(30f) Phase Behavior of the Tri-Tertiary-Butyl Benzene– Supercritical Carbon Dioxide System

Because of its remarkable solubility in high pressure carbon dioxide, tri-tert-butyl benzene is investigated as a novel candidate binder for metal casting operations, in which removal of the binder can be achieved with supercritical carbon dioxide. Removal of tri-tert-butyl benzene from a bound sand plug is demonstrated at 7 MPa and 25 oC in a high-pressure variable volume sapphire cell. To understand the dissolution mechanism and determine the optimum processing conditions, phase behavior of tri-tert-butyl benzene-supercritical carbon dioxide binary system is studied by measuring the dew and bubble points of the binary system at constant temperatures between 25-55 oC. In this temperature range, solubilities up to 70 wt % tri-tert-butyl benzene are attained at pressures ranging from 5-13 MPa. The system shows a lower critical solution temperature system behavior, requiring higher pressure to reach single phase with increasing temperature. During the phase behavior experiments, densities of the binary system at the phase boundary are determined. The phase behavior of the tri-tert-butylbenzene-carbon dioxide binary system is modeled with Peng-Robinson equation of state.