Olefin/paraffin separations by adsorption: π-Complexation vs. kinetic separation



Monolayer dispersed AgNO3 on silica gel was prepared by thermal dispersion. This sorbent exhibited superior adsorption properties for olefin/parafin separations by selective adsorption of olefins through π-complexation. This sorbent, along with Ag+ ion-exchanged resin, was subjected to simulation studies for olefin/parafin separations by pressure-swing adsorption. Kinetic separations (due to differences in olefin/parafin diffusivities) using zeolite 4A and molecular-sieve carbon were also studied, Using 50/50 mixtures of C2 H4/C2 H6 and C3H6/C3H8, separations using these sorbents were compared directly based on olefin product purity, recoveiy, and throughput. The monolayer AgNO3/SiO2 sorbent showed superior separation results for C3H4/C3H8, and the Ag+-exchanged resin showed best results for C2H4/C2H6. In both cases, over 99% product purities could be obtained at reasonably high recoveries and throughputs. For C3H6/C3H6 separation on AgNO3/SiO2, multiplicity of cyclic steady states were observed within certain regions of feed and purge velocities. within these regions, two stable cyclic steady states were reached starting ffom different initial-bed conditions while all operating conditions were identical.