Polymer based membranes for propylene/propane separation: CMS, MOF and polymer electrolyte membranes

Propylene/propane separations are generally performed by distillation which are energy intensive and costly to build and operate. There is therefore high interest to develop new separation technologies like membrane modules. In our previous paper, we collected, analyzed and reported data for neat polymers and mixed matrix membranes (MMM) based on flat and hollow fiber configurations for propylene/propane separations. In this second part, we collected the data for carbon molecular sieving (CMS) membranes from polymer pyrolysis reaction and metal-organic framework (MOF) membranes from different fabrication methods, as well as data on facilitated transport membrane-polymer electrolyte membranes (PEM). CMS membranes show great potential for C3H6/C3H8 separation with an optimum pyrolysis temperature around 500-600 celcius. However, physical aging is a concern as the micro-pores shrink over time leading to lower permeability. The performance of MOF membranes are above the 2020 upper bound of polymer-based membranes, but have limited commercial application because they are fragile and difficult to produce. Finally, facilitated transport membranes show excellent propylene/propane separation performance, but are less stable compared to commercial polymeric membranes limiting their long-term operation and practical applications. As usual, there is no universal membrane and the selection must be made based on the operating conditions.