Propylene/Propane Separation Using SiCHA

Separation of propylene/propane mixture with new 8-ring zeolite, pure silica chabazite (SiCHA), has been studied in this work. Since the diffusion of propane molecules in SiCHA is extremely slow, thus equilibrium information for propane has been indirectly estimated using available uptake data at 80 °C and 600 Torr. Moreover, molecular simulation has been used to obtain equilibrium information of propylene and propane and verify our estimation. The ideal kinetic selectivity of propylene/propane mixture is ∼28 at 80 °C, which increases with decreasing temperature. A four-step, kinetically controlled pressure swing adsorption process has been suggested for this separation and studied in detail using a nonisothermal micropore diffusion model, developed and verified in an earlier study. In this model, Langmuir isotherm represents adsorption equilibrium and micropore diffusivity depends on adsorbate concentration in the micropores, according to chemical potential gradient as the driving force for diffusion.