THE CONSTANT-PRESSURE HEAT-CAPACITY OF SUPERCRITICAL CARBON-DIOXIDE METHANOL AND CARBON-DIOXIDE ETHANOL COSOLVENT MIXTURES

The constant-pressure heat capacity ratio, C(PHP)/C(p atm) (where C(PHP) is the heat capacity at high pressure and C(p1 atm) the heat capacity at 1 atm) was measured for binary mixtures of carbon dioxide-methanol and carbon dioxide-ethanol. The data were obtained at pressures up to 82 bar for isotherms ranging from 320.0 to 333.2 K and are estimated to be accurate to +/-1.0% over most of the composition-temperature-pressure range. The methanol and ethanol co-solvent concentrations ranged from 0.77 to 1.88 mol%. No maximum in the heat capacity was encountered. The largest heat capacity ratio observed was 4.396 for a 1.27 mol% methanol in carbon dioxide mixture at 320.0 K and 82 bar. A model to correlate the heat capacity was developed.