Physisorbents like zeolites, activated carbons, silica, and alumina gels have been traditionally used for separation of bulk or trace carbon dioxide from a gas mixture using a pressure or a thermal swing adsorption process. These processes are generally operated at near ambient or at moderate temperatures (say <100 °C) because the equilibrium sorption capacity and selectivity of sorption of CO2 on the physi-sorbents rapidly decrease at higher temperatures. Recently, a variety of reversible CO2 chemisorbents have been developed which offer decent sorption capacity and high selectivity for CO2 at relatively higher temperatures (∼150 to 500° C). Some of these chemisorbents even exhibit high selectivity of CO2 sorption in the presence of H2O which is mechanistically impossible for a physisorbent. Consequently, these chemisorbents can be used in (a) sorption enhanced reaction (SER) concepts for production of fuel-cell grade H2 from natural gas by low temperature steam-methane reformation reaction at ca. 400-500° C or from synthesis gas by water-gas shift reaction at ca. 200-400° C, and (b) removal and recovery of CO2 from a flue gas at a temperature of 150-200° C without precooling, predrying, and precompression. A comprehensive review of this subject is presented.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Industrial and Manufacturing Engineering