Solubility and Phase Behavior of CL20 and RDX in Supercritical Carbon Dioxide

CL20, a high-energy explosive compound, is a polyazapolycyclic caged polynitramine (2,4,6,8,10,12- Hexanitro- 2,4,5,8,10,12-hexaazaisowurtzitane). The combustion and detonation characteristics of CL20 can be improved if it is formed into nanoparticles of uniform size. A new, promising process for particulation of materials utilizes environmentally benign compressed gases as either solvents or anti-solvents. Predictive models are required to describe the solubility and phase behavior of supercritical solutions of CL20 and supercritical carbon dioxide and for process simulation and development. Here, the solubility of CL20 in supercritical carbon dioxide was evaluated using the Peng-Robinson cubic equation of state. Critical properties, vapor pressure, and other required thermodynamic properties were estimated using a variety of available estimation techniques. A Fortran program to predict the solubility of CL20 was developed during the course of this project. The program was validated using available literature data for the solubility of naphthalene and of biphenyl in supercritical carbon dioxide. The applicability of the estimation techniques employed for the critical properties for CL20 was established using these same techniques to estimate the critical properties of comparable compounds, including RDX and HMX. Solubility data for RDX in supercritical carbon dioxide reported in the literature were also used to establish the validity of the estimation approach. Solubility was predicted over the temperature range of 305.15 to 368.15 K and over the pressure range of 74 to 150 atm. In general, as the temperature increases, the solubility decreases, while as the pressure increases, the solubility increases. See also ADM001736, Proceedings of the Army Science Conference (24th) held in Orlando, FL on 29 Nov-2 Dec 2004. Prepared in collaboration with Mississippi State University, Starkville, MS. Prepared in cooperation with Army Armament Research, Development and Engineering Center (ARDEC), Picatinny Arsenal, NJ.