Uncovering the potential of MSC CT-350 for CO2/CH4 separation toward the optimization of a Pressure Swing Adsorption process for biogas upgrading

A laboratory-scale fixed-bed column is employed to study the dynamic behavior of the carbon molecular sieve MSC CT-350 for CO2/CH4 separation. Breakthrough adsorption tests in single-component systems are carried out at different pressures (1, 3, 5, 6.5 and 8 bar) and constant temperature (20 °C). Moreover, an additional test is conducted with a 40% CO2/60% CH4 binary mixture at 3 bar. Desorption tests are performed by varying the purge-to-feed ratio (P/F) at 50%, 30% and 20%, optionally using a vacuum pump. Experimental results show that MSC CT-350 has a good CO2 adsorption capacity for each pressure, considerably higher than CH4. In the binary test, very slight differences are experimentally found in the adsorption kinetics and equilibrium adsorption capacity with respect to single-compound tests, which results equal to 2.16 mol kg−1 for CO2 and 0.302 mol kg−1 for CH4 at 3 bar, compared with 2.29 mol kg−1 for CO2 and 0.262 mol kg−1 for CH4 for the single-compoound counterparts. The time required for a complete regeneration decreases with the increase in purge flowrate and with the simultaneous use of the vacuum pump. Finally, CO2 adsorption is a reversible process as the CO2 adsorption capacity of the adsorbent is not significantly reduced when utilized in subsequent adsorption-desorption cycles.