Solubility measurement, correlation, and dissolution thermodynamics of 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane ? 1,3,5,7-tetranitro-1,3,5, 7-tetrazocane (2HNIW?HMX) co-crystal in two binary solvent mixtures

The solubility of 2HNIW center dot HMX co-crystal in two binary solvent mixtures (ethanol + methyl acetate, and 1,2-dichloroethane + methyl acetate) was measured by gravimetric method at various temperatures (283.15, 288.15, 293.15, 298.15, 303.15, 308.15, 313.15 and 318.15 K) under atmospheric pressure (0.1 MPa). The experimental results revealed that the solubility for co-crystal in binary solvent mixtures is a simple function of ethanol (or 1,2-dichloroethane) mass fraction and temperature, which decreased with increasing temperature and mass fraction of ethanol (or 1,2-dichloroethane) in the binary solvent mixtures. The solubility of 2HNIW center dot HMX co-crystal was correlated with the modified Apelblat equation, CNIBS/R-K model, Jouyban-Acree-van't Hoff model, and Jouyban-Acree-Apelblat model. The fitting results demonstrate that the modified Apelblat model and CNIBS/R-K model provided a better correlation with the experimental results than the other models. Furthermore, the van't Hoff equation was used to study the thermodynamic properties of the 2HNIW center dot HMX co-crystal dissolution process, including the apparent molar enthalpy change (DdisH degrees ), the apparent molar entropy change (DdisS degrees ), and the apparent molar Gibbs free energy change (DdisG degrees ). The results show that the dissolution of the co-crystal in the selected binary solvent mixture is an exothermic process. The experimental and calculated solubility data and thermo-dynamic properties of the 2HNIW center dot HMX co-crystal would be helpful for selecting the appropriate solvent system for the reaction, crystallization, and purification of the 2HNIW center dot HMX co-crystal.(c) 2022 Elsevier B.V. All rights reserved.