A performance indicator for the screening of adsorbent/desorbent pairs for gas-phase simulated moving bed applications

In a simulated moving bed, the regeneration is accomplished by the introduction of a third species, the desorbent, which is later recovered by two downstream separations. As such, the choice of a proper adsorbent/desorbent pair is critical to ensure the effectiveness of the SMB process. While this can be done by comparing the separation region for each system, the computational effort required is extremely high. By developing a parameter that uses readily available literature data, the selection process is sped up and can be easily accomplished. In this work, an SMB performance indicator (SPI) is suggested. This indicator involves the trade-off between the adsorption selectivity in the presence of the desorbent, the adsorption capacity of the most retained species, and the ratio of the most and less retained species' enthalpies. The developed metric can select the most suitable adsorbent/pair for a specific gas separation by SMB through simple calculations.