Separation of propylene/propane via pressure swing adsorption using SiCHA

Cryogenic distillation is the common method for separating propylene/propane mixtures, but this is highly energy intensive. Some 8-ring silica zeolites, especially pure silica chabazite (SiCHA), are known to show high kinetic selectivity for propylene over propane. In this work, we study the separation of propylene/propane using pure silica chabazite (SiCHA) in a simple 4-step pressure swing adsorption process. An isothermal isobaric micropore diffusion model has been developed to simulate this kinetically controlled separation. In this model, Langmuir isotherm represents adsorption equilibrium and micropore diffusivity depends on the adsorbate concentration in the solid phase with chemical potential gradient as the driving force. Since the diffusion of propane in SiCHA is extremely slow, equilibrium information for propane has been in direct by calculated using its uptake data at 353 K and 600 Torr.