Development of mixed matrix membranes based on zeolite Nu-6(2) for gas separation

This work describes the preparation, characterization and application of hybrid organic/inorganic mixed matrix membranes made from inorganic phase Nu-6(2) as the molecular sieve and polysulfone Udel® as the organic phase. Due to the hydrophobic character of both the zeolitic phase (prepared with a high Si/Al ratio of 45, in contrast to the Si/Al = 1 of the commonly used zeolite A) and the polysulfone polymer, membranes obtained from these two phases are free of interfacial voids, as observed by SEM characterization and inferred from the membrane performance. Gas permeation tests carried out for the 50/50 H2/CH4 binary mixture revealed a significant enhancement of H2 separation. Under the same conditions of 538 kPa retentate pressure and room temperature, H2 permeability and H2/CH4 separation selectivity were 110 Barrer and 13 and 36 Barrer and 398, respectively, for the bare polysulfone membrane and for the Udel®-Nu-6(2) mixed matrix membrane. This superior performance of the hybrid membrane is attributed to the molecular sieve role played by the selected zeolitic phase which has two different types of eight-membered-ring channels with limiting dimensions of 2.4 and 3.2 Å.