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

Abstract

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.