Zeolites: Their Features as Pressure Swing Adsorbents and CO₂Adsorption Capacity

Abstract

Industrial gas drying, dilute gas mixtures purification, air fractionation, hydrogen production from steam reformers and petroleum refinery off-gases, etc are conducted by using adsorptive separation technology. The pressure swing adsorption (PSA) has certain advantages over the other methods, such as absorption and membrane, that are a low energy requirement and cost-effectiveness. A key component of PSA systems is adsorbents that should be highly selective to a gas being separated from its mixture streams and have isotherms suitable for the operation principle. The six standard types of isotherms have been examined in this review, and among them the best behavior in the adsorption of CO2 as a function of pressure was proposed in aspects of maximizing a working capacity upon excursion between adsorption and desorption cycles. Zeolites and molecular sieves are historically typical adsorbents for such PSA applications in gas and related industries, and their physicochemical features, e.g., framework, channel structure, pore size, Si-to-Al ratio (SAR), and specific surface area, are strongly associated with the extent of CO2 adsorption at given conditions and those points have been extensively described with literature data. A great body of data of CO2 adsorption on the nanoporous zeolitic materials have been collected according to pressure ranges adsorbed, and these isotherms have been discussed to get an insight into a better CO2 adsorbent for PSA processes.

Studies on the CO2 adsorption onto coal fly ash zeolites at elevated pressures

“…The pressure-swing adsorption (PSA), at which the adsorption mode is performed at elevated pressures, while the regeneration mode is accomplished by depressurizing is widely investigated and developed. PSA is preferable process when highly porous materials such as zeolites are used as adsorbents, as the amount of adsorbed gas increases with increasing pressure due to the effects of capillary condensation into the pores (Kim et al, 2014). PSA is also considered as a technologically feasible process for production of fuels by separation of hydrogen from CO2/H2 syngas or when catalytic chemisorptions is performed for CO2 methanation (Moon et al 2016).…”