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2,4(5)-Dinitroimidazole (2,4(5)-DNI) is an important energetic material, and it is also an important precursor for the preparation of drugs and energetic materials. In this study, the solubility of 2,4(5)-DNI in eleven pure solvents (chlorobenzene, benzene, 1,2-dichloroethane, toluene, water, isopropyl alcohol, ethyl acetate, acetonitrile, methanol, 1,4-dioxane and acetone) were measured by using a dynamic test method from 278.15 K to 323.15 K under 101.1 kPa. Four solubility models were used to fit the experimental data, which were ideal model, modified Apelblat equation, polynomial empirical equation, and λh equation. Meanwhile, the relative average deviation and root-mean-square deviation between the experimental data and the fitted data were also calculated. Furthermore, the three thermodynamic parameters, i.e., dissolution enthalpy, dissolution entropy and Gibbs energy were obtained based on solubility data. Finally, the crude product of 2,4(5)-DNI was crystallized with acetone as solvent, and the purity of the crystalline product was greater than 99.5%.

The sensitivity and properties of energetic materials strongly depend on their crystal morphology. In this article, spherical 1,1-diamino-2,2-dinitroethylene (FOX-7) was produced via a combination of the cooling crystallization method and repeated grinding technique. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), optical microscopy, scanning electron microscopy (SEM) and laser particle size analysis were used to characterize the structure, infrared characteristics, morphology, and particle size of the product. The results show that the obtained product has a smoother spherical morphology with granularity gradation and shows similar diffraction peak positions to raw FOX-7. Differential scanning calorimetry (DSC), thermal gravimetry (TG), and accelerating rate calorimetry (ARC) were used to analyse the thermal behavior of spherical FOX-7 under nonisothermal and adiabatic conditions. The thermal performance test results show that spherical FOX-7 releases energy faster and releases more energy as compared to raw FOX-7. These findings showed that the cooling crystallization method combined with the repeated grinding technique is suitable for efficient preparation of spherical FOX-7, which could greatly improve the thermal stability of FOX-7.

The problem whether 1-hydroxylmethyl-3,5,7-trinitro-1,3,5,7-tetraazacyclooctane is the key active intermediate for the synthesis of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) from urotropine or 3,7-dinitro-1,3,5,7-tetraazabicyclo[3.3.1]nonane (DPT) remains to be illuminated for decades. In this paper, the hydrolysis and nitrolysis of the esterified intermediate 1-acetoxymethyl-3,5,7-trinitro-1,3,5,7-tetraazacyclooctane (PHX) were studied to solve the long-standing puzzle. The 1H NMR spectrum and 13C NMR spectrum of the 1-hydroxymethyl-3,5,7-trinitro-1,3,5,7-tetraazacyclooctane were detected by tracking the hydrolysis of PHX, which provide direct experimental evidences for its existence. Meanwhile, it was found that 1-nitroso-3,5,7-trinitro-1,3,5,7-tetraazacyclooctane (MNX) is a stable intermediate in the nitrolysis of PHX to generate HMX, and the presence of small amounts of water in the nitrolysis of PHX not only stimulate the redox reaction between nitric acid and formaldehyde but also promote the reaction by hydrolyzing PHX to corresponding N-hydroxymethyl derivative, which verify that 1-hydroxymethyl-3,5,7-trinitro-1,3,5,7-tetraazacyclooctane is the key active intermediate in the synthesis of HMX.

HMX is one of the best high-energy explosives in military applications. In this paper, the reaction calorimeter (RC1e) was used to monitor the reaction process of HMX synthesis by the nitrourea method. The research results show that the heat release rate is large on the reaction feeding stage, the feed rate should be controlled. The thermal parameters, such as adiabatic temperature rise(ΔTad,r) and maximum temperature of the synthesis reaction (MTSR), were calculated for assessing the thermal hazard of HMX synthesis. Although the urea nitrification stage is safer, the operating conditions of other reaction processes also need to be redesigned to improve the process safety level. These studies have potential applications in inherently safer operating measures and safer storage and transportation.

The nitrolysis of 3,7-dinitro-1,3,5,7-tetraazabicyclo[3.3.1]nonane (DPT) to prepare 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) in fuming HNO3 between −8 °C to −36 °C was tracked by 1H-NMR. It is found that DPT converted to 1-nitroso-3,5,7-trinitro-1,3,5,7-tetraazacyclooctane (MNX) immediately at the end of the feeding course; MNX was then gradually nitrolyzed to HMX. The latter reaction followed a pseudo-first order kinetics, and the selectivity of HMX was almost unaffected with the change in reaction temperature based on the kinetics study. The effects of water and N2O4 on this reaction were investigated and the results indicated that a small amount of water and N2O4 was beneficial to the generation of the intermediate product MNX. On the contrary, the presence of water and N2O4 hindered the conversion of MNX to HMX. Nitrosonium in the reaction system has two sources: one is from the nitrogen oxides such as N2O4 in fuming nitric acid; the other is from the redox reaction between nitric acid and formaldehyde, which was promoted by the H2O in fuming nitric acid. Based on the these results, the overall yield of the stepwise method for preparing HMX was up to 82.7% under the optimized reaction conditions.