| dc.description.abstract | Propylene/propane separation by cryogenic distillation is energy-intensive and therefore non-thermal driven alternatives like membrane separations or adsorption processes can provide a significant cut in energy consumption. However, due to their similarities in sizes and molecular properties, separating propylene (4.0 Å) from propane (4.2 Å) still remains challenging. Traditional membrane materials, e.g. polymers, cannot provide commercially attractive selectivity and permeance at the same time and the need for novel membrane materials are imminent. Metal organic frameworks (MOFs), comprising of metal nodes and organic linkers connected by coordination bounds, have been regarded as one of the promising candidates, mainly because of their versatility for structural design.
Among MOFs, Zeolitic imidazolate frameworks, made primarily by Zn, Co, Cd metal nodes and imidazolate-derived linkers, showed reliable chemical, thermal and mechanical stabilities, offering ZIF-8 (Zn and 2-methylimiazolate), ZIF-67 (Co and 2- methylimidazolate), ZIF-90 (Zn and benzimidazolate) and several other materials that possess effective aperture sizes lying between the size of propylene and propylene. Further applications of ZIF membranes are mainly hindered by their expensive manufacturing costs. Some of the possible solutions are reducing the required membrane areas by 1) reducing the membrane thickness 2) slightly enlarging the effective aperture sizes 3) use better supports to provide high packing densities. This thesis tends to provide a comprehensive exploration of all these aspects to further the scaling-up of this green alternative route for paraffin olefin separations. | en |
