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

Abstract

The current force fields used in grand canonical Monte Carlo (GCMC) simulations are frequently found to underestimate the low-pressure adsorption of CO 2 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 lowpressure 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/Al ratios.

Quantitatively Understanding the Insights into CO2 Adsorption on Faujasite from the Heterogeneity and Occupancy Sequence of Adsorption Sites

“…In each simulation, 1 × 10 5 MC cycles were used as production steps and an additional 1 × 10 5 MC cycles were used as equilibrium steps (an MC cycle is a series of steps defined in RASPA). These settings produced accurate results for CO 2 adsorption on faujasite zeolite in our previous study …”

“…These settings produced accurate results for CO 2 adsorption on faujasite zeolite in our previous study. 57 l…”

Quantifying Impact of Intrinsic Flexibility on Molecular Adsorption in Zeolites

“…Previous studies have shown that the adsorption in cationic zeolites is sensitive to the position of the cations within the zeolite during the simulation. − Figure shows that the accessible volume of silica LTA is very similar in flexible and rigid structures. We characterized the positions of the Na cations in the cationic material, finding no difference between the rigid and flexible structures within the uncertainty of our data (Table ).…”

A Transferable Force Field for Predicting Adsorption and Diffusion of Small Molecules in Alkali Metal Exchanged Zeolites with Coupled Cluster Accuracy

“…The accuracy of CCFF in predicting self-diffusivities was compared to experimental data in Figures – and also to predictions based on 14 previous force fields (see Table S12) from the literature − in Figures S20–S24 in the Supporting Information. The latter comparison between CCFF and literature force fields was done for CH 4 , CO 2 , and N 2 in Na-exchanged zeolite X/Y, and CO 2 and N 2 in 4A.…”