The study of gas‐solid equilibrium at high pressures by gas‐chromatography: Part I. Ethane, propane, and n‐butane at essentially infinite dilutions in the methane‐silica gel system

The measurement of vapor‐solid distribution coefficients or K values of a solute distributed between a gas phase and an adsorbed phase at essentially infinite dilutions has been investigated. Gas‐solid chromatography is the technique employed in which the solute of interest is eluted through a tube packed with a solid adsorbent by a flowing gas phase which may or may not be appreciably adsorbed. The data taken for the eluted solute samples were then related to the K value and isobaric heat of adsorption for the solutes in the vapor‐solid system. A previous mathematical solution describing the chromatographic process is extended to include the case of an appreciably adsorbed pure component elution gas. This theory allows the calculation of solute K values and heats of adsorption for a solute at essentially infinite dilution in the vapor‐solid system. It is necessary to have adsorption data for the elution gas covering the range of interest. For this reason the necessary elution gas adsorption isotherms were determined gravimetrically for the temperature and pressure range of the study. For comparison purposes a single ethylene adsorption isotherm at 25°C. was obtained along with retention volume data for methane, ethane, and propane at essentially infinite dilution in the ethylene‐silica gel system at 25°C. Agreement of the data of this study and the literature was thought to be sufficiently good to warrant further use of the technique. Methane adsorption isotherms on silica gel were gravimetrically measured at −40°, −20°, 0°, 20°, and 40°C. from 100 to 2,000 lb./sq.in.abs. Retention volume data over the same pressure and temperature ranges were taken for ethane, propane, and n ‐butane at essentially infinite dilution in the methane‐silica gel system.