Equilibrium and advanced kinetic studies of CO2, CH4, and N2 adsorption on ZSM-5

Abstract Gas adsorption kinetics can significantly affect column size as well as the purity and recovery of products obtained from adsorption-based separation processes. Therefore, accurate adsorption kinetics are essential for designing pressure swing adsorption (PSA) processes. To obtain reliable kinetic parameters, it is crucial to employ reliable measurement methods and efficient yet accurate data evaluation procedures. In this study, we measured the equilibrium and kinetic data for CO 2, CH 4 , N 2 on ZSM-5 at three temperatures at pressures up to 120 kPa using a commercial volumetric-based system to evaluate the adsorbent’s potential for natural gas upgrading. The equilibrium data were analysed by fitting them to Langmuir equations with CH 4 /N 2 and CO 2 /CH 4 selectivities evaluated using the ideal adsorbed solution theory (IAST). A robust and efficient procedure to extract kinetic parameters using the non-isothermal Fickian diffusion (FD) model was developed. This procedure standardises the method for determining the actual start time of the adsorption for each kinetic measurement and for estimating initial guesses for all involved parameters. The goodness of data regression was evaluated by analysing sorted residual plots of the experimental and regressed data, as well as the uncertainties of the extracted parameters. By applying the procedure, kinetic parameters for gases on ZSM-5 were assessed. Results indicate that ZSM-5 exhibits favourable adsorption kinetics and equilibrium characteristics for CH₄/N₂ separation.