High gas permeability of nanoZIF-8/polymer-based mixed matrix membranes intended for biogas purification

The production of biomethane from the biogas purification process depends on the capacity of the separation technique employed to separate methane from carbon dioxide. Mixed matrix membranes (MMMs) combine the benefits of polymeric and inorganic materials, and it is believed that the trade-off between gas permeability and selectivity in polymeric membranes can be hampered by MMMs. Until recently, the development of MMMs for the biogas purification process has been constrained in lab scales. To be applied in large scales, the increase in gas permeability as well as the membrane performance under the influence of CO2 plasticization needs to be investigated. This paper reports the evaluation of gas permeability and CO2/CH4 gas separation performances of nano zeolitic imidazolate framework (ZIF)-8/Pebax-1657 to be used for biogas purification processes. In addition, the study on the CO2 plasticization behavior of MMMs fabricated with co-polymer Pebax was investigated. The incorporation of nanoZIF-8 particles inhibited the increase of CO2 permeability due to the reduced polymer flexibility. In addition, the diffusional selectivity of ZIF-8 improves the permeation behavior of both gases through MMMs. With nanoZIF-8/Pebax-1657 MMMs, the incorporation of particles improves the gas permeability with a slight decrease in gas selectivity, indicating a potentiality of the membranes used for biogas purification processes.