Magnetically stabilized fluidized bed for gas separations: olefin-paraffin separations by π-complexation

The feasibility of using magnetically stabilized fluidized beds (MSB) for olefin-paraffin separations by pressure swing adsorption (PSA) is studied by model simulation, and the results are compared directly with that using packed beds. The sorbent used for the separations is an Ag+ exchanged resin that selectively forms π-complexation bonds with olefins, with the heat of adsorption of approx.10 kcal/mol. Superior separations are obtained with MSB for two reasons: high flow rates and small particle sizes that are allowed in MSBs resulting in high diffusion time constants (De/R2) (which are favorable for equilibrium separation). Lower temperature excursions compared to packed bed also favor the separation. The larger axial dispersion in the MSB has only minimal adverse effects on the PSA separation. For example: for a 14/86 ethane/ethylene feed mixture at the same feed throughput (120.8 L(STP)/[h (kg of sorbent)], an ethylene product at 99.9% purity is obtained at over 50% ethylene recovery from the MSBs whereas only 14% recovery at the same purity is obtained with the packed beds. Acceptable separation results are also achieved with MSBs for propane-propylene separation, but not with fixed beds.