Two characteristic properties of zeolites make it difficult to develop kernels for characterization: the replacement of Si atoms by Al in the structure, represented by the Si/Al ratio, and the exchange capacity of compensating cations. These two features result in a considerably high number of isotherm variations. We suggest a consistent characterization methodology based on pore type distribution, in order to overcome these obstacles. For demonstration purposes, we applied the methodology to the LTA family of zeolites (Lucena et al., LTA Zeolite Characterization Based on Pore Type Distribution, Ind. Eng. Chem. Res. 61 (5), 2268-2279, 2022).
The method is based on the investigation of the different energy levels that exist in the LTA supercages, where the experimental LTA isotherm can be approximated by a combination of the local isotherms of the supercages, thus, we can determine the distribution of pore types (PTD) associated with the LTA.
This kernel (LTA_CO2) consists of a collection of 8 local isotherms corresponding to each existing LTA cavity. These local isotherms should be interpreted as possible energy states of the LTA zeolite supercages.
The kernel, applied to any experimental isotherm of LTA, returns with the best volume combination of the cavities that are classified in 3 different energy levels (strong, moderate and weak interaction).
Experimental CO2 isotherms at 273 K of your LTA sample can be submitted here and we will return (by email), with a file containing the relevant information.
Relevant Definitions
Cages in the LTA: A, B, C, D, E, F, G
| Cavity Identified by Energy | |
| Low energy | A B D |
| Medium energy | E H C |
| High energy | F G |
Kernel_LTACO2: The kernel of local adsorption isotherms was calculated for each cage in the LTA a set of 8 cages.
Adsorption Isotherm Experimental: The relation, at constant temperature, between the amount adsorbed and the equilibrium pressure(Rouquerol, F., Rouquerol, J., Sing 1999). Pressure (kPa) — Adsorbed amount (cm3/g)
Adsorption isotherm model: Fitting gas adsorption data from Monte Carlo simulation data. Pressure (kPa) — Adsorbed amount (mmol/g)
PTD (Pore Type Distribution) (cm3/g): The pore structure of porous materials.The PTD is computationally determined through the deconvolution of a kernel of simulated isotherms using an experimental probe-gas isotherm.
Total pore volume (cm3/g): Volume of pores determined by stated method experimental or from simulated data.
Number of cavities: The types of cavities and the number of these cavities (across the volume) is the result of the PTD (pore type distribution). The calculation of the number supercages of the PTD was calculated based on the effective volumes (supercage effective volume = total volume/8).
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