Elevated temperature adsorbents for separation applications

Abstract

Elevated-temperature adsorptive separation involves the selective and rapid adsorption of gas molecules on weakly bonding chemical sites of an adsorbent at elevated temperatures (80–500 °C) and the reversible desorption of the gas molecules at a low cost. It is a significant step in several reactions, such as pre-combustion carbon capture, indirect/direct hydrogen production, ammonia separation, oxygen production from air, and carbon monoxide enrichment. This purification strategy avoids sensible heat loss of the feed gas, heat regeneration, accelerates adsorption kinetics, and can sometimes couple catalysts to achieve sorption-enhanced reactions. Before commercializing elevated-temperature adsorptive separation technologies, highly efficient syntheses for obtaining elevated-temperature-responsive adsorbents are required; competitive adsorption, interactions with gas impurities, and poisoning mechanisms need to be well understood; specific adsorption reactors and processes should also be designed. Therefore, this review covers the key progress made in terms of material design and synthesis, adsorption kinetic models and mechanisms, process design and optimization, as well as system integration for elevated-temperature adsorptive separation. This review will be valuable for the clean fossil-fuel utilization community, as well as energy and chemical industries.