Gas Separation Properties of Mixed Matrix Membranes based on Polyimide and Graphite Oxide

In this work, three different graphene-based materials, namely graphite oxide (GrO), thermally reduced graphite oxide (T-RGrO) and ascorbic acid multi-phase reduced graphene oxide (AMP-RGO), were synthesized and used to produce mixed matrix membranes (MMM) based on Matrimid®5218 for as separation. From the samples produced, a complete set of characterization was performed including XRD, FTIR, TGA and SEM to relate with the gas separation performance using H2, CO2, O2, N2 and CH4. For all the gases studied, the results showed that membrane permeability was inversely proportional to the gas molecular size. This behavior was associated to multi-phase reduced graphite oxide (AMPRGO) being an excellent gas barrier for large gas molecules, especially for CH4. The results showed that the H2/CH4 ideal selectivity increased to 231 which represents a 328% improvement for M/AMP-RGO 0.1 compared to the neat matrix. The CO2/CH4 selectivity was 79.8 for M/AMP-RGO 0.2 wt.% which represents a 344% improvement compared to the neat polymer. These results confirmed that these membranes can be used for methane separation such as in ammonia plants (H2/CH4) or biogas upgrading/natural gas purification (CO2/CH4).