energetic
materials can provide reaction pathways to other nitro
derivatives and addition products that are still ener-
getic. Current work indicates this occurs preferentially
with aromatic nitro compounds and usually when the
energetic material is in excess.
The solid particles in hydrolysis must be small
enough to expose adequate surface area for expedient
salvation and subsequent reaction. In most of the work
on hydrolysis documented in the literature, the ener-
getic material has been in the form of molding powder,
small pellets, or small chunks from demilitarization
operations. The energetic material has then been dis-
solved, and hydrolysis has been performed well within
solubility limits. For the Assembled Chemical Wean-
ons Assessment (ACWA), the energetic material is still
in ordnance, so the first challenge is to remove it and
reduce it to an appropriate size. The second challenge
is to determine safe operating parameters for hydroly-
sis of a heterogeneous feedstock that may include ener-
getic materials, metals, and contaminants. The third
challenge is for technology providers to design process
equipment and develop process-control protocols that
minimize the accumulation of precipitates and mini-
mize damage in the event of an accident. Finally, the
technology providers must scale up a robust process
that can meet the Army's requirements for various
weapon types and processing rates. The scalability of
operating parameters for base hydrolysis of energetic
materials is not universal and will depend on the spe-
cific chemical munitions being demilitarized.
Base hydrolysis has been proposed by several tech-
nology providers for the destruction of energetic mate-
rials in the ACW inventory. These materials (which
make up fuze components, leads, boosters, bursters,
and rocket motors) include: of 1,3,5-triaza-1,3,5-
trinitrocyclohexane (RDX); Composition B (Comp B)
(a 60/40 gravimetric blend of RDX and TNT plus 1 wt.
percent wax added as a desensitizer); 70/30 tetrytol (a
70/30 gravimetric blend of tetryl and TNT); and M28
double-base propellant (which contains nitrocellulose
ENC] and nitroglycerin ANGUS. These materials fall into
four classes: aromatic nitro compounds (such as TNT),
aromatic nitramines (such as tetryl), heterocyclic
nitramines (such as RDX), and nitrate esters (such as
no and ng).
AROMATIC NITRO COMPOUNDS
Several references can provide a review of the reac-
tivity of aromatic nitro compounds (Feuer, 1969;
Urbanski, 1964, 1984~. It is well documented that het-
erolytic substitutions occur through electrophilic and
nucleophilic attacks from cations and anions, respec-
tively. Homolytic substitutions involve the reaction of
uncharged free radicals. Base hydrolysis is usually a
heterolytic substitution as a result of a nucleophilic attack
of the alkaline anion. However, there is some evidence
that homolytic substitutions can occur simultaneously.
The reactions of aromatic nitro compounds with
bases are often accompanied by intense color changes.
Violet, red, or brown colors can be observed depend-
ing on the alkali system. Much of what is now known
about these reactions has been attributed to Jack-
son (Jackson and Gazzolo, 1900), Meisenheimer
(Meisenheimer, 1902), and Janovsky (Janovsky and
Erb, 1886), whose fundamental work with nitroben-
zene around the turn of the century identified some of
the reversible reactions that form reactive intermedi-
ates. Several possible resonance structures can be quite
energetic, including Jackson-Meisenheimer com-
plexes, Janovsky complexes, and other sigma (~) com-
plexes. Russell and others have demonstrated how nu-
cleophilic attack of a strong base (B-) on aromatic nitro
compounds can simultaneously produce Jackson-
Meisenheimer complexes, a radial anion, and a free
radical (Urbanski, 1964, 1984; Russell et al., 1964~.
Obviously, these species will undergo further reaction
with available substrates. Depending on the reagents
used to generate the anion and the reaction conditions,
several anionic sigma complexes are possible (Strauss,
1970~.
one of the most common aromatic nitro compounds
is TNT (molecular weight 227.13 g/mole, melting point
81°C [178°F]~. TNT is resistant to reaction with acids,
but like all nitro compounds, it reacts easily with bases.
Because the solubility of TNT in water is only about
6.0 x 10-4 M at 25°C (77°F) (DA, 1984), hydrolysis of
TNT has often been performed in an alcohol or a co-
solvent system.
In 1975, Hammersley (1975) published a survey of
alkali reactions with TNT that affirms the conclusions
of Bernasconi (1971) and of Gold and Rochester
(1964~. Hammersly was probably unaware of the work
of Cuta and Beranek (1974~. Many others have also
OCR for page 215
APPENDIX E
performed relevant work in this area (Blake et al., 1966;
Caldin and Long, 1955; Shipp and Kaplan, 1966; Shipp
et al., 1972; Schaal and Lambert, 1962~. Most of the
investigations attempt to identify species that cause
color changes or verify the formation of specific prod-
ucts. However, all of these investigations were per-
formed to study the "pink-water" problems at produc-
tion facilities. Their main focus was to find ways to
precipitate TNT from dilute solution and prevent the
discharge of the pink contaminants to the environment.
Because destruction of TNT was not the goal, the quan-
titative chemical reaction kinetics for the alkaline de-
composition of TNT were not determined.
The base hydrolysis of TNT is probably an ex-
tremely complex series of reactions (Newman, 1999~.
A plausible overall mechanism for the alkaline decom-
position of TNT can be constructed from the work cited
above. The reaction pathways and products differ if
either the base or the TNT is in excess.
With excess base, the general mechanism is:
TNT + RO- ~ TNT
TNT- ~ A + NO2
TNT- ~ B + C + NO2
B ~ NH3 ~ + HCN ~ + HNO2
C ~ D
A ~ E ~
With excess TNT, the general mechanism is:
TNT + RO- ~ TNT
TNT + TNT- ~ JC
TNT + JC- ~ Addition Compounds
where.
TNT
=
MC- =
JC
family of MC- resonance structures
known as an anion of TNT
Jackson-Meisenheimer complex
Janovsky complex
alkali salts of dinitrocresol (these may
precipitate)
B = picric acid
C = isomers of dinitrophenol (these may
precipitate)
alkali salts of phenols
alkali nitronate salts (precipitate)
D =
E
=
iWater on military bases was sometimes contaminated with trace
amounts of TNT, which caused the water to take on a pink color.
215
Quantitative characterizations and prioritizations of
the reaction pathways (or determination of the branch-
ing ratios) have not been completed. However, the cur-
rent level of qualitative understanding is perhaps suffi-
cient to realize that engineering practices can probably
restrict the domain of possible products. The use of
excess strong base is probably the most efficient means
of ensuring that hydrolysis is driven to completion.
However, elevated temperature and pressure must be
carefully monitored to prevent spontaneous and vio-
lent exothermic reactions. A careful review of process-
ing procedures is also warranted to safeguard person-
nel who may have to handle precipitates and other
products of incomplete hydrolysis. This is especially
true during emergency shutdowns and restart proce-
dures. The ACWA technology providers should iden-
tify and demonstrate these engineering practices be-
fore full-scale hydrolysis of TNT is deemed safe and
effective.
AROMATIC NITRAMINES
One of the most common aromatic nitramines is
tetryl (2,4,6-trinitrophenylmethylnitramine) (Urbanski,
1967; DA, 1984; DA, 1991; Kaye end Herman, 1980~.
Tetryl is not very soluble in water. The molecular
weight of tetryl is 287.1 g/mole, and its melting point is
about 130°C (266°F). Tetryl forms a eutectic mix-
ture at 58.3°C (137°F) with 57.9 wt. percent TNT
(Urbanski, 1964~.
Tetryl is resistant to attack by weak acids but will
react with concentrated acid or any alkaline solution.
As early as the 1880s, van Romburgh, Mertens, and
Franchimont established a mechanism for the hydroly-
sis of tetryl (van Romburgh, 1889; Mertens, 1886;
Franchimont and Backer, 1913~. The nitramino group
is hydrolyzed when tetryl is boiled in a dilute solution
(2 wt. percent) of sodium carbonate, sodium hydrox-
ide, or potassium hydroxide. The products are 2,4,6-
trinitrophenol (picric acid), methylamine, and nitrous
acid.
The kinetics for the hydrolysis of tetryl have not
been documented. However, the rate of hydrolysis of
tetryl is slower than that of TNT (Newman, l 999~. The
actual mechanism involved with complete alkaline de-
composition is not known either but is probably very
similar to those that occur in the hydrolysis of TNT. An
OCR for page 216
216
.
ALTERNATIVE TECHNOLOGIES FOR DEMILITARIZATION OF ASSEMBLED CHEMICAL WEAPONS
anion resonance complex should be expected. This an-
ion complex should be the result of a fast intermediate
step, and its formation may complicate the family of
possible hydrolysis products. If the tetryl is in excess,
hydrolysis should yield insoluble Janovsky complexes
and addition products that are potentially energetic. An
excess of strong base should, however, drive hydroly-
sis to completion.
A plausible overall mechanism for the alkaline de-
composition of tetryl can be hypothesized from the
work previously cited for TNT. With excess base, the
mechanism should be:
tetryl + RO- ~ tetryl~
tetryl~ ~ A + NO2-
tetryl~ ~ B + C ~ + NO2-
B ~ NH3 ~ + HCN ~ + HNO2
A ~ D ~
With excess tetryl, the expected mechanism is:
tetryl + RO- ~ tetryl~
tetryl + tetryl~ ~ JC-
tetryl + JC- ~ Addition Compounds
where,
tetryl~ = hypothetical resonance structures that
behave as an anion of tetryl
JC- = Janovsky complexes of tetryl
A = intermediate alkali salts (these may
B =
C
D
precipitate)
. · · .
plcrlc aclcl
methyl amine
alkali nitronate salts (precipitate)
TABLE E-1 Hydrolysis Rates Obtained at Laboratory Scale
More work is necessary to determine the reaction
pathways and the branching ratios. However, as with
TNT hydrolysis, the current level of understanding is
perhaps sufficient to realize that engineering practices
can probably restrict the domain of possible products.
A feasibility study has been performed by the Naval
Air Warfare Center, Weapons Division, at China Lake,
California, to measure the hydrolysis rates with excess
NaOH of TNT and tetryl residue in simulated burster
sections (GA, 1998~. The NaOH concentration was
varied from 12 wt. percent to 20 wt. percent (or from
3.4 M to 6.1 M). The results were reported as linear
hydrolysis rates in millimeters per hour (mm/hr) as a
function of temperature. The linear hydrolysis rate is a
strong function of temperature.
One set of experiments was conducted in laboratory
glassware, and the results are given in Table E- 1. These
data show that the hydrolysis rate for alkaline decom-
position of tetryl increases with temperature and con-
centration of NaOH solution, as expected. However,
the rate is only 16 grams per hour (g/hr) for tetryl in 6.1
M NaOH at 105°C (221°F). In similar tests at 95°C
(203°F) in 3.4 M NaOH, the hydrolysis rate of TNT is
at least 2.7 times faster.
The second set of experiments were performed in a
simulated rotary hydrolyzer (see Chapter 6) in which
the energetic materials were immersed in caustic 66
percent of the total test time. The results for these
bench-scale rotary hydrolyzer tests are shown in Table
E-2. In general, the hydrolysis rates are lower than
those reported in Table E-1 for the laboratory-scale
experiments. It was concluded that the mixing action
for the laboratory-scale experiments was better than for
NaOH Concentration Linear Hydrolysis Gravimetric Hydrolysis
Test# (M) Explosive T (°C) Rate (mm~hr) Rate (g~hr) Comments
2 3.4 tetryl 89 1.5 0.48 vigorous agitation
ga 3.4 tetryl 95 5 to 6 1.6 to 1.9 gentle agitation
1 3.4 tetryl 100 27 8.7 moderate agitation
11 6.1 tetryl 100 34 11 gentle agitation
8 6.1 tetryl 105 50 16 gentle agitation
6a 3.4 TNT 95 5.3 gentle agitation
5 3.4 TNT 95 40 vigorous agitation
aTests 9 and 6 can be compared to assess relative hydrolysis rates for tetryl and TNT in 3.4 M NaOH.
Source: GA, 1998.
OCR for page 217
APPENDIX E
TABLE E-2 Hydrolysis Using a Bench-Scale Rotary Hydrolyzer
217
NaOH Concentration Linear Hydrolysis Gravimetric Hydrolysis
Test# (M) Explosive T (°C) Rate (mimer) Rate (gear) Length of Tube (in)
3 3.4 tetryl 87 2.1 0.68 2
3 3.4 tetryl 87 1.85 0.60 4
3 3.4 tetryl 87 1.82 0.59 4
4 3.4 tetryl 95 7.4 2.4 2
4 3.4 tetryl 95 6 1.9 4
4 3.4 tetryl 95 7-8 2.3-2.6 10
4 3.4 tetryl 95 7-8 2.3-2.6 14
7 6.1 tetryl 101 18 5.8 10
13 6.1 tetryl 101 20 6.5 10
7 6.1 tetryl 101 19 6.1 14
13a 6.1 tetryl 101 20 6.5 14
2a 6.1 TNT 101 54 14
aTests 13 and 12 can be compared to assess relative hydrolysis rates for tetryl and TNT in 6.1 M NaOH.
Source: GA, 1998.
the bench-scale rotary hydrolyzer sections (GA, 1998~.
This result may have ramifications for process design
and scale up. No attempts were made during this feasi-
bility study to identify the hydrolysis products for ei-
ther tetryl or TNT.
In summary, the hydrolysis of tetryl pellets is not
rapid, even in excess base and at reasonably high tem-
peratures. The hydrolysis rate of tetryl is also much
slower than that of TNT, which may prompt technol-
ogy providers to raise the operating temperatures. How-
ever, tetryl will start to decompose to picric acid above
120°C (248°F) (Urbanski, 1967; DA, 1984), so at-
tempts to increase the alkaline decomposition rate by
performing base hydrolysis at temperatures above
120°C should be avoided, because these reactions may
be difficult to control. Because hydrolysis is mass-
transfer limited, reducing the chunk size of the tetryl
feedstock and inducing vigorous agitation in excess
base are probably better ways to increase the rate of
hydrolysis once a threshold temperature and base con-
centration have been achieved. In any case, the tech-
nology providers must identify and demonstrate pro-
cessing conditions for the base hydrolysis of tetryl
before it is deemed safe and effective at full scale.
HETEROCYCLIC NITRAMINES
The most common heterocyclic nitramines are RDX
and HMX (DA, 1984; Kaye and Herman, 1980;
Meyers, 1981; DA, 1996a; DA 1996b). The molecular
weight of RDX is 222.1 g/mole, and its melting point is
about 1 90°C (374°F); the molecular weight of HMX is
~ ____ O
296.2, and it melts at about 277°C (531°F). Because
none of the munitions in the ACW inventory contains
HMX, this discussion focuses on the hydrolysis of
RDX.
RDX is manufactured in the United States by the
Bachmann process, which produces high quality RDX
that may contain from 4 to 17 wt. percent HMX as a
by-product (Urbanski, 1967; DA, 1996a). RDX is prac-
tically insoluble in water.
In 1940, Somlo performed a feasibility study to de-
termine if RDX could be decomposed by alkali hy-
drolysis (Urbanski, 1967; Somlo, 1940~. He reported
that the heterogeneous decomposition of RDX in 1 M
solution of NaOH could be accomplished in about 10
hours at 60°C (140°F). He also reported that increasing
the concentration of the sodium hydroxide solution to
10 M and using intense stirring could reduce the time
to about four hours. The decomposition products were
nitrates, nitrites, organic acids, ammonia, nitrogen,
formaldehyde, and hexamethylenetetramine.
A mechanism for the homogeneous alkaline decom-
position of RDX has been reported by Epstein and
Winkler ~ 1951), Jones ~ 1954), Hoffsommer et al.
(1977), and Croce and Okamoto (1979~. The detailed
mechanism, a series of four reactions, was derived from
base hydrolysis of RDX (3 x 10-5 to 6 x 10-4 M) in
sodium methoxylate (< 0.5 M) between 19°C and 45°C
(66°F and 113°F):
OCR for page 218
218
ALTERNATIVE TECHNOLOGIES FOR DEMILITARIZATION OF ASSEMBLED CHEMICAL WEAPONS
RDX + RO- ~ A + ROH + NO2
A + RO- ~ B- + ROH
B- + RO- ~ C 2- + ROH
r'2- 3D-+NO2
~ -
where R = CH3 W. H. Jones (1954) suggested that A
was the product of HNO2 elimination and might be
1,3,5-triaza-3,5-dinitrocyclohexene-1. He also suggested
structures for the other hypothetical intermediates B.
C, and D, which are all various resonance structures.
Jones also proposed the following equation for the
rate of alkaline decomposition (dx/dt), which depends
on the rate constants for the first and fourth reactions:
dx/dt = k7 ~ a - 3x7 )(b - x ~ + k2 ~ x - x2
where,
a = initial molarity of RO-
b = initial molarity of RDX
kit = the rate constant for the first reaction
k2 = the rate constant for the fourth reaction
x' = molarity of nitrite from the first reaction
x2 = molarity of nitrite from the fourth reaction
Jones also proposed the following expressions to de-
termine the disappearance of RDX and RO-:
- dR/dt = A, R ~ a - 3b + 3R) where R = tRDX]
where Z = tRO-]
-dG/dt = kit ~ (fib-a + ~ J
TABLE E-3 Observed First-Order Rate Constants for
Hydrolysis in Excess NaOH Solution (8.048 x 10-2 M)
at 25 °C
% Completion Time (min)
RDX Concentration
x 1Os (M)
Ax 104
( I! )a
o.o
15.8
17.1
28.9
36.8
40.7
42.1
48.7
52.6
76.3
82.9
alOOb
0.00
7.98
11.88
16.05
19.96
27.91
31.97
35.99
40.05
80.06
99.96
232.80b
7.6
6.4
6.3
5.4
4.8
4.5
4.4
3.9
3.6
1.8
1.3
o.lb
3.5
2.6
3.5
3.8
3.1
2.8
3.1
3.1
3.0
2.9
3.1
3.1
ak1 = 1/t in ([RDX]ol[RDx]t)
bCalculated using the average first order rate constant from this
experiment, kl=3.1.
Source: Hoffsommer et al., 1977.
Epstein and Winkler (1951), Hoffsommer et al.
(1977), and Croce and Okamoto (1979) have offered
and verified a simplified expression for the reaction
kinetics for RDX hydrolysis. The initial reaction is a
proton abstraction from the acidic methylene hydro-
gens located between two adjacent nitramine groups,
whereby nitrous acid is liberated. This initial second-
order reaction is the rate-limiting step. Epstein and
Winkler reported second-order rate constants for base
hydrolysis of RDX in acetone with aoueous NaOH
1
t~ u.o in). fine relative concentrations of the solute and
solvent comprising these solutions were chosen to pre-
vent the precipitation of solids and ensure the miscibil-
ity of the alkaline solution with acetone.
Hoffsommer et al. also reported second-order rate
constants for hydrolysis of RDX (< 2 x 10-4 M) in
NaOH solutions (from 0.02 to 0.5 M) at temperatures
of 25°C,35°C, and 45°C (77°F,95°F, and 113°F). The
reaction kinetics were pseudo first order with excess
hydroxyl ion:
- dERDX]/dt = k2 [NaOH] [RDX] ~ A, [RDX]
The observed first-order rate constants for the aque-
ous, homogeneous, alkaline hydrolysis of RDX in ex-
cess base are provided in Table E-3. Second-order rate
constants were calculated from the first-order rate con-
stants using the expression k2 = kit / [OHS. Second-
order rate constants are given in Table E-4. The forma-
tion rate of nitrite ion during the alkaline hydrolysis of
RDX at 45°C (113°F) is presented in Table E-5. The
variation in hydrolysis products as a function of
hydroxide-ion concentration is given in Table E-6.
Hoffsommer et al. (1977) stated that the formation
of both the formate ion (HCOO-) and formaldehyde
(CH2O) indicated a ring opening of RDX-h-5 by hy-
droxide-ion attack on carbon followed by a series of
TABLE E-4 Second-Order Rate Constants for
Hydrolysis of RDX in NaOH Solutions from 0.02 to
0.25 M
Temperature (°C)
Number of
Kinetic Experiments
k2x 103
( M -I s -I )
25.0
35.0
45.0
6
6
s
3.9+0.2
14+ 1
48+3
Source: Hoffsommer et al., 1977.
OCR for page 219
APPENDIX E
TABLE E-5 Formation of Nitrite Ion during Hydrolysis
of RDX (7.07 x 10-5 M) at 45°C (113°F) with Excess
NaOH Solution (6.82 x 10-2 M)
Time (min)
% RDX
Hydrolysis
+ [NO2-]
x 105 (M)
Mole Ratio
+[NO2-] /-[RDX]
1.38
2.93
4.32
6.17
8.17
41.00
23.4
43.3
56.7
69.8
79.4
100
1.61
3.32
4.59
5.70
6.54
8.35
0.97
1.08
1.14
1.16
1.17
1.18
Source: Hoffsommer et al., 1977.
bond cleavages to form NH3, N2, and N2O. The forma-
tion of some H2 is probably due to OH- attack on CH2O
under Cannizzo's conditions (Cannizzo et al., 1995;
Walker, 1964~. No evidence of the nitrate formation
observed by Somlo (1940) was found.
Dell'Orco investigated the hydrolysis of Comp B (a
blend of RDX and TNT) at the Los Alamos National
Laboratory (LANL) under the Joint Department of
DefenselDepartment of Energy (DOD/DOE) Muni-
tions Technology Program (Dell' Oreo et al., 1995~.
Simple experiments in alkaline decomposition were
performed with 1.5 M NaOH solutions at both labora-
tory and pilot scale. These results are summarized in
Table E-7. Two reaction times were reported. One rep-
resents the amount of time at or above 81°C (178°F);
the other represents the total time from start to finish of
the experiment. Because these experiments were
219
TABLE E-6 Analysis of RDX Hydrolysis Products
with Different Hydroxide Concentrations (Mole ratio
of product formed per RDX hydrolyzed)
[OH-] NO2- N2 NH3 N2O HCOO- CH2O H2
Weak,
0.1 M
Strong,
19 M
1.1 0.12 0.9 1.2
2.1 0.7 1.6 0.4 1.6
0.7 1.1
o
0.2
Source: Hoffsommer et al., 1977.
performed beyond the solubility limits of Comp B. the
hydrolysis rate was slower than expected.
Color changes from orange-red to dark brown and
black were observed during these experiments. A sig-
nificant exotherm occurred at 81 °C (178°F) as the TNT
in the Comp B melted and the rate of reaction increased.
This event was accompanied by vigorous bubbling of
off-gas. The reaction temperature was reported as self-
limited because the boiling point of the solution was
about 91°C (196°F). The reported products of reaction
included precipitates, gases, and liquid-phase species.
Precipitates included unreacted RDX and HMX. The
gas contained nitrous oxide (N2O) and ammonia (NH3~.
The organic products found in the aqueous phase in-
cluded "formate" (presumably the anion and salts or
esters of formic acid) and "hexamine" (apparently hex-
amethylenetetram~ne as reported in Somlo t1940] ). Ion
chromatography results for anionic products from the
hydrolysis of Comp B are given in Table E-8. The table
TABLE E-7 Summary of Alkaline Decomposition Experiments for Comp B Performed by LANL
Scale
[NaOH]
(M)
Time of Reaction
T (°C) (min)
Gravimetric Hydrolysis
% Completion Rate (glhr)
1 g CompB in 1.5 85 15 98.5 3.9
10 ml of NaOH 1.5 33-81 27 98.5 2.2
solutiona
100 g Comp B in 1.5 >81 90 >99.9 66.7
1 liter of NaOH 1.5 33-81 210 >99.9 28.6
solutiona
Two711 g billets 1.5 >81 120 95.7 676
in 14 liters of 1.5 28-83 300 95.7 270
NaOH solutiona
aThe concentration of Comp B in these experiments is calculated to be 0.44 M.
Source: Dell'Orco et al., 1995.
OCR for page 220
220
TABLE E-8
Comp B
ALTERNATIVE TECHNOLOGIES FOR DEMILITARIZATION OF ASSEMBLED CHEMICAL WEAPONS
Anionic Products from the Hydrolysis of
Anion
Shown as a Percentage
of C or N in Comp B
formate
acetate
nitrite
nitrate
30% of C
1.2% of C
25% of N
0.2% of N
Source: Dell'Orco et al., 1995.
TABLE E-9 Product Analysis for Sodium Carbonate
Hydrolysis of HMX Powdera
% Total Carbon
and Nitrogen in HMX
(average of ten experiments)
Carbon in solution
Inorganic carbon
Organic carbon
Carbon-bearing species
Formate (aqueous)
Acetate (aqueous)
Carbon dioxide (gaseous)
lists only the aqueous-phase products and is, there- Carbon monoxide (gaseous)
Carbon
fore, an incomplete material balance. No effort was
made to quantify gas-phase products or to specify
final products.
HMX is present as a contaminant in RDX manufac
tured in the United States. The solubility of HMX in
water is only about 5 ppm at 20°C (68°F). Some inves
tigations have been performed to determine the chemi
cal-reaction kinetics and the products of HMX alkaline
decomposition (Epstein and Winkler, 1951; Croce and
Okamoto, 1979; Spontarelli et al., 1994~. The rate-lim
iting step is a bimolecular elimination reaction produc
ing nitrous acid. The reaction kinetics are second or
der, and according to Epstein and Winkler's data, the
hydrolysis of HMX is more than 300 times slower than
that of RDX at 15.5°C (60°F).
Bishop et al. (1996) have developed a reaction-rate
model for the hydrolysis of HMX. Their second-order
rate constant for the base hydrolysis of HMX in so
dium carbonate (1.01.5 M) was fit to an Arrhenius
equation. The experimentally determined values for
activation energy and pre-exponential factors are given
below in the expression for the reaction-rate constant.
in k = - (92.4 + 0.7 kJ/mol) / RT + 20.8 + 0.8 (in so)
In this equation, the effect of temperature is substan
tial; however, the rate constant (k) is low, and the alka
line decomposition is slow. Bishop et al. claim that this
model can be used in the design of reactors and in scale
up to production.
Because the hydrolysis of HMX is mass-transfer
limited, investigators have resorted to using higher tem
peratures and pressures to increase the reaction rate.
Bishop et al. have recently developed a solid-liquid
mass-transfer model to describe how faster rates can be
achieved for the hydrolysis of HMX by using higher
o.s to as
about 99
44.00
2~.00
0.86
0.74
34.00
Nitrogen-bearing species
Nitrite (aqueous)
Nitrate (aqueous)
Nitrogen (gaseous)
Nitrous oxide (gaseous)
Ammonia (gaseous + aqueous)
20.00
o.os
4.10
ss.oo
2s.00
aThe uncertainty in the values presented is + 15 percent.
Source: Bishop et al., 1998.
temperatures and vigorous agitation (Bishop et al.,
1998~. The hydrolysis products are given in Table E-9.
In summary, the alkaline decomposition of RDX and
HMX is better understood than the alkaline decompo-
sition of either TNT or tetryl. However, there are still
uncertainties regarding the removal and particle-size
reduction of energetic materials in the ACW inventory
that will constitute the feed stream for the hydrolysis
unit. Insufficient size reduction may adversely impact
the effectiveness and scalability of processing param-
eters and may increase safety concerns, such as clog-
ging of the reactor and exothermic runaway at full
scale. Therefore, the ACWA technology providers
must demonstrate processing conditions for realistic
feeds before the alkaline decomposition of RDX, Com-
position B. or HMX can be deemed safe and effective
at full scale.
NITROCELLULOSE AND OTHER NITRATE ESTERS
Information on nitrate esters and their use in various
explosive and propellant applications is available from
several sources (e.g., Miles, 1955; Urbanski, 1965,
1984; Lindner, 1980; DA, 1984; Fedoroff and
Sheffield, 1962, 1972, 1974; Meyers, 1981), many of
OCR for page 221
APPENDIX E
which include substantial information about character-
istics and reactivity. The physical properties of nitrate
esters and their affinity to undergo base hydrolysis or
alkaline decomposition are described briefly below.
Nitrate esters are classified as primary, secondary,
or tertiary, depending on whether they were derived
from primary, secondary, or tertiary alcohols. The com-
plicated base hydrolysis of nitrate esters is now reason-
ably well understood. It involves the cleavage of both
C-O and O-N bonds. The hydrolysis reactions can be
summarized by the following set of expressions
(Urbanski, 1984; Baker and Neale, 1954, 1955; Baker
and Heggs, 1955; Anbar et al., 1954~:
1. Nucleophilic attack on carbon (Sol and SN21:
HO- + RCH2 - O - NO
RCH2 - OH + NO3
2. Nucleophilic attack on nitrogen (SN21:
HO- + RCH2 - O - NO2 ~
tRCH2- O + HONO2 ~ ~ RCH2 - O - H + NO3
3. Nucleophilic attack on oc-hydrogen (Em:
HO- + RCH2 - O - NO
RCH = 0 + NO2- + H2O
4. Nucleophilic attack on ,8-hydrogen (E1 and Em:
HO- + R CH2CH2 - O - NO
RCH=CH2+NO3-+H2O
The hydrolysis of both primary and secondary
mononitrate esters is slow. In general, the hydrolysis of
primary nitrate esters proceeds mostly by substitution
reactions 1 and 2 above. However, the hydrolysis of
secondary nitrate esters is dominated by the elimina-
tion reactions 3 and 4.
NC and NO are the two nitrate esters of greatest con-
cern in the ACWA program. NC is notoriously unstable
at elevated temperatures. At 125°C (257°F), NC de-
composes to CO, CO2, H2O, N2, and NO. At 50°C
(122°F), the rate of decomposition of NC is approxi-
mately 4.5 x 106 wt. percent per hour, increasing by a
factor of about 3.5 with each 10°C (18°F) increase in
temperature. Dry NC burns very rapidly and may deto-
nate when acted upon by a sufficient stimulus if the NC
is present in large quantities or if it is confined. NC is a
dangerous material to handle dry because of its sensi-
tivity to friction, static electricity, impact, and heat. The
higher the nitrogen content, the more sensitive NC
tends to be. Therefore, NC is always shipped wetted
221
with water or alcohol. However, even NC with 40 per-
cent (vol.) water can detonate if it is confined and acted
upon by a sufficient stimulus (Lindner, 1980~.
NC is not a single homogeneous product. Rather, it
is a family of very similar compounds containing
mono-, di-, and tri-nitrocellulose. The molecular
weight of NC depends on the nitrogen content and can
be calculated using the following expression.
molecular weight of NC = 324.2 + t% N / 14.14] 270
Military grades of NC contain more than 12 percent
N. Four grades of NC are specified for military use;
however, it is often blended to meet the performance
requirements of specific weapons. The cast double-
base propellant grain, M28, specified for the M55
rocket contains both NC and NO. However, the actual
nitrogen content for the NC is not specified (DA, 1966~.
NC is soluble in acetone but insoluble in water. The
higher the nitrogen content, the less soluble NC is in
ether-alcohol mixtures (Sax and Lewis, 1987), and al-
kaline solutions. Therefore, the residence time required
for alkaline decomposition of NC (14 percent N) is
expected to be longer than for NC (12 percent N). Be-
cause NC is more soluble in ammonia than in aqueous
alkaline solution, some researchers recommend ammo-
nia hydrolysis, or "ammonolysis," for destroying NC
(Cannizzo et al., 1995; Morgan et al., 1994; Melvin,
1997; GA, 1997~. The alkaline decomposition of NC in
aqueous NaOH solution is mass-transfer limited.
Kenyon and Gray (1936) performed a quantitative
study of the alkaline decomposition of NC in which
they examined the time necessary for dry NC fibers to
disappear in NaOH solutions. Although their time mea-
surement technique is not extremely reliable, it does
indicate a relative order of magnitude required to per-
form the operation on a laboratory scale. They evalu-
ated the effect of base concentration and temperature
on hydrolysis rate. Their data set for the alkaline de-
composition of NC at 30°C (86°F) is given in Table E-10
and at 60°C (140°F) in Table E-ll. They concluded
that alkaline decomposition of NC proceeds faster at
higher temperature and in stronger base. They also ob-
served that small amounts of carbon dioxide were prod-
ucts of decomposition and that large amounts of the
nitrates were reduced to nitrites. An average of about
66.6 percent of the nitrogen in NC was reduced to
OCR for page 222
222
ALTERNATIVE TECHNOLOGIES FOR DEMILITARIZATION OF ASSEMBLED CHEMICAL WEAPONS
TABLE E-10 Alkaline Decomposition of NC (12.2% N) at 30°C (86°F)
Volume of
Mass of NaOH Solution NaOH Concentration Time Required for
NC (g) (cc) (%) Decomposition (hrs)
10 100 20 (or 6.09 M) 2.58
10 200 10 (or 2.77 M) 11.13
10 400 5 (or 1.32 M) 23.33
10 800 2.5 (or O.64M) 170.90
10 2000 1.0 (or O.25 M) 245.00
Source: Kenyon and Gray, 1936.
either nitrates or nitrites during alkaline decomposition
at 30°C (86°F) and about 71 percent at 60°C (140°F).
NG is a pale yellow viscous liquid, also known as
glyceryl trinitrate or trinitroglycerin, with a molecular
weight of 227.1 g/mole. It is soluble in almost all or-
gan~c solvents and is sufficiently soluble in water (0.18 g/
100 g H2O at 20°C [68°F]) to cause a contamination
problem in a process waste stream. When acid free,
NG is stable, but it is very sensitive to impact. NG de-
composes at temperatures above 60°C (140°F) to form
nitric oxides that catalyze further decomposition. Mois-
ture increases the rate of decomposition. Unconfined
NG will burn without transitioning to a detonation;
however, it will detonate if confined.
Even though it is well known that NC and NG can
be destroyed by alkaline decomposition in the labora-
tory, the application of this method to actual propellant
formulations will have to be tested further to determine
its feasibility as a demilitarization technique. NG
readily plasticizes NC to form a gel that will solidify
and provide useful mechanical properties, making it
attractive as a rocket propellant. Unfortunately, this
plasticizing effect makes alkaline decomposition of
double-base propellants much more difficult than
merely performing base hydrolysis of its components.
Preliminary experiments indicate that base hydrolysis
of gun propellants under normal conditions (at stan-
dard temperature and pressure) requires several hours
for decomposition. During hydrolysis of a double-base
propellant, NG can be expected to be hydrolyzed first
via extraction from the NC. However, the conditions
that favor this separation are severe. The double-base
propellant must be in small pieces, and the temperature
and/or pressure must be relatively high.
Bunte et al. (1977) have demonstrated a more rapid
chemical destruction of double-base propellants using
high-pressure alkaline hydrolysis. To destroy a large
quantity of obsolete ordnance in Germany, researchers
were asked to identify an "environmentally friendly"
technology. Bunte, Krause, and Hirth have advocated
alkaline hydrolysis at about 150°C (302°F) and 20 aim,
which they claim results in the same hydrolysate prod-
ucts as under normal conditions but 8 to 10 times faster.
The five actual gun and rocket propellant formulations
used in their experiments are presented in Table E-12
as Pi through P5.
A 180-cm3 autoclave (OD = 70 mm, ID = 48 mm)
batch reactor was used to assess the products of alka-
line decomposition of these propellants. The experi-
mental conditions included a propellant-to-water
weight ratio of 1 to 10, and a propellant-to-NaOH
weight ratio of 2.3 to 1. About 120 ml of this reaction
TABLE E-11 Alkaline Decomposition of NC (12.2% N) at 60°C (140°F)
Volume of
Mass of NaOH Solution NaOH Concentration Time Required for
NC (g) (cc) (%) Decomposition (hrs)
10 100 20 (or 6.09 M) 0.05
10 200 10 (or 2.77 M) 0.23
10 400 5 (or 1.32 M) 0.83
10 800 2.5 (or O.64M) 8.00
Source: Kenyon and Gray, 1936.
OCR for page 223
APPENDIX E
TABLE E-12
German Propellant Formulations Used in Pressured Alkaline Decomposition Experiments
NameP1 (% by wt)P2 (% by wt) P3 (% by wt)P4 (% by wt) P5 (% by wt)
NC9780 57.557 56
NG 14 26.728 26
DNT 2 8.511 9
Centralite 2 2.93 2.9
DPA2
Graphite11
Potassium salt 1
Lead 1.4
Dibutylphthalate 4.5
Vaseline 11 1
NC = nitrocellulose (% N not given)
NG = nitroglycerin
DNT = 2,4-dinitrotoluene
DPA = diphenylamine
Source: Bunte et al., 1997.
mixture was put into the autoclave, and the autoclave
was evacuated and then filled with helium to a pressure
of about 20 atm. The reactor was heated at 10°C/m~n to
150°C (302°F) (15 minutes), and this temperature was
held for one hour. The hydrolysis is exotherm~c, and
small temperature increases (on the order of about 10°C
[18°F] ) were reported.
Because NC is the major component of the P1
through P5 propellants, the products of NC decompo-
sition were identified. The main products are nitrite and
nitrate in the aqueous phase, along with small-chain
organic acids (Urbanski, 1984; Kenyon and Gray,
1936; Bunte et al., 1997~. Using ion-exclusion chroma-
tography, the small-chain organic acids were identified
223
as malonic acid. succinic acid. clutaric acid. formic
, ,
acid, acetic acid, and propionic acid. These prod-
ucts are all biodegradable, and Bunte et al. recom-
mend treating them with a two-step bioremediation
operation, anoxic denitrification and normal aerobic
treatment.
The propellant samples were originally in the form
of sticks and cylinders that were ground down to a par-
ticle size of about 1-5 mm. The results for the decom-
position of the propellant P2 are summarized in Fig-
ures E- 1 through E-4. The results for all five propellants
are generalized in Table E- 13.
As Figure E-1 shows, more than 50 wt. percent of
the nitrogen in P2 is decomposed to gaseous products,
TABLE E-13 Results for the Pressured Alkaline Decomposition of Propellants P1-P5
% of the Total Carbon and Nitrogen in the Propellant
Residue P1 P2 P3 P4 P5
Solid residue
containing DPA, graphite,
centralite, lead oxide,
dibutylphth al ate
Liquid residue
containing NO2, NO3,
DNT emulsion
DPA emulsion,
COD, HCO3
Gaseous residue
containing N2, N2O,
NO, CO2, CO, CHn
2-3 3-12 10
5-16 10
40-70
20-50
Source: Bunte et al., 1997.
OCR for page 224
224
100 1'
80 ~
cow
a'
a' 60
AIL
-
40
20
o
ALTERNATIVE TECHNOLOGIES FOR DEMILITARIZATION OF ASSEMBLED CHEMICAL WEAPONS
AIL
/ /, i
NO3 Ngas N2 N2O NOx N sum
N res N lie NO2
FIGURE E-l Conversion of nitrogen (N) during pressurized alkaline decomposition of propellant P2.
which include mostly elemental nitrogen and nitrous
oxide. The amount of NOX is less than 10 wt. percent.
More than 40 wt. percent of the nitrogen in P2 is de-
composed to liquid products, which include nitrates and
nitrites. Less than 5 wt. percent of the nitrogen in P2 is
decomposed to a solid residue. The material balance
for the carbon in P2 is uncertain, as shown in Figure E-2.
The carbon content of the P2 propellant is transformed
into about 8 wt. percent CO2, less than 1 wt. percent
CO, and less than 0.1 wt. percent, of methane. Depend-
ing on the specific additives in the propellant, between
6 and 10 wt. percent of the carbon can be found in the
solid residue. The main products in the aqueous solu-
tion are carboxylic acids, carbonates, and bicarbonates.
The chemical oxygen demand (COD) in the liquid
phase is between 50 and 60 percent carbon. This is the
so - /
70
60
50
a)
c'
a)
ILL
40
30
20
10
O-
measure of the amount of oxidizable compounds
present in water. Because this value does not differen-
tiate stable from unstable organic matter, it does not
necessarily correlate with the biochemical oxygen-de-
mand value.
The formation of gaseous products is strongly influ-
enced by reaction conditions. The quantity of gaseous
products can be reduced if stronger alkaline solutions
are used (e.g., propellant-to-NaOH weight ratio of 1: 1~.
Figures E-3 and E-4 show the conversion results for
nitrogen and carbon, respectively, for the alkaline de
composition of propellant P5 using propellant-to-
NaOH weight ratios of 2.3:1 (weaker alkaline solution)
and 1:1 (stronger alkaline solution). In Figure E-3, the
gaseous products are reduced from about 20.3 wt. per-
cent to 2.6 wt. percent by going to the stronger alkaline
~ 7
LO A/ I mu/ I ~ //'l k ~// '~714Y
ores
Ccod
C gas CO co2 CH n
FIGURE E-2 Conversion of carbon (C) during pressurized alkaline decomposition of propellant P2.
C sum
OCR for page 225
APPENDIX E
225
100 ~
80 ~
60-
c'
a'
ray 40
20
O- ~ ~
N res N liq NO2 NO 3
1:1
2.3:1
,~
NgaS N 2 N2 o NOx N sum
FIGURE E-3 Conversion of nitrogen (N) during pressurized alkaline decomposition of propellant PS under different alkaline
conditions.
solution. NOX formation is also virtually eliminated. In
Figure E-4, the CO2 has been reduced from 4.5 wt. per-
cent to less than 0.1 wt. percent. The carbon content in
the solid residue is also reduced from 21.9 percent to
9.4 wt. percent. The COD value increased from 71 per-
cent to 87 wt. percent, indicating more oxidizable com-
ponents in the liquid phase.
The products of pressurized alkaline hydrolysis for
propellants P1-P5 depend on the additives in the com-
positions. Components that do not completely react,
such as diphenylamine (DPA) and centralite, will pre-
cipitate as solid residue. However, some DPA appears
as an emulsion in the liquid phase. The most problem-
atic component in this evaluation is dinitrotoluene
100 ~
80 ~
~ 60
rip 40
20
(DNT). In additional experiments performed with pure
2,4-DNT, only 7 percent of the nitrogen was found as
nitrite in the liquid phase (Bunte et al., 1997), and none
was found in the solid residue. Therefore, it is believed
that DNT is not completely converted and may still be
present as an emulsion in the aqueous phase. Emulsi-
fied components, such as DNT and DPA, must be re-
moved before aerobic bioremediation can proceed.
These results have been described in substantial de
tail because they impact the proposed approaches for
demilitarizing assembled chemical weapons. Some
technology providers propose using base hydrolysis of
all of the energetic materials from ACW ordnance in a
single batch reactor during a demilitarization campaign
1:1
2.3:1
,: , , , , , ~ , ' , ' ,
Ores C ~ jq COD HCO3
Cgas CO CO2 CH n Csum
FIGURE E-4 Conversion of carbon (C) during pressurized alkaline decomposition of propellant PS under different alkaline
conditions.
OCR for page 226
226
ALTERNATIVE TECHNOLOGIES FOR DEMILITARIZATION OF ASSEMBLED CHEMICAL WEAPONS
(Lockheed Martin, 1997; Parsons, 1997~. Because the
M55 rockets contain both aromatic nitro compounds
and nitrate esters, simultaneous hydrolysis on bursters
and rocket motors could be problematic. First, the dis-
sociated components of the M28 propellant could react
with TNT intermediates during hydrolysis. Second, the
decomposition of emulsified components or interme-
diates might require very severe operating conditions
or extremely long residence times.
Every M55 rocket contains about 19.3 pounds of
M28 propellant. Assuming that access to the grain is
adequate and that particle size reduction is sufficient to
obtain hydrolysis results similar to those presented for
propellant P5, the NC and NG will be hydrolyzed.
However, the remaining components will either be pre-
cipitates or will exist as an emulsion in the aqueous or
liquid phase.
Lead stearate, an additive in M28 propellant, is in-
soluble in water at ambient temperature but is soluble
in hot alcohol (Sax and Lewis, 1987~. Hence, the com-
mittee is concerned that it may dissolve in hot alkaline
solution, in which case the lead cations could combine
with other anionic substrates in a batch reactor and pre-
cipitate out sensitive compounds. This possibility is
supported by the results for propellant P3. For example,
picric acid will be formed during hydrolysis of the TNT
or tetryl contained in the M55 rocket bursters. If burst-
ers and propellant are hydrolyzed simultaneously, lead
from the propellant could either precipitate out or form
lead picrate. In the hydrated form, lead picrate is not
particularly sensitive. However, enough heat could be
produced from this exothermic process to heat and de-
hydrate the lead picrate deposited on vessel walls. As
indicated in the section on TNT hydrolysis, dry lead
picrate is an extremely sensitive explosive and is very
dangerous to handle. Therefore, the committee believes
that, to avoid forming sensitive compounds such as lead
picrate, hydrolysis of bursters and propellant should be
performed in separate vessels unless further testing
demonstrates the process is safe.
It is uncertain whether slightly soluble components
are eventually decomposed or emulsified if they are
allowed to undergo prolonged base hydrolysis. Bunte
et al.(l997) report that alkaline hydrolysis of centralite,
DPA, DNT, and TNT may require supercritical hy-
drolysis and oxidation (374°C t705°F] and 218 aim
[3204 psi]) to be completely decomposed. In any event,
the technology providers will have to demonstrate that
the hydrolysate product from base hydrolysis of ener-
getic materials is an appropriate feedstock for the next
unit operation. Some of these emulsions, such as TNT.
tetryl, and 2-nitrodiphenylamine, may not be good can
didates for biotreatment.
SU M MARY
This review of the hydrolysis of energetic materials
important to the ACWA program, based on available
literature, shows that the base hydrolysis of energetic
materials extracted from obsolete ordnance is not a
mature technology. There is relatively little experience
with the alkaline decomposition of ACWA-specific
energetic materials (compared to experience with
chemical agents). Most of the base hydrolysis described
in the literature on other energetic materials was con-
ducted in dilute solutions and within solubility limits.
Under these conditions, several undesirable products
and precipitates can result. Data in the literature rel-
evant to the hydrolysis of energetic materials from as-
sembled chemical weapons indicates that hydrolysis is
relatively slow unless the reaction conditions are se-
vere (elevated temperature, pressure, and pH) because
these materials are not very soluble in aqueous systems
and the hydrolysis of solids is mass-transfer limited.
To overcome this problem, investigators have resorted
to using strong alkaline solutions, high temperatures,
and even high pressures. In general, the relative hy-
drolysis rates of the energetic materials of interest to
the ACWA program are expected to be (from faster to
slower):
NG>TNT>tetryl2RDX>HMX>NC
One of the most important unresolved issues is that
the family of products is not understood well enough to
support simultaneous hydrolysis of different kinds of
energetic materials in the same batch reactor. This tech-
nique should be disallowed until there is substantial
evidence that intermediates from the hydrolysis of aro-
matic nitro compounds will not combine with M28 pro-
pellant additives or fuze components to form extremely
sensitive explosives or other dangerous precipitates. An
associated concern is that the conditions under which
aromatic nitro compounds, such as TNT or picric
OCR for page 227
APPENDIX E
acid, will emulsify in the aqueous phase and not be
completely hydrolyzed are not understood. Any unit
operation that immediately follows hydrolysis of ener-
getic material should be designed to accept emulsified
aromatic nitro compounds, such as TNT or picric acid,
as contaminants in the aqueous feed stream.
The principal problem for ACWA technology pro-
viders is to develop and demonstrate a practical produc-
tion process based on previously unrelated chem~cal-
engineering unit operations and emerging technologies
to satisfy destruction efficiency requirements. These
chem~cal-engineering unit operations are: (1) section-
ing of munitions to gain access to the energetic materi-
als, (2) reducing the size of energetic materials ex-
tracted from ordnance sections to expedite salvation
and reaction, and (3) decomposing a heterogeneous
feed stream consisting of energetic materials, metal,
and contaminants via alkaline decomposition. The hy-
drolysate produced must be an appropriate feed stream
for the next unit operation, which may be another
emerging technology (supercritical water oxidation and
biotreatment have been proposed).
An associated problem for the ACWA technology
providers is to develop sound engineering and mana-
gerial practices in the event of incomplete alkaline
decomposition of the heterogeneous feed stream.
Products and precipitates of incomplete hydrolysis of
energetic materials can still be energetic and toxic, and
some emergency shutdowns during processing are
likely considering the overall complexity of the process.
The current level of understanding is, perhaps, suffi-
cient to indicate that engineering practices can prob-
ably restrict the domain of possible reaction products.
The use of strong base is probably the most efficient
way to ensure that hydrolysis is driven to completion.
Ammonia hydrolysis for the alkaline decomposition of
some energetic materials could be considered. This
would decrease the solubility problem and minimize
the need for severe reaction conditions to increase
throughput rates.
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of inorganic oxyacids. Part I. The mechanism of hydrolysis of
alkyl esters, i8O being used as a tracer, and its relation to other
reactions in alkaline media. Journal of the Chemical Society,
1954, Vol. III: 3603-3611.
227
Baker, J.W., and T.G. Heggs. 1955. Hydrolytic decomposition of
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Representative terms from entire chapter:
alkaline decomposition
