This study presents a performance-driven approach to the optimization of 3D-printed monoliths based on 13X zeolite, obtained through Direct Ink Writing, aimed at carbon capture applications. The research compares three formulations using different binders - polyvinyl alcohol, sodium alginate, bentonite - evaluating their influence on printability, mechanical strength, and CO2 capture performance. A comprehensive set of characterizations revealed the formulation-structure-performance relationships of the produced monoliths. A multi-criteria index was developed to rank the monoliths performance, highlighting the importance of tailoring ink composition to specific application requirements. Polyvinyl alcohol-based samples preserved the highest adsorption capacity but suffered from poor mechanical strength, while bentonite-based samples exhibited excellent structural integrity but lower diffusion performance. A fourth formulation obtained by using both alginate and bentonite showed the best compromise among all the properties studied. The proposed strategy enables rational design of 3D-printable materials for gas separation technologies and beyond.

We introduce a new computational procedure called PoLA (Porosity Local Analysis), a point-by-point description of the void space in nanoporous materials that surpasses the conventional representation of pores as homogeneous regions of regular geometry (spheres, cylinders, slits). Each volume element is assigned its own porous character through the minimum distance to opposite walls (MinD), a quantity directly linked to the host-guest interaction potential and therefore to physisorption behaviour. We apply PoLA to a dataset of 109 atomistic carbon models and correlate the resulting V(MinD) distributions with N2 and H2 adsorption isotherms at 77 K, simulated by Grand Canonical Monte Carlo. A purpose-built machine learning procedure, based on optimized neural networks, infers V(MinD) from a nitrogen isotherm and predicts the corresponding hydrogen uptake. Validation against four commercial activated carbons (Norit Row, Maxsorb, BAX1700, CGF4) shows excellent agreement between predicted and measured H2 isotherms up to 60 bar, demonstrating that PoLA provides both a transferable porosity descriptor and a predictive tool for adsorbent design.

This paper reports the results of an international interlaboratory study sponsored by the Versailles Project on Advanced Materials and Standards (VAMAS) and led by the National Institute of Standards and Technology (NIST) on the measurement of low-pressure CO2 adsorption isotherms at 25 °C on zeolite 13X (NIST research grade test material 10257). Eighteen laboratories participated in the study and contributed 21 datasets. From these data, a consensus reference isotherm, along with the 95

The random motion (the diffusion) of guest molecules in nanoporous host materials is key to their manifold technological applications and, simultaneously, a ubiquitous phenomenon in nature quite in general. Based on a specification of the different conditions under which molecular diffusion in nanoporous materials may occur and of the thus resulting relevant parameters, a survey of the various ways of the measurement of the determining parameters is given. Starting with a condensed introduction to the respective measuring principles, the survey notably includes a summary of the various parameters accessible by each individual technique, jointly with an overview of their strengths and weaknesses as well as of the respective ranges of observation. The presentation is complemented by basic relations of diffusion theory and molecular modeling in nanoporous materials, illustrating their significance for enhancing the informative value of each measuring technique and the added value attainable by their combination. By providing guidelines for the measurement and reporting of diffusion properties of chemical compounds in nanopores, the document aims to contribute to the clarification and standardization of the presentation, nomenclature, and methodology associated with the documentation of diffusion phenomena in nanoporous materials serving for catalytic, mass separation, and other relevant purposes.

The Redlich-Peterson isotherm is widely used in liquid phase adsorption studies but the combination with the Ideal Adsorbed Solution Theory is hampered by the fact that an analytical expression for the reduced grand potential does not exist in the range of low pressures or concentrations. In this contribution we demonstrate an efficient approach to approximate the reduced grand potential using a Padé approximant allowing to perform the calculations with the Fast-IAS algorithm leading to execution times that are slightly slower but comparable to a dual site Langmuir/Fast-IAS combination. While the non-autonomous initial value approach remains a simpler method for this isotherm, the proposed method is recommended when execution times have to be minimized.

The measurement of accurate nitrogen adsorption kinetics in state-of-the-art LiLSX beads is essential for the optimization of vacuum swing processes for the production of oxygen. A novel methodology is presented in order to establish experimentally the presence of combined heat and mass transfer phenomena. The very rapid uptake kinetics are measured using the adsorption differential volumetric apparatus and interpreted using a nonisothermal model. The novel methodology includes the determination of all the physical parameters of the model from the simultaneous regression of all experimental runs at different pressure levels. The approach has been demonstrated on two Zeochem binderless LiLSX beaded samples, for which traditional methods proved inconclusive, allowing to determine the relative kinetic performance.

Semicrystalline polyamides (PAs) are optimal materials to develop high-pressure resistant liners for type IV hydrogen storage tanks due to a favorable combination of barrier performance, mechanical resistance, and lightness. However, experimental data on hydrogen transport in PAs are incomplete or inconsistent, and usually do not report separately the contributions of solubility and diffusivity, hence limiting a deep understanding of the permeation mechanism and its dependence on the material structure. Moreover, recent developments have led to the design of modified polyamides which could better serve the high-pressure storage applications. In this work, the hydrogen barrier performance of Polyamide 6 (PA6), Polyamide 11 (PA11) and an impact-modified PA 6 (PA6-I), was evaluated and the results obtained with different techniques and on different samples compared. Permeation measurements were performed in constant-volume and constant-pressure apparatuses at different temperatures and pressures, on different samples of each material. Sorption measurements were carried out into a differential sorption system. Results from the permeation and sorption devices were compared against each other and with literature data, allowing to understand the effect of various factors. The H2 2 solubility in PA is mostly affected by density, as a lower free volume of the amorphous phase leads to a lower gas uptake. On the other hand, diffusivity and, consequently, permeability, are also strongly affected by the morphology of the crystal phase, which depends on the production protocol. In most of the cases inspected, the discrepancy between data from different experimental techniques or literature works can be explained by the different crystal morphology of the samples used in the test. Temperature enhances diffusivity, permeability and solubility, while the pressure reduces the permeability, as it lowers the free volume, and increases the activation energy of permeation. An estimation of the minimum thickness required to meet high-pressure storage technical guidelines was provided for the case of PA6-I.

Mass transport in nanoporous materials is a key property that allows to improve the performance of many gas separation processes and design more efficient heterogeneous catalytic reactors. In many instances a combination of surface resistance and internal diffusion are present. The combined model for surface barrier and diffusion in a ZLC system is discussed in detail and the analytical solutions valid for the traditional and the partial loading experiments have been derived for the spherical and slab geometries. The model reduces to the limiting forms of pure diffusion when kR_p/D>100 , and pure surface barrier when kR_p/D<1 . This study has shown that most literature studies have analysed ZLC responses incorrectly based on an effective combined dimensionless parameter. Two methods are described to obtain the parameters from the long-time asymptotic behaviour of the response curves. Both approaches have been demonstrated on curves generated from the full model solution and experimental data on an etched sample of Y zeolite. Both the analysis of the model and of the experimental results confirm that to characterize combined surface barriers and diffusion one should perform at least experiments at two different flowrates where the system is kinetically controlled, and crucially a partial loading experiment with a time to the switch which should be at least an order of magnitude smaller than the smallest of the diffusion and surface barrier times.

Reference gas adsorption isotherms are useful for validating equilibrium data obtained from various techniques and for ensuring that experimental systems are operating correctly. In this work, we extend an interlaboratory study on a NIST reference zeolite (Na-Y, RM8850) to two additional temperatures above and below the original 298.15 K, validating the results via independent measurements using two different techniques. Volumetric experiments on a novel Adsorption Differential Volumetric Apparatus (ADVA-270) were carried out at The University of Edinburgh, and gravimetric experiments were performed at Hiden Isochema using a proprietary XEMIS microbalance. Both techniques provided highly accurate results and an excellent match between the two independent measurements using less than 150 mg of sample. Absolute equilibrium data were modelled using a Langmuir-virial isotherm to obtain an accurate concentration dependence of the heat of adsorption.

Global warming is an ever-rising environmental concern, and carbon dioxide (CO2) is among its major causes. Different technologies, including adsorption, cryogenic separation, and sequestration, have been developed for CO2 separation and storage/utilization. Among these, carbon capture using nano-adsorbents has the advantages of excellent CO2 separation and storage performance as well as superior heat- and mass-transfer characteristics due to their large surface area and pore volume. In this work, an environmentally friendly, facile, bottom-up synthesis of ZIF-8 hollow nanospheres (with reduced chemical consumption) was developed for selective CO2 separation and storage. During this soft-templating synthesis, a combined effect of ultra-sonication and low-temperature hydrothermal synthesis showed better control over an oil-in-water microemulsion formation and the subsequent growth of large-surface-area hollow ZIF-8 nanospheres having excellent particle size distribution. Systematic studies on the synthesis parameters were also performed to achieve fine-tuning of the ZIF-8 crystallinity, hollow structures, and sphere size. The optimized hollow ZIF-8 nanosphere sample having uniform size distribution exhibited remarkable CO2 adsorption capability (∼2.24 mmol g-1 at 0 °C and 1.75 bar), a CO2/N2 separation selectivity of 12.15, a good CO2 storage capacity (1.5-1.75 wt %), and an excellent cyclic adsorption/desorption performance (up to four CO2 adsorption/desorption cycles) at 25 °C. In addition, the samples showed exceptional structural stability with only ∼15% of overall weight loss up to 600 °C under a nitrogen environment. Therefore, the hollow ZIF-8 nanospheres as well as their highly controlled soft-templating synthesis method reported in this work are useful in the course of the development of nanomaterials with optimized properties for future CO2 capture technologies.

The ZLC technique is a powerful technique for the measurement of diffusion in nanoporous materials using mg quantities of a sample. Questions remain on whether the measured properties are representative of larger samples. A methodology has been developed to carry out single pellet experiments to determine average properties and variability of equilibrium and kinetic properties. To demonstrate the approach, n ‐pentane on HISIV3000 extrudates was used as the test system, which was shown to be macropore diffusion controlled. Results on nine pellets provided average values showing a perfect match to breakthrough column experiments with a sample two orders of magnitudes larger.

This paper reports the results of an international interlaboratory study sponsored by the Versailles Project on Advanced Materials and Standards (VAMAS) and led by the National Institute of Standards and Technology (NIST) on the measurement of water vapor sorption isotherms at 25 °C on a pelletized nanoporous carbon (BAM-P109, a certified reference material). Thirteen laboratories participated in the study and contributed nine pure water vapor isotherms and four relative humidity isotherms, using nitrogen as the carrier gas. From these data, reference isotherms, along with the 95% uncertainty interval ( U k=2 ), were determined and are reported in a tabular format.

Water/AQSOA-FAM-Z02 adsorption equilibrium data have been measured using two gravimetric systems at 30 degrees C, 50 degrees C, and 70 degrees C in the range 1-90% relative humidity (RH). The data were found to conform to a type IV adsorption isotherm and have been correlated with the Rigid Adsorbent Lattice Fluid dual site model in the range 1-50% RH, which has been shown to reproduce the experimental results with an average absolute deviation in line with uncertainties measured from duplicate and replicate experiments. The adsorption and desorption data were found not to overlap even at 1% RH, resulting in an open hysteresis under the experimental conditions studied. The Rigid Adsorbent Lattice Fluid dual site model adapted to take into account a nondesorbing fraction of pores reproduced the experimental desorption curves providing an overall description of the system for use in adsorption process simulations. The isosteric heats of adsorption obtained show a complex concentration dependence with a local maximum (84.2 kJ mol-1) and minimum (55.8 kJ mol-1) which are values consistent with the ranges found in the literature.

An optimized Friedel-Crafts based methodology used to prepare high surface area and pore volume hyper-cross-linked polymers (HCPs) is presented here. A significant reduction in catalyst quantities resulted in an HCP showing SSABET of 905 m(2)/g and total pore volume of asymptotic to 1.12 cm(3)/g. Spectroscopic investigations (DR-FTIR and SS-NMR) reveal that lowering the amount of catalyst avoid uncontrolled reaction pathways. For the optimized material, CO2 uptakes are 2.55 mmol/g at 273 K and 1 bar. High pressure measurements at 298 K resulted in the uptake of 7.33 mmol/g of CO(2 )at 24 bar and 3.84 mmol/g of CH4 at 42 bar.

In all silica-gel adsorption processes driven by low-grade heat, the kinetics of adsorption of water on silica-gel is very important in order to optimize design and becomes an essential factor in ultra-low grade heat applications. A new approach for the determination of the mass transfer coefficient of water in commercial silica-gel is proposed and demonstrated with measurements on a single particle using the zero length column technique. Under equilibrium conditions the methodology offers the key advantage to acquire equilibrium isotherms with thousands of points in less than one day. This allows to obtain the relationship between vapour concentration and equilibrium adsorbed amount through numerical interpolation. At higher flowrates, the system operates under kinetic control therefore allowing the determination of the mass transfer coefficient. The novel approach calculates all the elements needed to obtain the mass transfer coefficient from the measured signals without the need to use a specific model. Adsorption and desorption experiments were carried out at different flowrates and three different temperatures. The kinetic responses can be used to determine an average mass transfer coefficient, which is consistent with literature values, but a complex behaviour is observed with surface diffusion as the main contribution to the transport process.

A novel adsorption differential volumetric apparatus was developed for the determination of diffusional time constants in nanoporous materials and applied to diffusion of nitrogen and argon in commercial pellets of 4A zeolite. The system is designed for high rates of data acquisition allowing to determine mass transfer time constants of seconds over the pressure range from vacuum to 130 kPa. Diffusion of N-2 and Ar on a single pellet and fragments obtained from the pellet are studied between -10 degrees C and 35 degrees and 0.8 to 55 kPa. These systems are chosen as representing weak adsorption to demonstrate the sensitivity of the apparatus that gives a good signal-to-noise ratio even with a single pellet in the entire pressure range. The systems studied confirm micropore diffusion control and an isothermal diffusion model was shown to reproduce accurately the observed kinetics using reduced pressure plots. As the crystal size in the pellet is not known accurately, the resulting activation energies and the ratio of diffusional time constants of N-2 and Ar were used to validate the results against known literature values.

The SARS-CoV-2 virus is primarily transmitted through virus-laden fluid particles ejected from the mouth of infected people. Face covers can mitigate the risk of virus transmission but their outward effectiveness is not fully ascertained. Objective: by using a background oriented schlieren technique, we aim to investigate the air flow ejected by a person while quietly and heavily breathing, while coughing, and with different face covers. Results: we found that all face covers without an outlet valve reduce the front flow through by at least 63% and perhaps as high as 86% if the unfiltered cough jet distance was resolved to the anticipated maximum distance of 2-3 m. However, surgical and handmade masks, and face shields, generate significant leakage jets that may present major hazards. Conclusions: the effectiveness of the masks should mostly be considered based on the generation of secondary jets rather than on the ability to mitigate the front throughflow.