Lewis, Gilliland, Chertow, and Hoffman [J. Am. Chem. Soc., 72, 1153-1 157 (1950)] measured adsorption equilibria for pure propane, pure propylene, and binary mixtures thereof, on activated carbon and silica gel. Adsorbate capacity was high on carbon, but selectivity was poor. Selectivity was high on silica gel, but capacity was low. For silica gel (751 m²/g), the following pure component data were obtained at 25°C:

The following mixture data were measured at 25°C, over a pressure range of 752-773 torr:

(a) Fit the pure component data to Freundlich and Langmuir isotherms. Which gives the best fit? Which component is most strongly adsorbed?

(b) Use the results of the Langmuir fits in part (a) to predict binary. mixture adsorption using the extended Langmuir equation, (15-32). Are the predictions adequate?

(c) Ignoring the pure-component data, fit the binary-mixture data to the extended Langmuir equation, (15-32). IS the fit better than that obtained in part (b)?

(d) Ignoring the pure-component data, fit the binary mixture data to the extended Langmuir-Freundlich equation, (15-33). Is the fit adequate? Is the fit better than that in part (c)?

(e) For the binary-mixture data, compute the relative selectivity,

for each condition. Does a vary widely or is the assumption of constant a reasonable?

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Propane Propylene P, torr q, mmol/g q, mmol/g P, torr 11.1 0.0564 34.2 0.3738 25.0 0.1252 71.4 0.7227 43.5 0.1980 91.6 0.7472 71.4 0.2986 194.3 1.129 100.0 0.3850 198.3 1.168 158.9 0.5441 271.5 1.401 227.5 0.7020 353.2 1.562 304.2 0.843 550.7 1.918 387.0 555.2 1.010 1.928 468.0 1.138 760.6 2.184 569.0 1.288 677.8 1.434 775.0 1.562