LTA Zeolite Characterization Based on Pore Type Distribution

Abstract

Despite the great industrial importance of zeolite LTA, there is still a gap in characterization methods, based on adsorption related to hindered diffusion of standard probe gases, such as N2 and Ar. LTA has a three-dimensional porous structure with a high degree of symmetry; however, variations in the location of cations, notably S2 and S3 sites, lead to different energy levels in supercages. Herein, we propose to extend the pore type distribution (PTD) methodology, recently applied for metal–organic frameworks, to zeolite materials. As an application example, we selected Na-LTA (4A) zeolite. Structural properties accessed by molecular simulation methods combined with experimental adsorption isotherms of CO2 at 273 K determine the individual contribution of supercages, with different energy levels, to the total adsorption uptake. Using eight local isotherms from the supercages, we developed a kernel that estimates the most likely energy distribution levels among supercages from the best fits of experimental isotherms. The method was applied in detail for LTA samples synthesized in laboratory and supplied by an industrial manufacturer. As an extension of the approach, we also analyze the use of the average local isotherm in the determination of imperfections found in the synthesis of LTA from unconventional raw materials or its deactivation in industrial processes. The proposed methodology generates detailed and relevant information not accessed by existing methods and allows the use of adsorption to characterize this class of very small pore sieves.

Mechanically stable polymer molecular sieve membranes with switchable functionality designed for high CO 2 separation performance

“…Despite their high separation performance, the chemically driven molecular sieves had a relatively small amount of pore volume compared to other types of molecular sieves ( 30 , 31 ). This indicates that certain portion of the membrane retained its original polymeric nature.…”

Potential Energy Surface-Based Descriptors for Nanoporous Materials and its Applications to Classification and CO2 Gas Adsorption into Zeolites

“…104 Two recent works attempt to model/predict the heat of adsorption of CO 2 on LTA4A (with Si/Al = 1) structures combining the distribution of adsorbed CO 2 on different adsorption sites upon loading with their specific energy 105 or by using the pore type distribution to model adsorption isotherms from a list of pore types of supercages containing different Na distributions. 106 Unfortunately, neither approach has been extended to different Si/Al ratios and has the same drawback of using only one fixed Al distribution (a problem inherent to small system sizes used in molecular simulations) and does not use any ML model. We realize that there is a place for testing the applicability of new descriptors able to predict the heat of adsorption of CO 2 on both pure siliceous and ion-exchanged zeolites as a function of the ratio of occupancy of aluminum atoms over the T-sites [Al/(Si + Al)].…”

“…We can cite the work of Chehaibou et al using ML thermodynamic perturbation theory to predict heat of adsorption of CH 4 and CO 2 on siliceous and protonated chabazite . Two recent works attempt to model/predict the heat of adsorption of CO 2 on LTA4A (with Si/Al = 1) structures combining the distribution of adsorbed CO 2 on different adsorption sites upon loading with their specific energy or by using the pore type distribution to model adsorption isotherms from a list of pore types of supercages containing different Na distributions . Unfortunately, neither approach has been extended to different Si/Al ratios and has the same drawback of using only one fixed Al distribution (a problem inherent to small system sizes used in molecular simulations) and does not use any ML model.…”

Adsorption of CO2 Using “Sugar Cube”-Shaped Zeolite A Type Derived from Thermally Treated Kaolin and NaOH

“…Zeolites are distinguished as one of the most significant classes of porous materials. The porous nature of zeolite offers a significant surface area which affects the absorbing power of zeolitic materials, and having materials with a variable Si/Al ratio is an added advantage, which makes them suitable adsorbents for a variety of applications. , Zeolites are generally known as hydrated aluminosilicates with three-dimensional tetrahedral TO 4 (T = Si or Al) connected through oxygen atoms with alkali or alkaline earth metal cations. The aluminosilicates in the tetrahedral framework structure can produce porous structures with a wide range of cavities and channels that have dimensions up to 2 nm.…”