Tuning the PCP-SAFT equation of state to estimate adsorption-desorption hysteresis of pure fluids and mixtures confined in ordered mesoporous silica

Abstract

This study presents a comprehensive model for predicting the capillary condensation-evaporation hysteresis of pure components and mixtures in nanoporous materials, by tuning the dispersion energy parameter of the perturbed-chain polar statistical associating fluid theory (PCP-SAFT) equation of state. The model is based on an extensive hysteresis dataset comprising 304 data points for 24 different components, including nonpolar, polar, and associating components. The dispersion energy parameters for both adsorption and desorption processes are determined, and new correlations are proposed to improve the accuracy of the capillary condensation and evaporation pressure predictions. The results indicate that the current model provides superior prediction accuracy, with average absolute relative deviation (AARD) values of 10.89 % for the capillary condensation pressure and 10.95 % for evaporation pressure in pure components. The study also examines the effects of pore size, temperature, and fluid interactions on the capillary condensation-evaporation hysteresis. The model demonstrates good agreement with experimental data for both pure components and mixtures, under varying temperatures and pore sizes. The findings highlight the critical role of pore size and temperature in determining the extent of hysteresis. Stronger hysteresis is observed at specific pore diameters, particularly around a ratio of the sorbent mean pore radius to the PCP-SAFT segment size (r_p/σ) of 15–17, and at lower temperatures. The study concludes that the model provides a reliable framework for predicting the capillary condensation-evaporation behavior in nanoporous materials, with potential applications in various fields such as gas storage, separation processes, and environmental applications.