PHASE-EQUILIBRIA IN SYSTEMS CONTAINING HYDROGEN, CARBON-DIOXIDE, WATER AND HYDROCARBONS

Vapor-liquid (VLE) and Vapor-liquid-liquid equilibrium (VLLE) data have been measured for the ternary mixtures water + n-hexadecane + carbon dioxide (CO2), benzene + n-hexadecane + CO2 and benzene + n-hexadecane + hydrogen and for the binary mixture CO2 + n-hexadecane at pressures between 10.1 to 30.1 MPa and at temperatures between 473.15 and 573.15 K. The applied experimental procedure is based on the static-analytical method. For equilibration, an autoclave (volume: 1000 cm3) with an electromechanically driven stirrer was used. Samples could be withdrawn from the autoclave through thermostated capillaries. For the analysis of the samples, the use of an on-line gaschromatograph was successful only for light components up to n-heptane. Therefore a conventional technique using cold traps to separate the samples into a liquid and a gaseous part including a subsequent analysis was applied. The experimental results could be correlated with simple equations of state (e.g. Peng-Robinson or Dohrn-Prausnitz) using van der Waals mixing rules with one interaction parameter k(ij) for each binary pair. For the determination of the k(ij) values, a robust optimization routine was developed. It works on the operating-system level of the computer (e.g. by using shell scripts on UNIX machines) and can handle program stops automatically.