Diffusion kinetics of ethane, ethylene, and their binary mixtures in ethane-selective adsorbents

Sorption kinetics of single component and binary mixtures of ethane and ethylene in powder and pellet samples of paraffin-selective adsorbents Ni(bdc)(ted)(0.5) and ZIF-7 were investigated by zero-length column (ZLC) technique for the purpose of olefin/paraffin separation. The intracrystalline diffusivities were determined at 25 degrees C and the results were compared in order to investigate the effects of coadsorption for binary gas mixtures and also diffusion in pelletized adsorbents. The diffusion time constants measured for ethane and ethylene through both ZIF-7 and Ni(bdc)(ted)(0.5) in powder and pellet forms were similar and found to be in the ranges of 2.68-3.35 x 10(-3) s(-1) and 1.23-4.07 x 10(-3) s(-1), respectively, for single component and binary mixtures. Furthermore, diffusion of ethylene for both single component and binary mixture trials revealed the presence of surface resistance due to strong interactions between the C-C double bond and the external crystalline surface of the adsorbents. The findings of this study provide novel kinetic characterizations on paraffin-selective adsorbents for the separation of ethane and ethylene.