MCM-41, MOF and UiO-67/MCM-41 adsorbents for pre-combustion CO₂ capture by PSA: Adsorption equilibria

Three different adsorbent materials, which are promising for pre-combustion CO₂ capture by a PSA (Pressure Swing Adsorption) process, are synthesized, pelletized and characterized. These materials are USO-2-Ni metal organic framework (MOF), mesoporous silica MCM-41 and a mixed material consisting of UiO-67 MOF bound with MCM-41. On these materials, equilibrium adsorption isotherms of CO₂ and H₂ are measured at different temperatures (25–140 °C) in a wide pressure range (up to 15 MPa). From the experimental data the parameters of different isotherm equations (Langmuir, Sips and Quadratic) are determined, together with the isosteric heats of adsorption. Binary adsorption of CO₂/H₂ mixtures on USO-2-Ni MOF is additionally measured and compared to predicted values using IAST (Ideal Adsorbed Solution Theory) showing a good agreement. The potential of the materials for the application of interest is evaluated by looking at their cyclic working capacity and compared to those of a commercial activated carbon. From this evaluation especially the USO-2-Ni MOF adsorbent looks promising compared to the commercial activated carbon. For the other two materials a smaller improvement, which is limited to lower temperatures, is expected.