Maxwell–Stefan modeling of the separation of H2 and CO2 at high pressure in an MFI membrane

In the present study, a Maxwell–Stefan based model was developed for the separation of CO2 from H2 at high pressure in an MFI membrane. The usage of the Vignes interpolation formula for mixture surface diffusivities together with the IAST (ideal adsorbed solution theory) using bulk gas phase fugacities for mixture adsorption proved to be a feasible combination for this case. Both the effects of defects in the zeolite film and the mass transfer resistance caused by the support layers were studied and included in the model. Only pure component experimental data was used in the model building to predict the gas mixture permeation. The fitted diffusion parameters were in line with the literature values. The occupancy fraction dependence of CO2 surface diffusivity was utilized for the first time in the prediction of binary separation of H2/CO2 at high pressure on a real MFI membrane. Usage of an occupancy fraction dependence for CO2 surface diffusivity improved the model predictions. The adsorption parameter fitting for hydrogen based on the permeation measurements resulted in a feasible adsorption model, but should be used with caution. The model predicts binary separation measurement results relatively well. Both defects and support have a noticeable impact on the overall performance of the membrane.

► Separation of H2/CO2 was modeled with a Maxwell–Stefan based model.
► Occupancy dependence of CO2 diffusivity is applied on a real MFI membrane.
► Only pure component data is demanded to predict the binary separation behavior.
► Model includes both the defect and support effects on the gas permeation.
► Separation of H2 and CO2 with an MFI membrane is modeled at high pressure.