Synergistic Catalytic Effect of a Series of Energetic Coordination Compounds based on Tetrazole-1-acetic Acid on Thermal Decomposition of HMX

Article abstract of DOI:10.1002/zaac.201700088

A series of energetic coordination compounds [Co(tza)₂}_n (1), [Bi(tza)₃]_n (2), {[Cu₄(tza)₆(OH)₂]·4H₂O}_n (3), [Mn(tza)₂]_n (4), {[Bi(tza)(C₂O₄)(H₂O)]·H₂O}_n (5) and [Fe₃O(tza)₆(H₂O)₃]NO₃ (6) based on tetrazole-1-acetic acid (Htza) were synthesized though environmentally friendly methods. The coordination compounds were characterized by elemental analyses, IR spectroscopy, single-crystal and powder X-ray diffraction (PXRD), thermogravimetric analyses (TG), and differential scanning calorimetry (DSC). Their catalytic performances and the synergetic catalytic effects between 1 and 2, 3 and 4, 5 and 6 on the thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) were all investigated by DSC. The results revealed that compounds 1–6 are thermally stable energetic compounds and they all exhibit high catalytic action for HMX thermal decomposition. The catalytic effects of the compounds on HMX thermal decomposition are closely related to the oxides, which come from the decomposition of the compounds, but have no positive relationships with the heat releases of the compounds themselves. Moreover, the synergetic catalytic effects between 1 and 2, 3 and 4, 5 and 6 were observed. Their mixtures at different mass ratio have different synergetic catalytic effects, and the sequence of the biggest synergetic index (SI) in each system is copper-manganese system (compounds 3 and 4) > iron-bismuth system (compounds 5 and 6) > cobalt-bismuth system (compounds 1 and 2), indicating that the synergistic catalytic effects are mainly related to the combination and the proportion of the compounds.

Full text of DOI:10.1002/zaac.201700088

Journal of Inorganic and General Chemistry
DOI: 10.1002/zaac.201700088
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Synergistic Catalytic Effect of a Series of Energetic Coordination
Compounds based on Tetrazole-1-acetic Acid on Thermal
Decomposition of HMX
Yuan-Yuan Qu,[a] Zhi-Xian Wei,*[b] Li Kang,[a] Fei Xie,[a] He-Dan Zhang,[b] and Pan Yue[b]
Abstract. A series of energetic coordination compounds [Co(tza)2}n decomposition. The catalytic effects of the compounds on HMX ther-
(1), [Bi(tza)3]n (2), {[Cu4(tza)6(OH)2]·4H2O}n (3), [Mn(tza)2]n (4), mal decomposition are closely related to the oxides, which come from
{[Bi(tza)(C2O4)(H2O)]·H2O}n (5) and [Fe3O(tza)6(H2O)3]NO3 (6) the decomposition of the compounds, but have no positive relation-
based on tetrazole-1-acetic acid (Htza) were synthesized though envi-
ships with the heat releases of the compounds themselves. Moreover,
ronmentally friendly methods. The coordination compounds were the synergetic catalytic effects between 1 and 2, 3 and 4, 5 and 6
characterized by elemental analyses, IR spectroscopy, single-crystal were observed. Their mixtures at different mass ratio have different
and powder X-ray diffraction (PXRD), thermogravimetric analyses
(TG), and differential scanning calorimetry (DSC). Their catalytic per-
formances and the synergetic catalytic effects between 1 and 2, 3 and
synergetic catalytic effects, and the sequence of the biggest synergetic
index (SI) in each system is copper-manganese system (compounds 3
and 4) Ͼ iron-bismuth system (compounds 5 and 6) Ͼ cobalt-bismuth
4, 5 and 6 on the thermal decomposition of octahydro-1,3,5,7-tetra- system (compounds 1 and 2), indicating that the synergistic catalytic
nitro-1,3,5,7-tetrazocine (HMX) were all investigated by DSC. The effects are mainly related to the combination and the proportion of the
results revealed that compounds 1–6 are thermally stable energetic
compounds.
compounds and they all exhibit high catalytic action for HMX thermal
position, however, rare have distinct catalytic effects on the
thermal decomposition of HMX [the oxidizer in nitrate ester
plasticized polyether (NEPE) solid propellant]. Hence, it is
worthwhile to investigate the high efficient catalysts for HMX
thermal decomposition, and one can choose excellent combus-
tion catalysts for NEPE propellant further.
Single metal compounds always show limit catalytic effects
for the complex propellant components in most cases, and
mixed/compositive/polynuclear metal energetic compounds as
combustion catalysts should be researched and chose.[13–15]
The mixed/compositive/polynuclear metal energetic com-
pounds can produce multiple or more metal or metal oxide
mixtures on the propellants surface than single metal com-
pounds at the molecule level and then can offer a wider range
of selective or synergetic catalytic effects.[16] Therefore, using
the synergies between different metal compounds to improve
the combustion properties of solid propellants should be
studied as an important issue. But, to our best knowledge, ra-
rely studies in this part have been reported so far.
Tetrazole-1-acetic (Htza), an important energetic ligand, has
been widely used in the synthesis of energetic compounds such
as [Pb(tza)2]n,[17] [Bi(tza)3]n,[18] {[FeIIFeIII3O(tza)6(H2O)3]·
3NO3·5H2O}n,[19] [M(tza)2] (M = Zn, Cd, Mn),[20] and a series
of CuII coordination compounds.[21] However, their catalytic
effect on the thermal decomposition of HMX have not been
studied so far. As environmental friendly metal ions, the oxides
or compounds of bismuth, manganese, iron, and copper, such
as Bi2WO6,[15] [Mn(BTA)(phen)2·5H2O]n,[22] Cu(Hatrz)(pda)
(H2O)·H2O, CuICuII(atrz)(pda)(H2O)[23] and some ferrocenyl
compounds,[10] have been synthesized and used to catalyze the
Introduction
Ammonium perchlorate (AP), cyclotrimethylene tri-
nitramine (RDX), and cyclotetramethylene tetranitramine
(HMX) are the main ingredients in solid propellants, and hence
their thermal decomposition characteristics directly influence
the combustion performance of the solid propellants.[1–4] Ener-
getic coordination compounds used as the catalysts/additives
to the propellants have attracted tremendous interests for such
compounds not only contain more N=N or C=N groups, which
hold a higher positive enthalpy formation but also provide
fresh metal or metal oxide at the molecule level on the propel-
lant surface, which could improve combustion performance
when the compounds are used as the catalysts/additives to the
propellants.[5] Hence, a lot of energetic metal compounds
have been researched recently as catalysts for the thermal
decomposition of AP, RDX, and HMX, such as a series of
ferrocenyl compounds,[6–10] two energetic complexes,
Co(TO)2(DNBA)2(H2O)2 and Cu(TZA)(DNBA), incorporating
3,5-dinitrobenzoic acid and azole ligands,[11] [Mn(BTO)
(H2O)2]n [BTO = 1H,1ЈH-[5,5Ј-bitetrazole]-1,1Ј-bis(olate)].[12]
Among those energetic metal compounds, most of them show
excellent catalytic activities for AP and RDX thermal decom-
* Dr. Z.-X. Wei
E-Mail: zx_wei@126.com
[a] Department of Chemistry
School of Science
3 Xueyuan Road
Taiyuan, Shanxi, 030051, P. R. China
[b] Department of Safety Science and Engineering
Chemical Engineering and Environment Institute
3 Xueyuan Road
Taiyuan, Shanxi, 030051, P. R. China
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thermal decomposition of HMX and most of them exhibit good
catalytic effects.
Considering the above research and the environmental pro-
tection, a series of environmental friendly energetic com-
pounds based on Htza were synthesized though environmen-
tally friendly methods and their catalytic effects on HMX
thermal decomposition were all investigated. The com-
pounds [Co(tza)2]n (1) and [Bi(tza)3]n (2) were obtained suc-
cessively in one pot, when Co(NO3)2 and Bi(NO3)3 were
added to the solution of Htza in order to obtain heteronuclear
compounds. Compounds {[Bi(tza)(C2O4)(H2O)]·H2O}n (5)
and [Fe3O(tza)6(H2O)3]NO3 (6) were also continuously syn-
thesized in the similar way except that the reactants were dif-
ferent substances. Herein, it is noted that the compounds
{[Cu4(tza)6(OH)2]·4H2O}n (3) and [Mn(tza)2]n (4) could not
be obtained in the similar way as described above, hence, they
were synthesized separately and constituted a catalytic system
in order to study their synergistic catalytic activity. In a word,
the compounds 1 and 2, 3 and 4, 5 and 6 were divided into
three different synergistic catalytic systems, respectively. Their
synergistic catalytic effects on the thermal decomposition of
HMX were also studied in this paper. The results would pro-
vide the basic data for finding the most efficient combustion
catalysts for NEPE propellant.
Results and Discussion
Figure 1. Experimental and simulated powder XRD patterns of com-
pounds 1–6.
Description of Methods for the Synthesis of Compounds 1–6
The structures of compounds 1 and 2 have been shown in
detail by Dong[20] and Wang,[18] respectively. However, in this
study, compounds 1 and 2 were synthesized successively by
one-pot synthesis though an environmentally friendly method.
That is different from that compound 1 was synthesized in a
MeOH solution at room temperature by Dong[20] and com-
pound 2 was synthesized in water under heating condition by
Wang.[18] The structure of compound 3 has been reported by
Yu,[21] which was synthesized at 80 °C and the pH value was
5.0. In this study, it was synthesized in water at room tempera-
ture, which is an more environmentally friendly method than
that in the reference.[21] Compound 4 has an isomorphic frame-
work with compound 1, and has been synthesized by Dong[20]
using the same method as for 1. In this study, compound 4 was
prepared in an ethanol aqueous solution. This method is more
safer than using methanol solvent in the reference.[2] Com-
pounds 5 and 6 were synthesized successively at 80 °C in
aqueous solution by one-pot method in the previous work by
our research group.[16] That is a simple efficient and eco-
friendly aqueous solution method.
Thermal Decomposition of Compounds 1–6
Thermal stability is an essential parameter for energetic
compounds, because a higher thermal stability of an energetic
coordination catalyst could add the steady of the solid propel-
lant.[24] The thermal decomposition behaviors of the com-
pounds above were investigated by TG-DSC. For compound 1
[Figure 2(1)], there is only one exothermic peak, which starts
at 233.3 °C and ends at 340.2 °C in the DSC curve with the
peak at a temperature of 291.5 °C, which represents the main
decomposition process of the framework. The heat release of
compound 1 is 1050.2 J·g–1. The corresponding TG curve of
compound 1 shows that 1 undergoes a continuous weight-loss
process from 197.5 to 539.2 °C, which is caused by the frame-
work structure decomposition, producing some small solid and
gas intermediate products with a lot of heat release in that
stage. As the temperature increases, these intermediates are
further decomposed and accompanied by a weak mass loss
process. Finally, compound 1 completely converts to CoO with
a residue weight percentage of 24.8%, which is closed to the
calculated value 24.0%.
PXRD Analysis
The exothermic peak of compound 2 [Figure 2(2)] starts at
PXRD patterns of compounds 1–6 were investigated in the 224.2 °C and ends at 330.9 °C with the peak at a temperature
solid state at room temperature (Figure 1). The experimental of 252.9 °C, and the heat release of the decomposition process
results are in good agreement with the simulated data based of compound 2 is 1146.4 J·g–1. There are two weight-loss
on the single-crystal structure analysis, indicating that the co- stages in the TG curve of 2, and the remaining weight corre-
ordination compound structures are solved accurately and the sponds to Bi2O3 with a residual amount of 37.9% (calcd.
products are single phase.
39.0%).
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Table 1. The decomposition temperatures and the heat release of com-
pounds 1–6.
ΔHb) /J·g–1
a)
Compound
Texo /°C
1
2
3
4
5
6
291.5
252.9
190.8
278.3
242.8
256.5
1050.2
1146.4
732.4
706.2
1004.8
982.6
a) Texo = decomposition peak temperatures of samples. b) ΔH = heat
release of the samples’ exothermic processes.
lytic activity. The thermal decomposition performance of
HMX can be improved by reduce the peak temperature and
increase the released heat through adding catalysts or addi-
tives.[5] In this study, the catalytic activity of all the prepared
samples were investigated by DSC measurement.
Figure 3 shows the DSC curves for pure HMX and HMX
with compounds 1–6, respectively. As shown in Figure 3(a),
there are two endothermic peaks and one exothermic peak in
the thermal decomposition of pure HMX. The first endother-
mic peak at approximately around 194.3 °C is attributed to the
phase transformation of HMX, and the second endothermic
peak at 278.2 °C is caused by the melting of HMX. The exo-
thermic peak for the HMX decomposition process is at
282.6 °C with the exothermic process value of 1047.6 J·g–1,
which agrees basically with the reported one.[23,25]
Figure 2. TG-DSC curves of compound 1–6.
TG data for compound 3 [Figure 2(3)] show the initial
weight loss step between 90.2 and 99.5 °C. The weight loss in
this temperature range is about 7.1%, corresponding to the loss
of all water molecules (calcd. 6.4%). The second obviously
weight loss above 167.2 °C corresponds to the decomposition
of the organic ligands. This weight loss process is identical to
the exothermic peak that appeared on the DSC curve at
190.8 °C with a heat release of 732.4 J·g–1. The remaining
weight corresponds to the CuO with residual amount of
29.0%. That is close to the calculated value of 28.5%.
For compound 4 [Figure 2(4)], there is only one exothermic
process from 244.0 to 293.2 °C, with the peak at a temperature
of 278.3 °C. This exothermic process represents the main de-
composition reaction of compound 4 and the heat release is
706.2 J·g–1. There is one weight-loss stage in the TG curve of
4, which is considered to be caused by the collapse of frame-
work structure. Finally, compound 4 completely converts to
MnO2, with a residue percentage of 26.2%, which is basically
consistent with the calculated value (28.1%).
The thermal decomposition process of compounds 5 [Fig-
ure 2(5)] and 6 [Figure 2(6)] have been described and analyzed
in detail in our previous paper.[21] The decomposition peak
temperatures (Texo) and the heat release (ΔH) of compounds
1–6 are given in Table 1. From the data in Table 1, one can
see that compounds 1–6 all have high decomposition tempera-
tures and high energy release, so one can conclude that all of
them are thermally stable energetic compounds.
Figure 3. DSC curves of HMX and mixtures of HMX and compounds
1–6, respectively.
Compared with the DSC curves of HMX in Figure 3, it is
worth noting that there is no significant impact on the phase
transition temperature of HMX with the addition of the com-
pounds. The endothermic peak of the HMX melting process is
Catalytic Effects of Compounds on the Thermal
Decomposition of HMX
The effects on the thermal decomposition of HMX are im- incorporated into the exothermic peak, and the onset tempera-
portant indexes for catalysts to evaluate their combustion cata- ture of the exothermic peak is lower than that of the pure
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HMX. The exothermic peak of HMX with compound 1 (curve also generate corresponding metal oxides at a molecular level.
b in Figure 3) starts at 239.5 °C and the decomposition peak Those metal oxides with different catalytic activity would not
temperature of HMX changes from 282.6 to 282.0 °C. The only change the decomposition mechanism of HMX but also
heat release of the exothermic process is 1333.1 J·g–1. The de- catalyze further thermolysis of NOx and the reactions among
composition peak temperature of HMX with the addition of 2 the products decompose from the HMX thermal decomposition
(curve c) changes to 279.6 °C, and the heat release of the exo- and accelerate the decomposition of the corresponding con-
thermic peak, which starts at 245.7 °C, is 1280.3 J·g–1. In curve densed-phase products, increasing the heat release.[5] In ad-
d, there appears a small exothermic peak at 192.4 °C before dition, considering the heat release of the compounds them-
the HMX exothermic peak, which is related to the framework selves in Table 1, it can be seen that there are no positive rela-
structure collapse of 3. This exothermic peak covers the HMX tionships between the catalytic activity and the heat release
crystal transformation peak. The decomposition temperature of of the energetic compounds themselves. For instance, the heat
HMX advances to 277.1 °C, and the total heat release increases release of compound 3 is not much, but it makes the mixture
up to 1127.5 J·g–1. With the addition of compound 4 (curve e), system heat up the most, and it was the best catalyst among
the exothermic peak starts at 253.4 °C, and the decomposition those energetic coordination compounds. Therefore, one can
temperature of HMX changes to 280.6 °C, with the heat re- conclude that the catalytic effect of the compounds on HMX
lease of 1145.4 J·g–1. The peak temperature of HMX contain- thermal decomposition could be closely related to the oxides,
ing compound 5 decreases to 281.0 °C and the heat release which come from the decomposition of the energetic com-
increases up to 1228.4 J·g–1, whereas these values for HMX pounds.
containing 6 reaches 279.0 °C and 1291.4 J·g–1. The peak tem-
peratures (Texo in °C) of the HMX decomposition process and
Synergetic Catalytic Effects of Coordination Compounds 1
and 2, 3 and 4, 5 and 6 on the Thermal Decomposition of
HMX
the heat release of the total heat release (ΔH in J·g–1) are listed
in Table 2.
Table 2. Catalytic effects of compounds 1–6 on the thermal decompo-
sition of HMX.
HMX mixtures, which consisted of HMX and the mixtures
of compounds, can produce multiple metal oxide in the decom-
position process and then could offer a wider range of selective
and synergetic catalytic effects. So the synergetic catalytic ef-
fects of the HMX mixtures on the thermal decomposition of
HMX were also researched. Figure 4 shows the DSC curves
Sample
Texo /°C
ΔH /J·g–1
Qa) /J·g–1
ΔTb) /°C
HMX
282.6
282.0
279.6
277.1
280.6
281.0
279.0
–1047.6
–1333.1
–1280.3
–1127.5
–1145.4
–1228.4
–1291.4
HMX+1
HMX+2
HMX+3
HMX+4
HMX+5
HMX+6
284.8
208.0
158.7
183.1
191.5
260.1
0.6
3.0
5.5
2.0
1.6
3.6
a) Q = measured value of the increased heat of the samples. b) ΔT =
advanced decomposition peak temperature of HMX with addition of
1–6.
Compared with the decomposition of pure HMX, the de-
composition peak temperature advanced 0.6, 3.0, 5.5, 2.0, 1.6,
and 3.6 °C and the heat release increased 284.8, 208.0, 158.7,
183.1, 191.5, and 260.1 J·g–1 through adding compounds 1–6,
respectively (Table 2). Herein, the values of the increased heat
are obtained by subtracting the heat of the compounds and
HMX itself. The decrease of the peak temperature and increase
of the released heat indicating that compounds 1–6 have obvi-
ously catalytic effects on HMX thermal decomposition.
According to the decreased values of the HMX decomposi-
tion peak temperature, their catalytic efficiency in descending
order is: 3 Ͼ 6 Ͼ 2 Ͼ 4 Ͼ 5 Ͼ 1. However, considering
the judgment criteria of the component compatibility of the
propellants, the more the temperature decreases, the poorer the
compatibility of the components is,[26] so we can not directly
judge the qualities of the catalysts from the decreased values
of the decomposition peak.
However, from the aspect of increasing the heat release, the
catalytic abilities are 1 Ͼ 6 Ͼ 2 Ͼ 5 Ͼ 4 Ͼ 3. This shows
that compounds 1–6 have different catalytic effects on HMX
thermal decomposition. During the thermal decomposition pro-
Figure 4. DSC curves of HMX with mixtures (1) M1–M5,
cess, the mixtures not only release much heat themselves, but (2) M6–M10, and (3) M11–M15.
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of HMX mixtures. Since the shape of the DSC curves are sim- the mixtures. The values of the SI are obtained to be 1.01,
ilar (the differences are the temperatures of exothermic peaks 1.15, 1.59, 1.30, and 1.21, respectively (Table 3). These results
and the heat release of the exothermic processes), the descrip- indicate that the co-existence of 1 and 2 show positive syner-
tions for DSC curves of HMX mixtures of compounds 1 and getic catalytic activity for the decomposition of HMX. When
2 were taken as examples. As shown in Figure 4(1), the DSC the mass ratio of 1 to 2 is 1:1, the system shows the best
curves of HMX with different mass ratio mixtures of com- synergetic effect on the thermal decomposition of HMX. We
pounds 1 and 2 have some differences with that of HMX with use the same formula to calculate the SI between compounds
1 or 2. Due to the addition of the mixtures of 1 and 2, the 3 and 4, 5 and 6 in different mass ratio, and the obtained values
decomposition peak temperatures of HMX change to 280.7, are listed in Table 3. When the mass ratio of 3 to 4 is 1:2, as
280.5, 280.0, 279.8, and 279.8 °C. The heat release of the exo- well as 5 to 6 is 1:2, the systems show the best synergetic
thermic processes are 1322.9, 1355.5, 1451.8, 1369.9, and effect on the thermal decomposition of HMX, respectively.
1293.6 J·g–1, respectively. Compared with pure HMX, the heat
As shown in Table 3 and Figure 4, three synergistic catalytic
release of HMX with the mixtures increased by 268.3, 299.0, systems all show good synergistic effects, and the mixtures at
391.3, 305.4, and 275.9 J·g–1, respectively. All the data, includ- different mass ratio have different synergetic catalytic effect
ing HMX with the mixtures of compounds 3 and 4, 5 and 6, on the HMX thermal decomposition, indicating that the SI in
are summarized in Table 3.
the same system are related to the proportion of the com-
pounds. The sequence of the biggest synergetic index in each
HMX mixture system is copper-manganese system (com-
pounds 3 and 4) Ͼ iron-bismuth system (compounds 5 and 6)
Ͼ cobalt-bismuth system (compounds 1 and 2). Therefore, the
synergistic catalytic effect is related to the compound composi-
tion of the system. In addition, the bismuth-cobalt system and
the bismuth-iron system all have bismuth based compounds,
and cobalt and iron both belong to iron-based elements. But
the SI of bismuth-iron system is higher than that of bismuth-
cobalt system, which may be due to the presence of iron in the
compound 6 in a multinuclear fashion.
Table 3. The synergetic effect of compounds 1 and 2, 3 and 4, 5 and
6 in different mass ratios on the thermal decomposition of HMX.
a)
Sample
Texo /°C ΔH /J·g–1
Q /J·g–1
Qa /J·g–1 SIb)
HMX
HMX+1
HMX+2
HMX+M1 280.7
HMX+M2 280.5
HMX+M3 280.0
HMX+M4 279.8
HMX+M5 279.8
HMX+3
HMX+4
HMX+M6 280.6
HMX+M7 280.4
HMX+M8 281.2
HMX+M9 281.3
HMX+M10 281.3
HMX+5
HMX+6
HMX+M11 280.6
HMX+M12 280.1
HMX+M13 280.1
HMX+M14 280.7
HMX+M15 280.9
282.6
282.0
279.6
–1047.6
–1333.1
–1280.3
–1322.9
–1355.5
–1451.8
–1369.9
–1293.6
–1127.5
–1145.4
–1090.8
–1206.0
–1146.6
–1114.8
–1065.6
–1228.4
–1291.4
–1353.6
–1406.9
–1339.9
–1282.1
–1277.3
284.8
208.0
268.3
299.0
391.3
305.4
275.9
158.7
183.1
263.9
378.6
318.2
285.3
235.6
191.5
260.1
318.1
371.8
305.8
248.9
244.6
265.6
259.3
246.4
233.4
227.2
1.01
1.15
1.59
1.30
1.21
277.1
280.6
164.8
166.8
170.9
175.1
177.0
1.6
2.23
1.86
1.63
1.33
Conclusions
Compounds 1–6 are all thermally stable energetic com-
pounds. They all have obviously different catalytic activity for
the thermal decomposition of HMX. The catalytic effects of
the compounds on HMX thermal decomposition are closely
related to the oxides, which come from the decomposition of
the compounds, but have no positive relationships with the
heat release of the compounds themselves. The mixtures of
compounds 1 and 2, 3 and 4, 5 and 6 can offer the synergistic
catalytic for HMX thermal decomposition. The synergetic in-
dex (SI) of the copper-manganese system is higher than those
of iron-bismuth and cobalt-bismuth system. The synergistic
catalytic effects are mainly related to the combination and pro-
portion of compounds in the systems.
281.0
279.0
208.7
214.1
225.8
237.5
242.9
1.52
1.73
1.35
1.05
1.01
a) Qa = arithmetic summation of the samples that compounds added
alone. b) SI = synergetic index of compounds 1 and 2, 3 and 4, 5 and
6 in different mass ratios.
Compared with the addition of a single compound, the ther-
mal decomposition peak temperature of HMX did not change
much after adding the mixtures. But the heat releases of HMX
mixtures are not a simple arithmetic summation of compounds
added alone. The interaction between compounds 1 and 2, 3
and 4, 5 and 6 initiate the synergetic effects, which are consid-
ered responsible for the increased heat release.
Experimental Section
Materials and Methods: All chemicals used for the synthesis were
obtained from commercial reagents of analytical grade and used with-
out further purification. The elemental analyses data (C, H, and N)
were carried out with a Vario ELIII elemental analyzer. Infrared (IR)
spectra were performed from KBr pellets with a FTIR-8400S spec-
trometer photometer in the 4000–400 cm–1 region. XRD experiments
for 1–6 were carried out with a Rigaku Mercury-CCD diffractometer
with graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å) at
We quantitatively evaluate the synergetic effect of the mix-
tures of compound 1 and 2 by using the synergetic index (SI)
[Equation (1)]:[27]
SI = Qm/(n1Q1 + n2Q2)
(1)
where Q1, Q2, and Qm are the increased heat release of HMX
with the addition of 1, 2, and the mixtures of them, respec-
tively, and the n1 and n2 are the mass fraction of 1 and 2 in 293 K. The structures were solved by direct methods and anisotropi-
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cally refined by least-squares on F2 procedures using the SHELXTL-
Samples Preparation for the Catalytic Effect of Compounds 1–6
97. Powder X-ray diffraction (PXRD) intensities were measured at on the Thermal Decomposition of HMX: To check the catalytic ef-
room temperature with a PANalytical XЈPert Pro diffractometer with fects of compounds 1–6 on the thermal decomposition of HMX, the
Cu-Kα radiation. DSC-TG for compounds 1–6 were carried out with a
compounds were mixed with HMX respectively at a mass ratio of 1:3,
Mettler Toledo DSC823E analyzer, and the samples were heated in a respectively, to prepare the test samples by grinding method.
temperature range of 50–600 °C with a heating rate of 10 °C·min–1 in
a flowing nitrogen atmosphere at 20 mL·min–1. The DSC tests for
HMX and HMX with additions were under the same condition with
DSC-TG but heated in temperature range 50–400 °C and all samples
were performed twice and the results were averaged.
Samples Preparation for the Synergetic Catalytic Effect on the
Thermal Decomposition of HMX: In order to study the synergetic
catalytic effect, mixtures of compound 1 and 2 at mass ratios of 3:1,
2:1, 1:1, 1:2 and 1:3 were prepared, which were named M1, M2, M3,
M4, M5, respectively. Mixtures of compounds 3 and 4 (M6, M7, M8,
M9, M10), 5 and 6 (M11, M12, M13, M14, M15) were also prepared in
the same way by grinding method to obtain them.
Syntheses of [Co(tza)2}n (1) and [Bi(tza)3]n (2): A mixture of
Co(NO3)2 (0.0582g, 0.2 mmol), Bi(NO3)3 (0.097g, 0.2 mmol),
NH2CH2COOH (0.0225g, 0.3 mmol), and Htza (0.1024g, 0.8 mmol)
were dissolved in ethanol (15 mL),. The mixture was transferred and
sealed in a 25 mL Teflon-lined stainless-steel reactor and heated at
130 °C for 72 h. After slowly cooling to room temperature, pink rect-
angle crystals (compound 1) were collected carefully from the wall of
container. Afterwards, the white powder at the bottom of the container
was filtered and washed with distilled water and ethanol several times,
respectively. The white powders were redissolved in Htza solution
(0.1 mol·L–1, 10 mL), stirred at 90 °C for 1 h and filtered. The filtrate
was placed at room temperature, and 10 d later, colorless block crystals
were (compound 2) obtained. Compound 1: Yield 41% (based on the
Htza). C6H6CoN8O4 (313): calcd. C 23.00; H 1.92; N 35.78%; found:
C 22.91; H 1.91; N 35.63%. IR (KBr): ν˜ = 3174 s, 3032 w, 2947 w,
1624 s, 1489 w, 1434 m, 1402 s, 1318 m, 1183 m, 1103 m, 1005 m,
932 m, 890 w, 809 w, 702 m, 663 m cm–1. Compound 2: Yield 39%
(based on the Htza). C9H9BiN12O6 (590.26): calcd. C 18.30; H 1.52;
N 28.46%; found: C 18.02; H 1.59; N 28.66%. IR (KBr): ν˜ = 3174
s, 3139 w, 3089 w, 3000 w, 2948 w, 2359 s, 2337 s, 1602 s,
1574 s, 1488 w, 1426 m, 1395 s, 1180 m, 1103 m, 854 w, 792 w,
709 m cm–1.
HMX mixtures consist of HMX and the mixtures of compounds 1 and
2, 3 and 4 or 5 and 6 at a mass ratio of 3:1 (HMX to the mixtures of
compounds). They were also obtained by grinding method.
Acknowledgements
This work was supported by the National Natural Science Foundation
of China (No. 21371159, 21201155 and 120247–13).
Keywords: Tetrazole-1-acetic acid; Synergetic catalytic
effect; HMX thermal decomposition
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Caution: Appropriate safety precautions should be taken.
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Received: March 19, 2017
Published Online: ᭿
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Z.-X. Wei,* Y.-Y. Qu, L. Kang, F. Xie, H.-D. Zhang,
P. Yue ................................................................................. 1–8
Synergistic Catalytic Effect of a Series of Energetic Coordina-
tion Compounds based on Tetrazole-1-acetic Acid on Thermal
Decomposition of HMX
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