Multiscale Adsorption and Transport in Porous Materials
Hierarchical porous materials, combining multiple porosities, are widely used in industry (adsorption, separation, catalysis) to overcome slow diffusion in microporous solids (< 2 nm) and increase access to their large surface area. The benefits of combining porosities by adding meso (2-50 nm) and macro (> 50 nm) pores to microporosity have been demonstrated, but engineering these solids, which are heterogeneous in size, shape, and connectivity, still relies on «trial and error« strategies. Existing design approaches, even when based on physical foundations, are limited to empirical parameters that cannot be derived from molecular adsorption/transport coefficients. This project aims to develop a bottom-up model of adsorption and transport in multiscale porous materials by coupling experiment, molecular simulation and theory. This multiscale strategy will provide a comprehensive framework of adsorption/transport in porous media to allow the design of optimal samples for a given application based on parameters accessible from simple experiments.
Through the use of theoretical and experimental methods applied to hierarchical solids with controlled properties, our model will enable the design of optimal adsorbents for process intensification. Molecular approaches, at the heart of this project, will allow to overcome the barriers that have prevented the emergence of a multiscale formalism: invalidity of hydrodynamics at ~nm scale, adsorption/transport coupling. The strengths of this project are: (1) Use of solids with controlled porosities, morphologies, etc. obtained by pseudomorphic synthesis. (2) Experimental/theoretical study of adsorption/transport in hierarchical solids (pulsed field gradient NMR, chromatography, molecular simulation, etc.). (3) Rigorous scaling via Statistical Mechanics to connect molecular parameters to engineering parameters without losing the smallest scale information.
Our project led to a novel synthesis route of macroporous (pores up to 20 µm) monoliths made up of zeolite (micropores ~0,8 nm) nanocrystals (200 nm) allowing to intensify the processes by increasing the adsorption capacities in flow and by increasing the adsorption kinetics thanks to the creation of mesoporosity between the nanocrystals. FAU-X monoliths have been successfully used for the trapping of Cs, one of the principal contaminants of radioactive waters coming from nuclear disaster (Fukushima).
As we progressed, new questions arose and new avenues were opened to us. Thus, in parallel to our major achievements, typically the establishment of a synthesis of hierarchical porous monoliths, this project deserves to be continued further downstream. In particular, some researchers involved in the TAMTAM project are pursuing their efforts in the development of these materials and their applications.
We have developed a synthesis route for hierarchical nanoporous (zeolitic) solids that could have an impact in many fields such as phase separation, catalysis, etc. With the help of these solids, the understanding obtained by combining experiment/theory has allowed us to identify the parameters controlling the adsorption and the transport of fluids in their hierarchical porosity. This knowledge allows to consider - after further studies - the development of a rational design of this new class of materials. The TAMTAM project has led to 16 scientific papers in international journals (6 in preparation). The work resulting from this consortium working around the multi-scale adsorption and transport of nanoconfined fluids has been presented at 13 national and international conferences.
Hierarchical porous materials, which combine several porosity scales, are widely used in industry (adsorption, separation, catalysis) to overcome slow diffusion in microporous solids (< 2 nm) and enhance access to their large surface area. The benefits of combining porosities by adding meso (2-50 nm) and macro (> 50 nm) pores to the existing microporosity was demonstrated but engineering of such solids, which are heterogeneous in size, shape, and connectivity, still relies on trial and error strategies. Available modeling approaches, even when based on a physical ground, are limited to empirical parameters which cannot be derived from molecular adsorption/transport coefficients. In particular, none of the existing approaches offers the ground for a bottom up model of adsorption/transport in multiscale materials as (1) they only describe empirically the interplay between adsorption and transport, (2) they do not account for the breakdown of hydrodynamics at the nm scale, and (3) they are not multiscale in nature.
This project aims at developing a bottom up model of adsorption/transport in multiscale porous materials using experiment, molecular simulation and theory. This multiscale strategy will provide a unifying and comprehensive framework of adsorption and transport in porous media to design optimized samples for a given application based on a minimum set of parameters available from simple experiments. These samples will be synthesized and tested to further validate our novel framework. Thanks to the use of Statistical Mechanics and adsorption, NMR and chromatography experiments for hierarchical solids with controlled properties (synthesized on-demand), this model will allow the design of optimal adsorbents to achieve process intensification. The use of molecular approaches, at the heart of this project, allows bypassing the barriers that have hampered the development of a multiscale framework: hydrodynamics breakdown at the nm scale, adsorption/transport coupling and upscaling over scales. The strengths of this proposal, which rely on the solid know-how of the partners, are as follows. (1) Use of well-defined materials with controlled porosities, morphologies, chemistries, etc. obtained using pseudomorphic syntheses. This allows studying adsorption/transport at each synthesis step (macropores, macropores + mesopores, macropores + micropores, macropores + mesopores + micropores). (2) Joint experimental/theoretical study of adsorption/transport in hierarchical solids (Pulsed Field Gradient NMR, chromatography, molecular simulation, etc.). (3) Rigorous Statistical Mechanics upscaling to connect parameters from molecular to engineering scales without losing information at the lower scale. Owing to the use of data that capture the many adsorption/transport regimes upon varying pressure, pore size, etc., this approach does not rely on hydrodynamics and, hence, does not require assuming a given adsorption/flow type.
This multidisciplinary project combines experimental/theoretical skills that will lead to a paradigm shift needed to tackle a great industrial challenge: Rational design of hierarchical materials for filtration and phase separation. Of particular relevance for the DEFI 3, this project will stimulate a new deal for industrial separation (propylene/propane and CO2/CH4), purification (ethanol dehydration, H2 purification), and capture (CO2 but also MeOH and NH3 from gaseous effluents), etc. Fundamental and practical breakthroughs will be achieved: (1) Extend recent developments from nanofluidics to complex problems of adsorption/transport in multiscale media, (2) Develop a novel framework to rationally design adsorbents for adsorption and filtration using simple structural and textural parameters. (3) Use the wealth of unexploited nanoscale phenomena (slippage, non-linearity in transport induced by the adsorption/dynamics interplay, etc.) to improve the adsorbent efficiency.
Monsieur Benoit COASNE (Laboratoire Interdisciplinaire de Physique (UMR5588))
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
Université Pierre et Marie Curie / UPMC Chimie de la Matière Condensée de Paris (UMR7574)
CNRS DR12_MADIREL Centre National de la Recherche Scientifique délégation Provence et Corse_Matériaux Divisés, Interfaces, Réactivité et Electrochimie (UMR7246)
ICGM Institut Charles Gerhardt Montpellier (UMR 5253 CNRS/UM/ENSCM), Equipe Matériaux Avancés pour la Catalyse et la Santé
LIPHY Laboratoire Interdisciplinaire de Physique (UMR5588)
Help of the ANR 466,956 euros
Beginning and duration of the scientific project: September 2015 - 48 Months