Thermodynamics of mixed‐gas adsorption

TLDR

The study proposes a simple method to compute adsorption equilibria of gas mixtures from pure‑component adsorption data at the same temperature and adsorbent. The method derives a Raoult‑law–like expression by treating the adsorbed phase as an ideal solution, linking each component’s partial pressure to its mole fraction and pure‑component adsorption pressure at identical temperature and spreading pressure. The predicted isotherms for methane–ethane, ethylene–CO₂, CO–O₂, and propane–propylene on activated carbon and silica gel match experimental data closely, demonstrating the approach’s accuracy and engineering utility.

Abstract

Abstract A simple technique is described for calculating the adsorption equilibria for components in a gaseous mixture, using only data for the pure‐component adsorption equilibria at the same temperature and on the same adsorbent. The proposed technique is based on the concept of an ideal adsorbed solution and, using classical surface thermodynamics, an expression analogous to Raoult's law is obtained. The essential idea of the calculation lies in the recognition that in an ideal solution the partial pressure of an adsorbed component is given by the product of its mole fraction in the adsorbed phase and the pressure which it would exert as a pure adsorbed component at the same temperature and spreading pressure as those of the mixture. Predicted isotherms give excellent agreement with experimental data for methane‐ethane and ethylene‐carbon dioxide on activated carbon and for carbon monoxide‐oxygen and propane‐propylene on silica gel. The simplicity of the calculation, which requires no data for the mixture, makes it especially useful for engineering applications.