High Selectivity and Adsorption Capacity of Cation-Exchanged Zeolites for Biogas, Syngas, and Flue Gas Separation in a Pressure Swing Adsorption Unit

Abstract

Control over carbon dioxide emissions and recuperation is a priority that needs to be addressed urgently in the face of climate change. One of the most interesting techniques is pressure swing adsorption, which avoids having to heat and cool large amounts of matter and could be applied to industrially important carbon dioxide-containing gas mixtures, biogas, flue gas, and syngas. The technique relies on a stable, selective adsorbent. This work explores in depth the sodium- and calcium-exchanged zeolites of the FAU, MFI, and MOR topologies. It is shown that these zeolites have high adsorption selectivity for carbon dioxide at low pressures, high carbon dioxide recoveries, and high separation factors at overall good working capacities. The effect of the relative amounts of sodium and calcium on these properties enables tuning and picking of the material best suited for the desired application. The cation-exchanged faujasite zeolites demonstrated remarkable recovery of CO2 from biogas, syngas, and flue gas. For potential use as PSA adsorbents, the NaX and CaX zeolites stood out as two exceptional adsorbents due to their high CO2 uptake and recovery of CH4, H2, and N2.