Solubilities of Octahydro-1, 3, 5, 7-tetranitro-1, 3, 5, 7-tetrazocine in Î³

Article pubs.acs.org/jced

Solubilities of Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine in γ‑Butyrolactone + Water, Dimethylsulfoxide + Water, and N‑Methyl pyrrolidone + Water Kwang-Joo Kim,*,† Hyoun-Soo Kim,‡ and Jeong-Seop Sim‡ †

Crystallization Process & Engineering Laboratory, Department of Chemical Engineering, Hanbat National University, San 16-1, Dukmyung-dong, Yusung, Daejeon 305-719, South Korea ‡ Agency for Defense Development, Yusung, Deajeon, South Korea ABSTRACT: Solubilities of octahydro-1,3,5,7-tetranitro1,3,5,7-tetrazocine in γ-butyrolactone + water, dimethyl sulfoxide + water, and N-methyl pyrrolidone + water were measured in the temperature range from 273.15 K to 363.15 K and mass fraction of water from 0 to 1.0. Activity coefficient and heat of dissolution were obtained from the solubility data.

1. INTRODUCTION HMX, or octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine shown in Figure 1 has four different crystal polymorphs. Of these, the

mixture of nonsolvent and solvent has not been presented. It is required for selection of solvent and determination of supersaturation in crystallization. In this study, mixed solvents including water as a nonsolvent were investigated. The aim of this work is to measure the solubility of HMX in various binary solvents as a function of temperature.

2. EXPERIMENTAL SECTION Materials. HMX (mole fraction purity of 99.9 %) was supplied from Hanwha Co. HMX was used without further purification. γ-Butyrolactone (BL, purity 99.9 %), N-methyl pyrrolidone (NMP, purity 99.9 %), and dimethyl sulfoxide (DMSO, purity 99 %) were of analytical purity grade (purchased from Aldrich), and redistilled deionized water was used. Measurement of Solubility. The solubilities of HMX in dimethyl sulfoxide + water, γ-butyrolactone + water, and Nmethyl pyrrolidone + water were measured by the isothermal method. The equipment used to measure solubility was presented in the previous study.8 It was equipped with a FBRM (Focused Beam Reflectance Method) probe, which can accurately and precisely online monitor and control the temperature. Apparatus was equipped with a 150 mL jacketed curved-bottom glass vessel, a downward glass propeller stirrer driven by motor, a temperature sensor, and a thermostatic bath controlled by a PID controller with ± 0.1 K accuracy. The temperature and number of particles were measured at 2 s intervals during the measurement of solubility.

Figure 1. Chemical structure of HMX.

β-form is the desirable one, since it has the highest density and the lowest sensitivity. The morphology of crystal depends mainly upon the crystallization conditions. Furthermore, the defect inside the crystal is largely determined by the solvent used in crystallization. The sensitivity of explosives depends mainly on the roughness of its surfaces and defects inside the crystals,1 which are determined in the crystallization condition. To minimize the sensitivity induced due to an unintentional shock, characteristics of explosives should be controlled. Recrystallization of HMX in various solvents was experimentally studied to reduce sensitivity of the HMX crystal.2,3 Crystallization using solvents is applied to change the characteristics of HMX.3−6 Cooling, evaporating, and drowning-out methods are available for the crystallization of HMX. To select an appropriate crystallization method, the solubility of HMX in solvents should be known. In the drowning-out method, the addition of a nonsolvent in the HMX solution generates a supersaturation by lowering its solubility. The ratio of nonsolvent to solvent is a key variable that determines supersaturation level.7 However, the solubility of HMX in a © 2013 American Chemical Society

Received: January 27, 2013 Accepted: July 31, 2013 Published: August 15, 2013 2410

dx.doi.org/10.1021/je400199m | J. Chem. Eng. Data 2013, 58, 2410−2413

Journal of Chemical & Engineering Data

Article

Table 1. Mole Fraction Solubilities of HMX (or Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) and Activity Coefficient in Binary Solvent at Temperature T, Solvent Composition w and Pressure 0.1 MPaa dimethylsulfoxide/water 100 wt % DMSO

80 wt % DMSO−20 wt % water

T/K

x·10

γ·106

x·103

γ·105

273.0 293.0 303.0 318.0 333.0 348.0

1.3151 1.3940 1.4906 1.5191 1.6437

8.7340 21.316 74.148 240.410 662.350

2.8071 5.2857 6.5048 11.568 16.518 24.920

4.9618 13.181 45.680 95.546 221.10 436.87

T/K

x·102

γ·106

x·103

303.0 273.0 288.0 318.0 333.0 348.0

3.8836 2.1893 3.0602 4.5079 5.4787 7.0217

76.512 6.3621 22.766 245.18 666.62 1550.5

6.0530 3.0127 4.3826 8.8896 12.937 19.440

100 wt % BL

x·104

γ·105


γ·104

2.8900 4.8196 3.6122 19.287 10.378 28.632 16.234 68.080 53.240 68.599 88.641 122.82 γ-butyrolactone/water

80 wt % BL−20 wt % water

100 wt % NMP

a


60 wt % BL−40 wt % water x·104

49.090 6.3577 46.737 4.6233 2.8909 4.8181 15.897 4.0467 17.216 124.33 10.515 105.11 282.31 20.892 174.81 560.03 35.729 304.71 N-methylpyrrolidone/water

80 wt % NMP−20 wt % water

x·106

γ·102

x·106

γ·102

8.7809 15.806 26.342 35.123 61.463 122.92

1.5862 4.4079 11.280 31.468 59.421 88.569

1.4367 3.5917 6.4651 10.775 17.958 38.071

9.6947 19.397 45.961 102.57 203.37 285.96


γ·104




x·105

γ·103

x·105

γ·102

11.556 7.2007 8.0007 16.000 19.555 26.664

25.713 1.9343 8.7079 69.076 186.76 408.29

2.1659 1.0830 1.4439 3.6098 5.0536 6.4974

13.719 1.2861 4.8249 30.618 72.268 167.56



T/°C

x·102

γ·106

x·103

γ·105

x·104

γ·104

x·104

γ·104

x·104

γ·104

273.0 288.0 303.0 318.0 333.0 348.0

2.1037 3.8863 5.5931 7.5733 9.4447 12.403

6.6210 17.927 53.126 145.94 386.69 877.79

4.1665 7.2275 16.298 26.158 39.311 57.644

3.3429 9.6395 18.231 42.252 92.906 188.86

7.2470 15.596 41.112 78.594 199.02 353.04

1.9220 4.4672 7.2276 14.063 18.351 30.837

3.1788 5.4362 9.1963 15.040 19.209 28.370

4.3816 12.816 32.311 73.488 190.13 383.74

1.6733 2.5098 3.8478 6.3556 9.1963 12.536

8.3239 27.751 77.224 173.90 397.14 868.43

The relative standard uncertainty in the solubilities ur(x) is 0.10. Standard uncertainties are u(T) = 0.1 K in temperature, u(w) = 0.1 wt %.

in the investigated temperature range, it leads to the following equation10

Predetermined amounts of solute and solvent mixture, about 100.0 g, were fed into the jacketed vessel. The amount of solvent was in small excess. After stirring at a fixed temperature for 1 h, an additional solute of known mass about (0.003 to 0.006) g was fed into the vessel with continuous stirring. This procedure was repeated until the last addition of solute could not dissolve completely within the interval of addition of 30 min. Then, the total amount of the solute added (including the last addition) was used to compute the solubility. To prevent the evaporation of the solvent, a condenser was used. The masses of the samples and solvents were weighed using an analytical balance (Metler Toledo) with an uncertainty of 0.00001 g. The dissolution of the solute was monitored by FBRM (Lasentec S400A). When the solute was dissolved completely, the solution was clear, and the particle was not detected. Some of the experiments were conducted in triplicate to check the reproducibility. The solubility for given mixture was reproducible within ± 0.01 g HMX/100 g solution.

ln x1Lγ1L = −

ΔfusH1 ⎛ T ⎞ ⎜⎜1 − ⎟⎟ RT ⎝ Tfus,1 ⎠

(1)

L

where x1 is the mole fraction of component 1 (HMX) in the liquid phase, γ1L is the activity coefficient of HMX in the liquid phase, ΔfusH1 is the molar enthalpy of fusion of HMX, Tfus,1 is the melting temperature of HMX, T is the absolute temperature of the mixture, and R the gas constant. The melting temperature Tfus,1 and the enthalpy of fusion ΔfusH1 of HMX are 558.15 K and 70154.38 J/mol, respectively.1 The activity coefficients γ1L were calculated by combining eq 1 with experimentally determined solution composition x and temperature T. Table 1 lists mole fractions, equilibrium temperatures, and activity coefficients according to the mass ratio of solvent to water. As can be seen in Table 1, deviations from ideal solution are observed for all the cases. The solubilities of the HMX have a deviation from ideal values in the order: DMSO > NMP > BL. Such deviations are attributed to the interaction of a chemical nature between the HMX and solvent. Figure 2 shows the solubility of HMX in various mixed solvents. The solubilities of HMX increase with increasing temperature and decrease with increasing the water content in solvent mixture. The overall average absolute errors11 of for DMSO−water, BL−water, and NMP−water are 2.3 %, 1.4 %,

3. RESULTS AND DISCUSSION The solubilities of HMX in solvents were measured over the temperature ranging from 273 K to 353 K. The activity coefficient was calculated from data of solubility against temperature . The fundamental equation used to calculate the solid−liquid phase equilibria can be derived from the isofugacity criterion.9 If solid−solid transition does not occur 2411



Article

0.000644, and 0.00137 for DMSO, BL, and NMP, respectively. Its temperature dependence is very low. Thus, cooling crystallization is not desirable in the pure solvent DMSO, BL, and NMP. Evaporation and drowning-out crystallizations are recommended. Solubility decreases very sharply according to the addition of water. This means that the drowning-out mode is acceptable in binary solvent including water. As temperature dependence on solubility in mixed solvents with water is high, the cooling mode is also applicable in the mixed solvents with water. To calculate the enthalpy of dissolution of HMX crystals in solvent, eq 1 can be changed into following ideal equation;9 ln x1 =

−Δsol H1 ⎛ 1 1 ⎞ ⎜⎜ − ⎟⎟ R ⎝T Tfus,1 ⎠

(2)

ΔsolH1 is equal to ΔfusH1 for an ideal system, which is obtained by taking γ1 = 1 in eq 1, and ΔfusH1 + ΔmixH1 for nonideal systems. The enthalpy of mixing, ΔmixH1, expresses a measure for the solute−solvent interaction, whereas the enthalpy of fusion ΔfusH1 is independent of solvent. The slope from the plot of ln x1 versus T−1, d ln x1/dT−1 equals to ΔsolH1/R. In results, ΔsolH1 was calculated from its slope multiplied with R, The values are listed in Table 2. ΔsolH1 of HMX in all solvents investigated was exothermic. Table 2. Heat of Dissolution and Heat of Mixing solvent composition

d(ln x)/d(T−1)

DMSO (wt %)/water (wt %) 100:0 384.981 80:20 2698.79 60:40 4552.78 40:60 3162.9 20:80 3937.4 BL (wt %)/water (wt %) 100:0 1402.215 80:20 2334.778 60:40 3226.888 40:60 1720.043 20:80 2392.765 NMP (wt %)/water (wt %) 100:0 2164.87 80:20 4775.48 60:40 5351 40:60 2287.64 20:80 2434.49

ΔsolH (kJ·mol−1)

ΔmixH (kJ·mol−1)

3.20073 22.4377 37.8518 26.2963 32.7356

−66.9593 −47.7223 −32.3082 −43.8637 −37.4244

11.658 19.4113 26.8283 14.3004 19.8934

−58.502 −50.7487 −43.3317 −55.8596 −50.2666

17.9987 39.7033 44.4882 19.0194 20.2403

−52.1613 −30.4567 −25.6718 −51.1406 −49.9197

In the cases of solvent without water, it was found that ΔmixH1 increases in the order: NMP > BL > DMSO. The larger ΔmixH1 results in the larger solvent−solute interaction, which leads to the larger effect on the inclusion of solvent inside the crystals. It supports the previous results that the crystals crystallized in solvent DMSO has a lower defect than those crystallized in pure solvent BL.3 Also, ΔmixH1 depends on the water content in the solvent. This supports that defect of HMX crystals prepared in pure solvent DMSO + water was lower, compared to that in pure solvent DMSO.3 The heat of dissolution of HMX in all solvents is very exothermic and indicates an energetically favorable mixing between HMX and solvent. The heat of dissolution for cyclotrimethylenetrinitramine in a binary mixed solvent suggested similar results.11

Figure 2. The mole fraction solubility, x, of HMX in the solvents. DMSO/water: ●, 100 wt %/0 wt %; ○, 80 wt %/20 wt %; ▼, 60 wt %/40 wt %; Δ, 40 wt %/60 wt %; ■, 20 wt %/ 80 wt %. BL/water: ●, 100 wt %/0 wt %; ○, 80 wt %/20 wt %; ▼, 60 wt %/40 wt %; Δ, 40 wt %/60 wt %; ■, 20 wt %/80 wt %. NMP:water: ●, 100 wt %/0 wt %; ○, 80 wt %/20 wt %; ▼, 60 wt %/40 wt %; Δ, 40 wt %/60 wt %; ■, 20 wt %/80 wt %.

and 1.2 %, respectively. The solubility of HMX in pure solvents, DMSO, BL, and NMP is very high. Temperature dependence on the solubility for pure solvents, Δx/ΔT is 0.000597, 2412



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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Teipel, U. Energetic Materials; Wiley-VCH: Weinheim, Germany, 2005; Chapter 3. (2) van der Heijden, A. E. D. M.; Bouma, R. H. Crystallization and Characteristics of RDX, HMX, and CL-20. Cryst. Growth Des. 2004, 4, 999−1007. (3) Youn, S. K; Kim, K. J. Effect of Solvent on HMX Crystallization; Sha, Z., et al., Eds.; BIWIC: Tianjin, China, 2012; pp 559−566. (4) Kroeber, H.; Teipel, U. Crystallization of Insensitive HMX. Propellants, Explos., Pyrotech. 2008, 1, 33−40. (5) Svensson, L.; Nyqvist, J.; Westling, L. Crystallization of HMX from γ-Butyrolactone. J. Hazard. Mater. 1986, 13, 103−108. (6) Teipel, U.; Förter-Barth, U.; Krause, H. H. Crystallization of HMX-Particles by Using the Gas Anti-Solvent-Process. Propellants, Explos., Pyrotech. 1999, 24, 195−198. (7) Kim, D. Y; Kim, K. J. Correlation between Quantity of Defect and Supersaturation in RDX Crystallization Using γ-Butyrolactone and Water as Solvent. Chem. Eng. Res. Des. 2010, 88, 1461−1466. (8) Jim, M.; Kim, K. J. Solubility of Forms I and II of Clopidogrel Hydrogen Sulfate in Formic Acid, N-Methylpyrrolidone, and N,NDimethylformamide. J. Chem. Eng. Data 2012, 57, 598−602. (9) Prausnitz, J. M.; Lichtenthaler, R. N.; Azevedo, E. G. Molecular Thermodynamics of Fluid-Phase Equilibria; Prentice-Hall, Inc.: Englewood Cliffs, NJ, 1986; Chapter 9. (10) Gmehling, J.; Anderson, T. F.; Prausnitz, J. M. Solid−Liquid Equilibria Using UNIFAC. Ind. Eng. Chem. Fundam. 1978, 17, 269− 273. (11) Kim, D. Y; Kim, K. J. Solubility of Cyclotrimethylenetrinitramine (RDX) in Binary Solvent Mixtures. J. Chem. Eng. Data 2007, 52, 1946−1949.

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Solubilities of Octahydro-1, 3, 5, 7-tetranitro-1, 3, 5, 7-tetrazocine in Î³

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