Nonisothermal Pore Diffusion Model for a Kinetically Controlled Pressure Swing Adsorption Process

A nonisothermal micropore diffusion model has been developed to simulate kinetically controlled pressure swing adsorption (PSA) processes: In this model, a dual site Langmuir isotherm represents adsorption equilibrium and rnicropore diffusivity depends on adsorbate concentration in the solid phase according to the chemical potential gradient as the driving force for diffusion. The model has been validated with published experimental data for the kinetically controlled separation of propylene/propane on 4A zeolite. Its performance has also been extensively compared with that of a bilinear driving force (bi-LDF) model for the same system. The results clearly show that a nonisothermal micropore diffusion model with concentration-dependent diffusivity is comprehensive and complete for kinetically selective systems. The conditions under which the bi-LDF model predictions may significantly deviate from those of the pore diffusion model have also been discussed.