Challenges in characterizing adsorbents for gas storage and separation

Porous adsorbents, including activated carbons, zeolites, silicas, and newer materials such as metal-organic frameworks, have been investigated extensively for gas storage and separation applications. A key consideration is the performance of a material in terms of both its pure gas and multicomponent adsorption behavior, and so measuring accurate gas adsorption data is essential both to assess the suitability of an adsorbent for a given application and for process design and optimization. This article therefore provides an overview of the information required for gas storage and separation applications, the most common laboratory techniques used to obtain such data, with a focus on multicomponent equilibria measurements, and the main challenges associated with this process. We cover challenges for high pressure pure gas adsorption, multicomponent gas adsorption equilibria, kinetic gas adsorption and diffusion measurements, and the difficulty of accurately defining and calculating adsorption capacities. Recent developments, including porous reference materials for high pressure gas adsorption, and new techniques and apparatus for multicomponent gas adsorption equilibria measurements, are also highlighted.