New virial-type model for predicting single- and multicomponent isosteric heats of adsorption

The virial isotherm for single-and multicomponent gas adsorption equilibria was used to derive a new predictive model for the isosteric heat of adsorption. The virial coefficients were considered with two different orders of temperature dependencies. The coefficients with a first-order dependence of the temperature reciprocal showed that the single-component isosteric heat of adsorption is temperature independent. However, those with second-order dependence of the temperature reciprocal showed that the single-component isosteric heat of adsorption can vary significantly with temperature. The latter form also showed when lateral or vertical interactions dominated. Both types of coefficients showed a significant temperature dependence of the multicomponent isosteric heat of adsorption. Differences between single-and multicomponent isosteric heats of adsorption, compared at the same temperature and partial loading, also increased with decreasing adsorbed phase mole fraction, decreasing temperature, higher adsorption affinity, and increasing nonideality.