110th Anniversary: Comments on Heterogeneity of Practical Adsorbents

Abstract

Most micro–mesoporous adsorbents used in practical adsorptive fluid (gas and liquid) separation processes are energetically heterogeneous. The adsorbent heterogeneity plays a significant role in establishing the shapes of the equilibrium adsorption isotherms (pure component or mixture), the corresponding heats of adsorption, and the adsorbate mass-transfer rates, which in turn determine the overall separation performance by a process. The sources of the adsorbent heterogeneity are discussed, and the pros and cons of several analytical heterogeneous models describing pure and multicomponent adsorption isotherms, heats, and adsorbate mass-transfer coefficients are analyzed. Several critical effects of the adsorbent heterogeneity on the equilibrium isotherms are presented with examples to describe the complexity of the subject. The overall effect of adsorbent heterogeneity on an adsorptive process performance will, of course, depend on the specific adsorbate–adsorbent–process design combination. The results ...