(227h) Olefin/Paraffin Separations Enabled by New High Capacity/Flux CMS Materials

Olefin/paraffin separations by fractional distillation are very energy intensive due to the small differences in boiling points; e.g., 5 °C for C₃H₈ vs. C₃H₆. Pressure swing adsorption (PSA) and membrane systems have the potential to significantly reduce the energy consumption. The heart of future successful PSA or membrane systems will be advanced materials. The development of novel Carbon Molecular Sieve (CMS) materials for olefin/paraffin separations derived from two families: (1) cation exchange resins and (2) polyvinylidene chloride copolymers will be discussed. Both the C2 and C3 olefin/paraffin separations can be addressed using these types of carbon molecular sieves because their micropore sizes can be fine-tuned by precursor copolymerization and thermal treatment. The micropore volumes in these new CMS materials are 30-75% higher than ones produced with Matrimid® polyimide resins, which translates into higher capacity for sorbent and flux for membrane applications.

There is significant barrier to scale up (> 10, 000 m²) thin film CMS membranes. PSA using CMS adsorbent pellets can potentially be commercialized sooner than membrane technology to provide an interim solution. However, PSA has much more complex set of transport processes and is an inherently dynamic process. The engineering of the PSA process using benchtop PSA experiments coupled with modelling (Aspen based) will also be discussed. PSA processes with additional steps from the basic Skarstrom cycle, i.e. co-current blowdown and effluent rinse, were investigated. Propylene purity of 89% at 89% propylene recovery was demonstrated using a 25% propylene-75% propane feed.