(414aa) Development of High Selectivity Mixed Matrix Oxygen Enrichment Membrane

Although low in cost, polymeric gas separation membranes often suffer from limitations in either permeability or selectivity in the polymeric materials. One successful approach has been to incorporate inorganic materials into the polymers to develop a durable mixed matrix membrane (MMM) with high selectivity and descent permeability. The success will depend on the proper selection of polymer, inorganic filler(s) and fabrication process. The relatively low cost of polydimethylsiloxane (PDMS), compatibility, nontoxicity, ease of fabrication and high permeability coefficients for wide range of gas species (with modest selectivity) make it suitable for mixed matrix membrane applications. 

We developed a PDMS membrane with different degrees of crosslinking and loading levels of nanoscale fumed silica to target the air separation applications at ambient conditions. The membranes are characterised using Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric and differential calorimetric analysis (TGA-DSC) and scanning electronic microscope (SEM). The synthesis procedure was optimized with the aim of developing durable and defect-free composite membranes with high O₂ selectivity and modest permeability. Preliminary results from gas permeation tests showed that the N₂ and O₂ permeabilities for neat PDMS membrane were about 719 and 1957 Barrer, respectively, with selectivity for O₂ over N₂ of 2.72. On the other hand, the silica-PDMS membrane not only exhibited much higher selectivity (7.4 for O₂), but also significantly lower permeabilities of 62 and 458 Barrer for N₂ and O₂, respectively. The improved performance of the composite membrane is attributed to the modified packing patterns and morphology of the membrane by the addition of silica nanoparticles in PDMS matrix. Some of thes results will be discussed in this paper.