ESTIMATION OF ISOSTERIC HEATS OF ADSORPTION OF SINGLE GAS AND MULTICOMPONENT GAS-MIXTURES

Isosteric heats of adsorption of a single gas and the components of a multicomponent gas mixture as functions of adsorbate loadings are critical thermodynamic variables for design of practical adsorptive separation processes. The rigorous estimation of these variables is, however, not easy. A shortcut approximate method has been proposed by Bulow and Lorenz to circumvent this problem. A thermodynamic analysis of this method, however, shows that substantial errors can be introduced when the adsorbate loadings are high, the adsorbates are not very strongly adsorbed, and the adsorbent is energetically heterogeneous. A differential shortcut method is proposed which can be used to calculate the isosteric heats of adsorption as functions of adsorbate loadings provided that the total adsorbate loading (all components) isotherms for the pure gas and the binary gas mixture are known as functions of varying pressure at different constant values of the gas-phase mole fraction.