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The crystal appearance of industrial grade 2,6-bis(picrylamino)-3,5-dinitropyridine (PYX) was mostly needle-shaped or rod-shaped with an average aspect ratio of 3.47 and roundness of 0.47. To improve the loading density and pressing safety, the crystal shape of PYX was optimized by cooling crystallization method. After recrystallization, the aspect ratio decreased from 3.47 to 1.28, and the roundness value increased from 0.47 to 0.78. XRD data showed that there is no crystal pattern change before and after recrystallization. The friction sensitivity of the explosive decreases from 88% to 56%, and the impact sensitivity decreases from 76% to 12%. Differential scanning calorimeter (DSC) was used to study the thermal decomposition of PYX. The thermal decomposition peak temperature of the samples after recrystallization was 4~7℃ higher than that of raw PYX. The adiabatic induction time (TMRad) and self-accelerating decomposition temperature (SADT) were calculated with AKTS software. In the same adiabatic induction time, the initial temperature of recrystallization PYX is about 30℃~40℃ higher than that of the raw PYX. The SADT is increased by about 50℃~60℃. The thermal safety of recrystallized PYX is improved. [ABSTRACT FROM AUTHOR]

The solubility of 1,1-diamino-2,2-dinitroethylene (FOX-7) in four binary mixed solvents (Dimethyl sulfoxide + Acetonitrile, Cyclohexanone, 1,2-Dichloroethane, 2-Propanol) was determined by using a laser dynamic method at temperatures from 293.15 to 333.15 K under 0.1 MPa. The measured results showed that the experimental solubility of FOX-7 increased with increasing temperature and Dimethyl sulfoxide content in the studied mixture solvents. Solubility data were well correlated by the modified Apelblat model, Yaws model and van't Hoff model, and the modified Apelblat model has the lowest root-mean-square deviation and can be used as the optimal model for data fitting. In addition, the thermodynamic parameters of the dissolution process, the surface tension, and surface entropy factor of FOX-7 were calculated based on the experimental data, which provided basic data for the optimization of crystallization process and industrial amplification of FOX-7. The cooling crystallization experiments were carried out in the investigated mixed solvents. The crystal morphology of FOX-7 obtained in the Dimethyl sulfoxide + Cyclohexanone mixed solvent (xDMSO = 0.3266) was regular, spherical, uniform in particle size, and have better thermal stability. Cyclohexanone could be the excellent non-solvent in the sphericalization of FOX-7. [ABSTRACT FROM AUTHOR]

As an intermediate in the synthesis of pesticide imidacloprid, imidazolidine is easily blended in imidacloprid products, which will lower the purity of the latter, thus affecting the using effects of it. The cooling crystallization method was used to study the distribution of imidazolidine. Taking the imidazolidine removal rate and partition coefficient as assessment criteria, the effect of the cooling rate, final crystallization temperature, crystallization time and addition of seed crystal on the migration of imidazolidine between liquid and solid phases was systematically studied, as well as the separation effect and product quality were evaluated. It was found that imidazolidine was most distributed in the solid phase at a higher cooling rate and a higher final crystallization temperature. The optimal process conditions for cooling crystallization were reached at the cooling rate of 0.2°C/min, the final crystallization temperature 15°C, the crystallization time of 5 h and the addition of seed crystal of 1%, under which the imidazolidine would remained in the liquid phase as much as possible. The final process yield was 83.62%, and the product purity was 99.70%. [ABSTRACT FROM AUTHOR]

The sphericity and size of ammonium perchlorate (AP) particles are the most significant properties in composite propellants. In this study, using the Taguchi method, the effects of surfactant type, surfactant concentration, stirring speed, cooling rate, and AP concentration parameters were investigated on the sphericity and size of AP particles in the cooling crystallization process (CCP). The sphericity and size of AP particles were calculated from the scanning electron microscopy (SEM) images by microstructure image processing (MIP) technique. The results showed that the selected parameters have sufficient effect on the sphericity and size of AP particles, based on analysis of variance. In this regards, the most effective parameters for sphericity and size optimization are the stirring speed and the surfactant type, respectively. Also, the AP concentration had the least effect on the sphericity and size of AP particles. Based on analysis of variance; the optimum sphericity and size equal to 0.84 and 21 μm, were predicted in CCP for AP particles, separately. Then, the particle sphericity of 0.84 and size of 23 μm was obtained from the suggested experimental optimal conditions. The differences between the predicted and experimental results are 1.7 and 8% for sphericity and size of AP particles, respectively. [ABSTRACT FROM AUTHOR]

The agglomeration of crystallized 1,4-diazahicyclo(2.2.2)octane was investigated in a turbulent agitated semibatch reactor. To modify the agglomeration of 1,4-diazabicyclo(2.2.2)octane, the crystallization operating factors, including the stirring rate, cooling rate, feed concentration, and aging, were studied. The mean particle size of the 1,4-diazabicyclo(2.2.2)octane in the product suspension increased with decreasing feed concentration and cooling rate. The products were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The product obtained at the condition of crystalline concentration of 1.80 glmL, stirring rate of200 rpm, and cooling rate of 0.3 K/min is hard to agglomerate. [ABSTRACT FROM AUTHOR]

The agglomeration of crystallized 1,4-diazabicyclo(2.2.2)octane was investigated in a turbulent agitated semibatch reactor. To modify the agglomeration of 1,4-diazabicyclo(2.2.2)octane, the crystallization operating factors, including the stirring rate, cooling rate, feed concentration, and aging, were studied. The mean particle size of the 1,4-diazabicyclo(2.2.2)octane in the product suspension increased with decreasing feed concentration and cooling rate. The products were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The product obtained at the condition of crystalline concentration of 1.80 g/mL, stirring rate of 200 rpm, and cooling rate of 0.3 K/min is hard to agglomerate. [ABSTRACT FROM PUBLISHER]