Elaboration d'une stratégie pour évaluer le potentiel de nouveaux matériaux poreux pour la séparation des gaz par adsorption.

Les Metal-Organic Framework (MOF) sont des adsorbants très prometteurs pour la séparation des gaz. Formés de centres métalliques reliés par des ligands organiques, ces matériaux présentent une structure organisée avec des pores de taille contrôlée ainsi que des surfaces et des volumes poreux très élevées. La possibilité de faire varier à la fois le centre métallique et le ligand organique donne aux MOFs une très grande diversité qu'on ne retrouve pas chez les zéolithes et les charbons actifs.L'objectif de cette étude a été d'évaluer le potentiel des MOFs en tant qu'adsorbants pour quatre procédés de séparation de gaz. En raison du grand nombre de MOFs disponibles, il a été nécessaire d'élaborer une stratégie pour identifier les matériaux les plus prometteurs dans chaque cas. Cette méthodologie comprend quatre étapes : une étape de criblage, une étape expérimentale, une étape de calcul et une étape d'évaluation.Pour l'étape de criblage, un nouvel appareil dit « à haut débit » a été développé pour mesurer des isothermes approximatives. Ensuite, un certain nombre de matériaux ont été retenus pour faire une étude plus approfondie de leurs propriétés d'adsorption. Des isothermes très précises ont été mesurées par gravimétrie tandis que les enthalpies d'adsorption ont été obtenues par microcalorimétrie. Dans l'étape de calcul, le modèle IAST a été utilisée pour prédire les sélectivités à partir des données en gaz pur. Enfin, les adsorbants ont été classés à l'aide d'un nouveau paramètre de sélection qui regroupe la sélectivité, la capacité efficace et l'enthalpie d'adsorption, où l'importance de chacun des paramètres peut être ajustée en fonction des besoins du procédé.Metal-Organic Frameworks (MOFs) are seen to be one of the most promising classes of adsorbents for gas separations. Consisting of metal clusters connected by organic linkers to form a fully crystalline network, these materials have record breaking surface areas and pore volumes as well as a wide variety of pore structures and sizes. This, coupled with the possibility to use virtually any transition metal as well as functionalized linkers, gives MOFs the chemical and physical versatility often lacking in traditional adsorbents such as zeolites and activated carbons.The purpose of this study was to evaluate the potential of MOFs as adsorbents for four gas separations of interest to the petrochemical industry. Because of the diversity and number of MOFs available, a methodology was needed to help identify the most promising materials in each case. The proposed methodology comprises four stages: a screening step, an experimental step, a computational step and finally an evaluation step. For the first stage, a high-throughput setup was developed to measure rough adsorption isotherms. A number of materials were then selected for a more thorough investigation of their adsorption properties. Highly accurate isotherms were measured gravimetrically while precise adsorption enthalpies were obtained by microcalorimetry. Step three involved predicting the co-adsorption behaviour from the pure gas isotherms using the Ideal Adsorbed Solution Theory. Finally, the adsorbents were ranked based on a new selection parameter regrouping selectivity, working capacity and adsorption enthalpy where the importance of each term can be adjusted depending on the requirements of the process

Elaboration d'une stratégie pour évaluer le potentiel de nouveaux matériaux poreux pour la séparation des gaz par adsorption.

Les Metal-Organic Framework (MOF) sont des adsorbants très prometteurs pour la séparation des gaz. Formés de centres métalliques reliés par des ligands organiques, ces matériaux présentent une structure organisée avec des pores de taille contrôlée ainsi que des surfaces et des volumes poreux très élevées. La possibilité de faire varier à la fois le centre métallique et le ligand organique donne aux MOFs une très grande diversité qu'on ne retrouve pas chez les zéolithes et les charbons actifs.L'objectif de cette étude a été d'évaluer le potentiel des MOFs en tant qu'adsorbants pour quatre procédés de séparation de gaz. En raison du grand nombre de MOFs disponibles, il a été nécessaire d'élaborer une stratégie pour identifier les matériaux les plus prometteurs dans chaque cas. Cette méthodologie comprend quatre étapes : une étape de criblage, une étape expérimentale, une étape de calcul et une étape d'évaluation.Pour l'étape de criblage, un nouvel appareil dit à haut débit a été développé pour mesurer des isothermes approximatives. Ensuite, un certain nombre de matériaux ont été retenus pour faire une étude plus approfondie de leurs propriétés d'adsorption. Des isothermes très précises ont été mesurées par gravimétrie tandis que les enthalpies d'adsorption ont été obtenues par microcalorimétrie. Dans l'étape de calcul, le modèle IAST a été utilisée pour prédire les sélectivités à partir des données en gaz pur. Enfin, les adsorbants ont été classés à l'aide d'un nouveau paramètre de sélection qui regroupe la sélectivité, la capacité efficace et l'enthalpie d'adsorption, où l'importance de chacun des paramètres peut être ajustée en fonction des besoins du procédé.Metal-Organic Frameworks (MOFs) are seen to be one of the most promising classes of adsorbents for gas separations. Consisting of metal clusters connected by organic linkers to form a fully crystalline network, these materials have record breaking surface areas and pore volumes as well as a wide variety of pore structures and sizes. This, coupled with the possibility to use virtually any transition metal as well as functionalized linkers, gives MOFs the chemical and physical versatility often lacking in traditional adsorbents such as zeolites and activated carbons.The purpose of this study was to evaluate the potential of MOFs as adsorbents for four gas separations of interest to the petrochemical industry. Because of the diversity and number of MOFs available, a methodology was needed to help identify the most promising materials in each case. The proposed methodology comprises four stages: a screening step, an experimental step, a computational step and finally an evaluation step. For the first stage, a high-throughput setup was developed to measure rough adsorption isotherms. A number of materials were then selected for a more thorough investigation of their adsorption properties. Highly accurate isotherms were measured gravimetrically while precise adsorption enthalpies were obtained by microcalorimetry. Step three involved predicting the co-adsorption behaviour from the pure gas isotherms using the Ideal Adsorbed Solution Theory. Finally, the adsorbents were ranked based on a new selection parameter regrouping selectivity, working capacity and adsorption enthalpy where the importance of each term can be adjusted depending on the requirements of the process.AIX-MARSEILLE1-BU Sci.St Charles (130552104) / SudocSudocFranceF

Functionalizing porous zirconium terephthalate UiO-66(Zr) for natural gas upgrading: A computational exploration

International audienceThe ligand functionalization effect on the CO2/CH4 separation performance of the MOF type UiO-66(Zr) was explored computationally. The -SO3H and -CO2H functionalized forms show the highest selectivity, good working capacity and medium ranged CO2 adsorption enthalpy that make these materials very promising for physisorption-based processes

Understanding the Thermodynamic and Kinetic Behavior of the CO2/CH4 Gas Mixture within the Porous Zirconium Terephthalate UiO-66(Zr): A Joint Experimental and Modeling Approach

International audienceA combination of experimental (gravimetry, microcalorimetry, and quasi-elastic neutron scattering) measurements and molecular modeling was employed to understand the coadsorption of CO2 and CH4 in the zirconium terephthalate UiO-66(Zr) material from both the thermodynamic and kinetic points of view. It was shown that each type of molecules adsorb preferentially in two different porosities of the material, that is, while CO2 occupy the tetrahedral cages, CH4 are pushed to the octahedral cages. Further, a very unusual dynamic behavior was also pointed out with the slower molecule, that is, CO2, enhancing the mobility of the fast one, that is, CH4, that contrasts with those usually observed so far for the CO2/CH4 mixture in narrow window zeolites where the molecules are most commonly diffusing independently or slowing-down the partner species. Such behavior was interpreted in light of molecular simulations that evidenced a jump type mechanism involving a tetrahedral cages-octahedral cages-tetrahedral cages sequence that occurs more frequently for CH4 when in presence of CO2. The consequences in terms of CO2/CH4 selectivity and the possible use of this MOF-type material in a PSA process are then discussed. It is thus clearly emphasized that this MOF material combines several favorable features including a good selectivity, high working capacity, and potential easy regenerability that make it as a good alternative candidate of the conventional NaX Faujasite used in pressure swing adsorption

An Adsorbent Performance Indicator as a First Step Evaluation of Novel Sorbents for Gas Separations: Application to Metal–Organic Frameworks

An adsorbent performance indicator (API) is proposed in an effort to initially highlight porous materials of potential interest for PSA separation processes. This expression takes into account working capacities, selectivities, and adsorption energies and additionally uses weighting factors to reflect the specific requirements of a given process. To demonstrate the applicability of the API, we have performed the adsorption of carbon dioxide and methane at room temperature on a number of metal–organic frameworks, a zeolite and a molecular sieve carbon. The API is calculated for two different CO₂/CH₄ separation case scenarios: “bulk separation” and “natural gas purification”. This comparison highlights how the API can be more versatile than previously proposed comparison factors for an initial indication of potential adsorbent performance

CH4 storage and CO2 capture in highly porous zirconium oxide based metal-organic frameworks

International audienc

Infrared study of the influence of reducible iron(III) metal sites on the adsorption of CO, CO2, propane, propene and propyne in the mesoporous metal-organic framework MIL-100

International audienceThe present study illustrates the importance of the oxidation state of iron within the mesoporous iron trimesate [\Fe3O(H2O)(2)F-0.81(OH)(0.19)\\C6H3(CO2)(3)\(2)] denoted MIL-100(Fe) (MIL = Material from Institut Lavoisier) during adsorption of molecules that can interact with the accessible metal sites through p-back donation. Adsorption of CO has been first followed by FTIR spectroscopy to quantify the Lewis acid sites in the dehydrated Fe(III) sample, outgassed at 150 degrees C, and on the partially reduced Fe(II/III), outgassed at 250 degrees C. The exposure of MIL-100(Fe) to CO2, propane, propene and propyne has then been studied by FTIR spectroscopy and microcalorimetry. It appears that p-back donating molecules are strongly adsorbed on reduced iron(II) sites despite the weaker Lewis acidity of cus Fe2+ sites compared to that of Fe3+ ones, as shown by pyridine adsorption

Infrared study of the influence of reducible iron(III) metal sites on the adsorption of CO, CO2, propane, propene and propyne in the mesoporous metal-organic framework MIL-100

International audienceThe present study illustrates the importance of the oxidation state of iron within the mesoporous iron trimesate [\Fe3O(H2O)(2)F-0.81(OH)(0.19)\\C6H3(CO2)(3)\(2)] denoted MIL-100(Fe) (MIL = Material from Institut Lavoisier) during adsorption of molecules that can interact with the accessible metal sites through p-back donation. Adsorption of CO has been first followed by FTIR spectroscopy to quantify the Lewis acid sites in the dehydrated Fe(III) sample, outgassed at 150 degrees C, and on the partially reduced Fe(II/III), outgassed at 250 degrees C. The exposure of MIL-100(Fe) to CO2, propane, propene and propyne has then been studied by FTIR spectroscopy and microcalorimetry. It appears that p-back donating molecules are strongly adsorbed on reduced iron(II) sites despite the weaker Lewis acidity of cus Fe2+ sites compared to that of Fe3+ ones, as shown by pyridine adsorption

Infrared study of the influence of reducible iron(III) metal sites on the adsorption of CO, CO2, propane, propene and propyne in the mesoporous metal-organic framework MIL-100

International audienceThe present study illustrates the importance of the oxidation state of iron within the mesoporous iron trimesate [\Fe3O(H2O)(2)F-0.81(OH)(0.19)\\C6H3(CO2)(3)\(2)] denoted MIL-100(Fe) (MIL = Material from Institut Lavoisier) during adsorption of molecules that can interact with the accessible metal sites through p-back donation. Adsorption of CO has been first followed by FTIR spectroscopy to quantify the Lewis acid sites in the dehydrated Fe(III) sample, outgassed at 150 degrees C, and on the partially reduced Fe(II/III), outgassed at 250 degrees C. The exposure of MIL-100(Fe) to CO2, propane, propene and propyne has then been studied by FTIR spectroscopy and microcalorimetry. It appears that p-back donating molecules are strongly adsorbed on reduced iron(II) sites despite the weaker Lewis acidity of cus Fe2+ sites compared to that of Fe3+ ones, as shown by pyridine adsorption

Adsorption and Diffusion of Light Hydrocarbons in UiO-66(Zr): A Combination of Experimental and Modeling Tools

SSCI-VIDE+ATARI+JGA:HJOInternational audienc