Efficient Method To Obtain the Force Field for CO2 Adsorption on Zeolite 13X: Understanding the Host-Guest Interaction Mechanisms of Low-Pressure Adsorption

The current force fields used in grand canonical Monte Carlo (GCMC) simulations are frequently found to underestimate the low-pressure adsorption of CO, on zeolite 13X, which is crucial for engineering applications, including air prepurification and carbon capture from air. In this paper, a series of GCMC simulations are performed with a cation-free 13X model to study the influence of the force field parameters for host-guest interaction pairs on low-pressure adsorption. The unique effects of the equilibrium diameters of the interaction pairs on loading under low pressures are studied, and these effects are classified as one of three affecting modes according to their relative value for the interatomic distance of the interaction pair. Based on these results, six possible trends for a low-pressure adsorption isotherm with a changing equilibrium diameter are predicted. By revealing the different affecting modes caused by the microstructure of the host-guest interaction, the particular effects of the interaction pairs are explained. An efficient method to obtain the force field is thus proposed to develop a more accurate force field for low-pressure adsorption. The obtained force field is validated by comparing its results to experimental loading and isosteric heat data from the literature and by performing adsorption experiments in NaX with different Si/A1 ratios.