Rapid screening of CO2-selective zeolites, carbons and MOFs by Five-step vacuum swing adsorption performances estimated with equilibrium theory analysis

It was aimed to evaluate a variety of conventional and emerging CO2-selective adsorbents, considering their use in a five-step VSA (Vacuum Swing Adsorption) system for flue gas capture. In most works, porous materials synthesised for CO2 capture were assessed by simply comparing their gas adsorption capacities measured at fixed pressures, without considering how they would perform in cyclic adsorption processes. Meanwhile it would be so laborious to conduct full numerical simulations of adsorption processes for evaluating and screening a number of adsorbents. In this study, zeolites, carbons and MOFs synthesised for CO2 capture were assessed and ranked with respect to the CO2 product recovery and the bed productivity of a five-step VSA, with an Equilibrium Theory model developed for the adsorption process. The simplified VSA model can provide the results so quickly, requiring only the adsorbent’s pure component adsorption isotherms in solving it. According to the simplified model, the CO2 recovery hinges upon the process operating conditions, i.e. adsorption-to-desorption pressure ratio and feed composition as well as equilibrium adsorption isotherms, i.e. the shape of CO2 isotherm and adsorbent’s selectivity of CO2 over N2. The bed productivity is influenced greatly by adsorbent’s CO2 adsorption capacity, also affected by the VSA’s CO2 recovery and adsorbent’s CO2 selectivity.