Binary gas adsorption on molecular sieves. Experimental data for the adsorption of oxygen, nitrogen and oxygen-nitrogen mixtures on five molecular sieve adsorbents at various temperatures and pressures and a comparison with theoretical models.

Abstract

A study of adsorption equilibria of oxygen, nitrogen and oxygen-nitrogen mixtures on types 4A, 5A, 13X and Na-Mordenite molecular sieve pellets has been made. Pure component isotherms, using a volumetric apparatus, have been measured for each gas on each adsorbent at pressures up to 9 bar and for temperatures of 278.15,293.15 and 303.15 K. Curve fitting of the pure canponent isotherms has been attempted using the kinetic model of Gonzalez and Holland, the vacancy solution model, the statistical thermodynamic model and a mathematical equation similar to the Hill-de Boer model. With the exception of the kinetic model, good curve fitting was obtained. Binary equilibria data have been measured, using a constant volume method, for mixtures of oxygen and nitrogen at pressures of 1.7 and 4.4 bar and at temperatures of 278.15,293.15 and 303.15 K for each of the adsorbents. These results have been presented graphically as equilibrium phase compositions and corresponding total adsorption loadings. The binary experimental equilibria data have been examined against values predicted by mixture models (kinetic model, the extended vacancy solution model, the statistical thermodynamic model, the Cook and Basmadjian model, and the ideal adsorbed solution theory) using regression parameters obtained from the pure component isotherms. The statistical thermodynamic model and the ideal adsorbed solution theory gave the best representation of the experimental data. The activity coefficients of the adsorbed phase for the binary experimental data have been calculated and the results showed no appreciable deviation of the adsorbed phase from ideality.