New adsorbents containing cuprous chloride dispersed on pillared interlayered clays (PILC) have been prepared and studied for olefin-paraffin separations. High surface-area PILC's were synthesized with different metal oxide (Al2O3, Fe2O3, TiO2 and ZrO2) as the intercalating pillars. Cuprous chloride was dispersed in a submonolayer form on these PILC's. Pure-component isotherms were measured for C2H4, C2H6, C3H6 and C3H8 at 25 degrees C and 60 degrees C. All sorbents exhibited high C2H4/C2H6 and C3H6/C3H8 ratios with significantly high amounts of olefins adsorbed. The best sorbent was CuCl/TiO2-PILC which showed a C2H4/C2H6 ratio of 5.3 and C3H6/C3H8 = 2.9 at 25 degrees C. In all cases, olefins adsorbed by pi-complexation with Cu(I) ion, reflected by heats of adsorption in the range 10.7-13.7 kcal/mol, as compared to 4.8-6.9 kcal/mol for the physical adsorption of the paraffins. The pi-complexation was fully reversible, limited only by the rates of pore diffusion. Diffusion of C-2's was rapid while for C-3's the diffusion reached 60% completion in approximately 6 min. Comparing these results with those of CuCl/gamma-Al2O3, the olefin/paraffin adsorption ratios were not as high as those of the later. However, the olefin isotherms on the PILC-supported CuCl displayed the desirable feature of having a steeper portion above the knee of the isotherm (the knee occurred at below 0.1 atm). This was a useful feature for separation because it yielded a larger working capacity. The steeper isotherm was attributed to a higher degree of energy heterogeneity as the PILC contained both surfaces of pillars and clay layers as opposed to only gamma-Al2O3.
