PHASE-BEHAVIOR OF CARBON-DIOXIDE PLUS 1,2-EPOXYCYCLOHEXANE MIXTURES

The two-phase boundaries of mixtures of carbon dioxide and 1,2-epoxycy clohexane (cyclohexene oxide) were determined at 343 K, 363 K, 383 K, and 405 K for cyclohexene oxide mole fractions of 0.02 < x(2) < 0.65. The bubble/dew points were determined visually in a windowed, variable volume, high-pressure cell during isothermal expansions and compressi ons of mixtures of known overall composition. Pressure-composition dia grams were constructed from the experimental data, and the critical po ints of the mixtures were determined for each temperature from these p hase diagrams. Although the Peng-Robinson equation of state slightly o verestimated the critical pressure, an excellent fit of the remainder of the bubble and dew point data was obtained with a binary interactio n parameter of 0.05. Anomalous phase behavior, in the form of remarkab ly high dew point data, was observed at 383 K and 405 K. H-1 NMR resul ts of the cyclohexene oxide from these experiments suggest that this w as due to the formation of poly(cyclohexene ether). The formation of t his polymer may have been catalyzed by trace amounts of water in the s ystem. This polymer has a low solubility in CO2; therefore, its presen ce increased the dew point pressure.