Density functional theory for the description of spherical non-associating monomers in confined media using the SAFT-VR equation of state and weighted density approximations

As a first step of an ongoing study of thermodynamic properties and adsorption of complex fluids in confined media, we present a new theoretical description for spherical monomers using the Statistical Associating Fluid Theory for potential of Variable Range (SAFT-VR) and a Non-Local Density Functional Theory (NLDFT) with Weighted Density Approximations (WDA). The well-known Modified Fundamental Measure Theory is used to describe the inhomogeneous hard-sphere contribution as a reference for the monomer and two WDA approaches are developed for the dispersive terms from the high-temperature Barker and Henderson perturbation expansion. The first approach extends the dispersive contributions using the scalar and vector weighted densities introduced in the Fundamental Measure Theory (FMT) and the second one uses a coarse-grained (CG) approach with a unique weighted density. To test the accuracy of this new NLDFT/SAFT-VR coupling, the two versions of the theoretical model are compared with Grand Canonical Monte Carlo (GCMC) molecular simulations using the same molecular model. Only the version with the “CG” approach for the dispersive terms provides results in excellent agreement with GCMC calculations in a wide range of conditions while the “FMT” extension version gives a good representation solely at low pressures. Hence, the “CG” version of the theoretical model is used to reproduce methane adsorption isotherms in a Carbon Molecular Sieve and compared with experimental data after a characterization of the material. The whole results show an excellent agreement between modeling and experiments. Thus, through a complete and consistent comparison both with molecular simulations and with experimental data, the NLDFT/SAFT-VR theory has been validated for the description of monomers.This work was sponsored by the ERC advanced grant Failflow (27769). This financial support is gratefully acknowledged. This work was supported by Acción Integrada España-Francia from Ministerio de Ciencia e Innovación and Picasso Project (Project Nos. FR2009-0056 and PHC PI- CASSO2010). F.J.B. would like to acknowledge financial support from Ministerio de Ciencia e Innovación (Project No. FIS2010-14866), Junta de Andalucía, and Universidad de Huelva. C. Malheiro would like to acknowledge the ISIFOR Carnot institute for her mobility grant

Exploring the Potential of Metal–Organic Frameworks for the Separation of Blends of Fluorinated Gases with High Global Warming Potential

Funding Information: The authors acknowledge the financial support from the LIFE‐4‐Fgases project, LIFE20 CCM/ES/001748, funded by EU LIFE Programme. This work was also financed by national funds from FCT/MCTES (Portugal) through Associate Laboratory for Green Chemistry–LAQV (UIDB/50006/2020 | UIDP/50006/2020), the contracts of Individual Call to Scientific Employment Stimulus 2020.00835.CEECIND (J.M.M.A.)/2021.01432.CEECIND (A.B.P.), and the Norma Transitória DL 57/2016 Program Contract (R.P.P.L.R.). Publisher Copyright: © 2022 The Authors. Global Challenges published by Wiley-VCH GmbH.The research on porous materials for the selective capture of fluorinated gases (F-gases) is key to reduce their emissions. Here, the adsorption of difluoromethane (R-32), pentafluoroethane (R-125), and 1,1,1,2-tetrafluoroethane (R-134a) is studied in four metal–organic frameworks (MOFs: Cu-benzene-1,3,5-tricarboxylate, zeolitic imidazolate framework-8, MOF-177, and MIL-53(Al)) and in one zeolite (ZSM-5) with the aim to develop technologies for the efficient capture and separation of high global warming potential blends containing these gases. Single-component sorption equilibria of the pure gases are measured at three temperatures (283.15, 303.15, and 323.15 K) by gravimetry and correlated using the Tóth and Virial adsorption models, and selectivities toward R-410A and R-407F are determined by ideal adsorption solution theory. While at lower pressures, R-125 and R-134a are preferentially adsorbed in all materials, at higher pressures there is no selectivity, or it is shifted toward the adsorption R-32. Furthermore, at high pressures, MOF-177 shows the highest adsorption capacity for the three F-gases. The results presented here show that the utilization of MOFs, as tailored made materials, is promising for the development of new approaches for the selective capture of F-gases and for the separation of blends of these gases, which are used in commercial refrigeration.publishersversionepub_ahead_of_prin

Adsorption of gas/water systems in confined media : DFT/SAFT modelling coupling to an experimental study

La compréhension des phénomènes d’adsorption de gaz en présence d’eau dans des milieux confinés est une problématique importante tant d’un point de vue fondamental que du point de vue des applications industrielles Les travaux menés dans cette thèse ont principalement porté sur le développement d’un nouveau couplage NLDFT/SAFT-VR (Non-Local Density Functional Theory/ Statistical Associating Fluid Theory for potentials of Variable Range) pour modéliser les propriétés interfaciales et l’adsorption de méthane, d’eau et de leur mélange en milieu confiné. Les résultats théoriques obtenus sur ces fluides ont été comparés avec succès à des calculs de simulation moléculaire. Par ailleurs, des isothermes d’adsorption expérimentales de méthane et d’eau sur des charbons actifs ont été mesurées par la technique gravimétrique sur une balance à suspension magnétique. Afin de pouvoir comparer les isothermes expérimentales et théoriques, il est nécessaire de connaître la distribution en taille de pore des solides poreux. C’est pourquoi un nouveau modèle thermodynamique de caractérisation des milieux microporeux a été développé. Les comparaisons des isothermes d’adsorption de méthane ont montré un excellent accord entre résultats théoriques et expérimentaux.Understanding the gas/water adsorption phenomena in confined media is an important issue from a fundamental point of view and for industrial applications. The main aim of this thesis was to develop a new NLDFT/SAFT-VR coupling (Non-Local Density Functional Theory/ Statistical Associating Fluid Theory for potentials of Variable Range) to model the interfacial properties and the adsorption of methane, water and their binary mixture in porous media. A successful comparison was found between theoretical results from this model and molecular simulation calculations. Moreover, experimental adsorption isotherms of methane and water were measured on activated carbons by gravimetric method on a magnetic suspension balance. In order to compare experimental and modeled adsorption isotherms, it is necessary to get the pore size distribution of the porous solids. To do this, a new thermodynamic model for the characterization of microporous media was developed. The comparison between adsorption isotherms of methane has shown an excellent agreement between theoretical results and experimental measurements

Imbibition of Liquid Helium in Aerogels

6 pagesInternational audienceWe report optical measurements of the imbibition of liquid helium in a sample of silica aerogel with 90 % porosity. Both direct imaging and light scattering experiments were performed to determine the dynamics and the properties of the liquid-gas interface in both the normal and superfluid phases of liquid helium. In the normal phase, a classical Lucas Washburn behavior is observed for the rise of the imbibition front while the behavior in the superfluid phase is markedly different, as the fluid invades the sample from all sides with a constant speed. In both phases, the interface is rough, leading to light scattering. In addition, condensation ahead of the imbibition front is observed at low temperature in the superfluid phase

Fracture, deformation, and fluid-solid coupled effects in porous quasi-brittle materials

International audienc

Adsorption of fluorinated greenhouse gases on activated carbons: evaluation of their potential for gas separation

Funding of the KET4F-Gas project, SOE2/P1/P0823, co-funded by the Interreg Sudoe Program through the European Regional Development Fund (ERDF). A.B. Pereiro and J.M.M. Araújo acknowledge FCT/MCTES for financial support through IF/00190/2014 contract and IF/00210/2014 contract, respectively. Rui Ribeiro acknowledges financial support through the Norma Transitória DL 57/2016 Program Contract (FCT/MCTES). This work was also supported by the Associate Laboratory for Green Chemistry ? LAQV, which is financed by national funds from FCT/MCTES (UID/QUI/50006/2019).Background: The increasing awareness of the release of fluorinated gases (F-gases) into the atmosphere is instigating the development of techniques to capture them from refrigerants. In this work, the adsorption of difluoromethane (R-32), pentafluoroethane (R-125), and 1,1,1,2-tetrafluoroethane (R-134a) on four different activated carbons (ACs) is studied. Additionally, the selectivity of the ACs for the components of commercial refrigerants, R-410A and R-407F, is evaluated. Results: The estimation of the density of the adsorbed phase as a function of temperature allows the experimental fractional loading of each F-gas on any of the ACs to be correlated as a temperature-independent function of its reduced pressure, which is described by Tóth or dual-site Langmuir equations or as an exponential function of the adsorption potential under the framework of the Adsorption Potential theory (APT). It is shown that the APT can be generalized with excellent accuracy to the systems studied if an adsorbate-dependent affinity coefficient is used as a shifting factor to bring the characteristic curves of all F-gases into a single one for each AC. R-32 is the F-gas most adsorbed by all adsorbents, followed by R-134a, and by R-125. All ACs are selective for R-125 in R-410A commercial refrigerants, especially at lower pressures. Additionally, all ACs are selective for R-125 and R-134a over R-32 in R407-F commercial refrigerant. Conclusion: The utilization of ACs for adsorption of the three most used F-gases is promising. By selecting ACs with different porous characteristics, it is possible to evaluate their influence on the selectivity for the components of different commercial refrigerants.authorsversionpublishe