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.

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. © 2020 Society of Chemical Industry

We present in this paper a study of water adsorption behavior in confined media by using on the one hand a Non-Local Density Functional Theory (NLDFT) coupled with the SAFT-VR equation of state and, on the other hand, Grand Canonical Monte-Carlo (GCMC) molecular simulations. The present work is a second step in an ongoing NLDFT/SAFT-VR coupling. The first step has focused on the monomer contribution and especially in the way to extend the dispersive terms of the monomer contribution of SAFT-VR in the NLDFT formalism. In the present work, the theory has been extended by introducing the associative contribution due to hydrogen bonding and is applied to water, which is modeled as one sphere with four identical associating sites placed in a tetrahedral geometry with the same interaction parameters for both theory and simulations. NLDFT/SAFT-VR and GCMC results for density distributions of water in graphitic slit-like micropores and mesopores are shown to be in good agreement. Moreover, the capillary condensation and evaporation were investigated with the theoretical model in micro and mesopores, and also in the case of activated surfaces.