Critical temperatures and pressures for dilute supercritical fluid−entrainer systems are imperative for the design of efficient and environmentally conscious separation processes. In this study, the constant volume, visual method is used to measure the critical point of CO2 + acetone, CO2 + toluene, CO2 + propan-2-ol, CO2 + methylene chloride, CO2 + benzene, and ethane + benzene mixtures. The dilute entrainer concentration region is emphasized. The estimated experimental error for the critical temperature and pressure measurements is ±0.5 K and ±0.7 bar, respectively. Molar volumes are presented for all systems studied.

The effect of pressure on the measured bimolecular rate constant of the Diets-Alder reaction between maleic anhydride and isoprene was investigated in supercritical C 0 2 and subsritical propane. The reaction was carried out at 35°C in C 0 2 and 80°C in propane. Measured bimolecular rate constants are also compared to predictions from the thermodynamic pressure effect using transition state theory and the Peng-Robinson equation of state. The rate constants in supercritical C 0 2 agreed closely with the thermodynamic pressure effect predictions over the entire pressure range. Furthermore, the mole fraction based rate constants were found to vary linearly with the density of the solution. The rate constants in the sub-critical propane solvent significantly diverged from the thermodynamic pressure effect predictions and were round to deviate from this linear density dependence at the lower pressures studied. The results are interpreted in the context of local reactant concentrations about the reacting maleic anhydride and solvent-solute and cosolvent-solute interactions.

The properties designed into tires that make them strong and chemically resistant also inhibit their ability to be recycled easily Conventional liquid solvents do not sufficiently dissolve waste tires and tire production material for convenient separation. Supercritical water oxidation (SCWO) may provide an alternative solution to this environmental problem. Partial SCWO can be used as a means to partially break down rubber (polymeric) waste materials into lower molecular weight components that could be recovered as a chemical feedstock. In this study, the feasibility of converting waste material from tire production into useful products is explored. Batch SCWO studies illustrate the ability to efficiently break down the waste tire production material into a range of lower molecular weight organics for possible reuse depending on reaction conditions. Furthermore, a semi-continuous process has been developed and preliminary results are presented. Destruction efficiencies of greater than 0.9 were obtained in all runs regardless of reactor type. The results show SCWO to be a promising remediation alternative to the waste tire problem.