High-pressure phase-equilibrium studies by gas-liquid partition chromatography



An elution gas that might be either a single component or a binary mixture, but which in any case was appreciably soluble in the fixed liquid phase on the column matrix material, was used to form a multicomponent liquid phase within the chromatographic column. Vapor-liquid equilibrium was studied both with the solute of interest at essentially infinite dilution conditions and with the solute present at some finite concentration in both phases. From the elution data vapor-liquid equilibrium ratios, or K values, were calculated by expressions relating the solute retention volume to the solute K value in the vapor-liquid system maintained within the chromatographic column.

Data were taken for the solutes ethane, propane, and n-butane at infinite dilution in the methane-n-decane system at 160°, 70°, 40°, 0°, and −20°F from 20 to 2,000 lb./sq. in.; for propane at infinite dilution in methane-n-hexadecane at 70°F and 20 to 200 lb./sq. in.; and propane in the system methane-propane-n-decane at 40°F from 20 to 460 lb./sq. in. The univariant gas-liquid-solid locus was experimentally determined for the methane-n-decane binary system.

The chromatographically determined K values for n-butane at infinite dilution in methane-n-decane were compared with published static equilibrium values and found to be in substantial agreement. Activity coefficients calculated from the data for all the solute isotherms were compared at atmospheric pressure with the results of the Brönsted and Koefoed relation for estimating activity coefficients of hydrocarbons, and close agreement was again found.