FLUID PHASE EQUILIBRIA STUDIES FOR THE BINARY SYSTEMS CARBON DIOXIDE/N-BUTANE, DIMETHYL ETHER/N-BUTANE AND DIMETHYL ETHER/1-BUTENE (THERMODYNAMICS)

Vapor-liquid equilibrium measurements were performed on mixtures of carbon dioxide/n-butane, dimethyl ether/n-butane, and dimethyl ether/1-butene using a vapor-recirculation apparatus, working at isothermal conditions.; Experimental results for the system CO(,2)/n-butane are reported for nine isotherms in the temperature range from 4.75 to 145.33(DEGREES)C, and at pressures up to 8.17 MPa. Two isotherms lie below the critical temperature of CO(,2), where both components are subcritical, and seven were measured between CO(,2) and n-butane critical temperatures up to the mixture critical line. Internal consistency tests were performed by cross-plotting the data on P-x-y, P-T, T-x-y, and k value-P diagrams. The ability to represent the data using a two-parameter equation of state (SRK and P-R) was tested on selected isotherms, showing the SRK equation a marginally better fit than the P-R equation. The experimental results exhibited agreement with those of similar studies.; The phase diagram for the system DME/n-butane was obtained for eleven isotherms in the temperature range from 9.81 to 141.35(DEGREES)C, and pressures up to 4.85 MPa. Eight isotherms lie below the critical temperature of DME, where both components are subcritical. Three were measured between the DME and n-butane critical temperature up to the mixture critical line. No data have been previously reported for this system. The experimental results were evaluated by internal consistency tests and thermodynamic consistency tests based on the Maximum Likelihood Principle performed on the P, T, x, y data in the subcritical range of temperatures, where the excess Gibbs energy for the mixture was determined as a function of composition. A good representation for selected isotherms fitted using the SRK and the P-R equations of state was obtained.; A new vapor-recirculation apparatus for VLE measurements was built. It was designed to work at isothermal conditions in the temperature range from 0 to 250(DEGREES)C and pressures up to 40 MPa. The apparatus has heating and cooling units put in place by the use of an elevator. A "visual" equilibrium cell provides visibility of the mixture over the entire range of operation. The phase compositions are analyzed using a capillary column gas chromatograph with a Thermal Conductivity detector.; The system DME/1-butene was the first one to be studied in the new apparatus. One isotherm was studied at 69.8(DEGREES)C showing a narrow vapor-liquid coexistence region. No data for this system has been previously reported.