CO2/N2 separation by vacuum swing adsorption using a metal–organic framework, CALF-20: Multi-objective optimization and experimental validation

Abstract

• CALF-20 is a hydrophobic MOF commercialized for industrial CO 2 capture. • Experimental PVSA based CO 2 /N 2 separation on a MOF yielding 95% CO 2 purity. • Vacuum swing adsorption (VSA) experiments with 70 g of CALF-20. • Modelling & optimization of 2 VSA cycles to achieve US-DOE purity/recovery targets. • Experimental validation of VSA cycles to produce 95.5% CO2 purity and 88.1 %recovery. In this paper, the ability of CALF-20, a hydrophobic metal-organic framework (MOF), to capture CO 2 from dry flue gas (15/85 mol% of CO 2 /N 2 ) using two different adsorption configurations, basic four-step vacuum swing adsorption (VSA), and four-step with light-product pressurization (LPP) was evaluated. Pareto curves, for the simultaneous maximization of CO 2 purity and recovery, were generated. Five points from each Pareto curve representing five different process conditions were chosen to experimentally validate the model prediction. The experiments resulted in a CO 2 purity and recovery of 95%, and 70%, respectively for the basic four-step cycle, while the four-step LPP resulted in 95.5% purity and 88.1% recovery. The temperature history, the pressure transient, and the flow rate of different steps were in good agreement with the model predictions. The results of this study confirmed that CALF-20 is capable of separating CO 2 from dry flue gas, demonstrating the potential of the MOF for practical separations.