A Strong Test of Atomically Detailed Models of Molecular Adsorption in Zeolites Using Multilaboratory Experimental Data for CO₂ Adsorption in Ammonium ZSM-5

Abstract

Institute of Standards (NIST) reported CO 2 adsorption isotherms measured independently by 11 groups on reference material RM 8852, an ammonium ZSM-5 zeolite. Good reproducibility and high reliability of this experimental data provide a strong test for the ability of atomically detailed models to predict adsorption of CO 2 in zeolites. We developed force fields for CO 2 in ammonium zeolites based on first-principles calculations and also independently performed experiments with RM 8852 by microcalorimetry. At low pressures good agreement was obtained between predictions and experiments. At high pressures, however, deviations were observed. We show that the charge-balancing cations in the experimental material are the predominant source of the discrepancy between simulation and experiment at high pressures; the experimental sample treatment causes deammoniation. In addition, accounting for a small amount of noncrystalline mesoporosity in the zeolite brings predictions into much better agreement with experiments.

Measurement and interpretation of unary supercritical gas adsorption isotherms in micro-mesoporous solids

“…activated carbons), which feature pores across the entire spectrum of sizes. As such, they also represent important reference materials for the textural characterisation of industrial adsorbents by physisorption [8] and for the development of rigorous models with predictive ability at high pressures [12].…”

Performance-Based Screening of Porous Materials for Carbon Capture

“… 301 One important feature of these force fields is that they can be developed completely from first-principles and independent of any experimental data, while at the same time being able to accurately reproduce experimental measurements of adsorption isotherms and heats of adsorption. 299 , 301 …”

A reference high-pressure CH4 adsorption isotherm for zeolite Y: results of an interlaboratory study

“…Evaluation of the experimental details indicated the activation protocol was not followed for one case (DS 14), which could explain the lower uptake. The importance of following the activation protocol was explicitly highlighted in ILS1 (Nguyen et al 2018), and modeling work based on the CO 2 /ZSM-5 reference data underscored that varying the pretreatment temperature of ammonium ZSM-5 affects what cations are in the zeolite (Fang et al 2020).…”

“…The output was, for the first time, high-pressure adsorption reference data using a reference material. The CO 2 /ZSM-5 reference isotherm recently proved helpful for advancing modeling methods (Fang et al 2020). Having companion high-pressure isotherm experiments showing high-quality results for a reference material would also be valuable to demonstrate reliability in high-pressure experiments on new adsorbents, particularly given the large number of porous materials that have not been replicated since they were first reported (Agrawal et al 2020).…”

“…ZY (RM 8850) is completely microporous (see Fig. S1), whereas ZSM-5 (RM 8852) has a small amount of mesoporosity (Fang et al 2020). ZY being a different material from ZSM-5 would also allow the true extent of the usefulness of the CO 2 /ZSM-5 reference isotherm to be determined when applied to measurements of other materials, as would be expected in real-world applications.…”