MODELING THE VAPOR-LIQUID-EQUILIBRIA OF 1,1,1-TRICHLOROETHANE + CARBON-DIOXIDE AND TOLUENE + CARBON-DIOXIDE AT 308-K, 323-K, AND 353-K

Vapor-liquid equilibrium data for binary mixtures of 1,1,1-trichloroethane + carbon dioxide and of toluene + carbon dioxide were collected at 308, 323, and 343 K, using a circulatory equilibrium cell. The data included saturated pressures ranging from atmospheric to near the mixture critical point (up to 12 MPa) and compositions of the two coexisting phases. The Peng-Robinson, cubic chain-of-rotators (CCOR), and Deiters equations of state were used to predict the saturated volumes and pressures of pure carbon dioxide and toluene. For the Peng-Robinson equation, binary interaction parameters were calculated for each set of data. The original model with one binary interaction parameter proved inadequate for correlation of the data. Use of a second interaction parameter resulted in better agreement between the model and data. The cubic chain-of-rotators equation of state represented the pure-component data well. For the binary vapor-liquid equilibria, this equation predicted the coexistence curve to be too narrow in the near-critical region and significantly underestimated liquid compositions at high pressures. The Dieters model yielded substantially poorer predictions of the saturated volumes of the vapor phase of the pure species. Given its complex form, extension to the binary mixtures was deemed inappropriate. The Peng-Robinson and cubic chain-of-rotators equations were used to correlate the binary data of this study, as well as existing data for the toluene + carbon dioxide system. The Peng-Robinson equation of state was shown to be superior for modeling two binary systems and, moreover, required less data to obtain the binary interaction parameters. © 1990, American Chemical Society. All rights reserved.