A spherical FOX-7 crystal: Preparation, characterization, solubility and thermodynamic study

Abstract

ABSTRACT 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 (x DMSO = 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.