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D Nicholson - One of the best experts on this subject based on the ideXlab platform.

  • Henry Constant of water adsorption on functionalized graphite importance of the potential models of water and functional group
    Journal of Physical Chemistry C, 2018
    Co-Authors: Yonghong Zeng, Toshihide Horikawa, D Nicholson
    Abstract:

    We present a theoretical study of the Henry Constant for water adsorbed on graphite decorated with functional groups at the edges of the graphene layers. A general expression for the Henry Constant...

  • a coherent definition of Henry Constant and isosteric heat at zero loading for adsorption in solids an absolute accessible volume
    Chemical Engineering Journal, 2018
    Co-Authors: Luisa Prasetyo, D Nicholson
    Abstract:

    Abstract We present a new analysis of the Henry’s law Constant and isosteric heat at zero coverage for gas adsorption on solid surfaces, which removes the ambiguities inherent in earlier definitions (Do et al., 2008). A new definition of accessible volume ensures physical self-consistency between these two properties. We show that an earlier definition of accessible volume, as the volume within which the adsorbate-adsorbent potential energy is non-positive, is too restrictive because it neglects the penetration of molecules with large kinetic energies into the highly repulsive (positive) regions of the potential, which occurs more frequently at higher temperatures. The new definition has been tested for a number of adsorbents, and for a wide range of adsorbates commonly used in the characterization of porous solids. In particular, we have highlighted the differences between the old and new definitions of the Henry Constant and the isosteric heat at zero loading. Our analysis also reveals that, contrary to a common assumption made in the adsorption literature, the van’t Hoff plot is non-linear, and linearity is only satisfied over a narrow range of temperature.

  • Henry Constant and isosteric heat at zero loading for gas adsorption in carbon nanotubes
    Physical Chemistry Chemical Physics, 2008
    Co-Authors: Atichat Wongkoblap, D Nicholson
    Abstract:

    The Henry Constant and the isosteric heat of adsorption at zero loading in a carbon nanotube bundle are studied with Monte Carlo integration for the adsorption of gases over a range of temperatures. The spacing between nanotubes in a bundle is determined from the minimization of potential energy of interaction between these tubes. We study different tube configurations with bundles of 2, 3, 4 and 7 tubes. Depending on the configuration it is found that the spacing is of between 0.31 to 0.333 nm, and this falls within the range reported in the literature. The Henry Constant has been carefully defined so that it will not become negative at high temperatures. This is done with the aid of accessible volume, rather than the usual absolute void volume. We show that linearity of the van’t Hoff plot for the Henry Constant is not strictly followed. Furthermore the slope of this plot is not equal to the isosteric heat of adsorption at zero loading, which is found to be a strong function of temperature. From the results we find that the Henry Constant and the heat of adsorption depend on the tube configuration. In general the adsorption in the cusp interstices is strongest followed by that inside the tube and finally on the outer surface. However for very small tubes adsorption occurs inside the tube first. For molecules with orientation, the behaviour is even more interesting and the shape of the isosteric heat versus temperature depends on the degree of orientation, tube configuration and the domain of adsorption (interstices, inside the tube and on the outer surface).

  • on the Henry Constant and isosteric heat at zero loading in gas phase adsorption
    Journal of Colloid and Interface Science, 2008
    Co-Authors: D Nicholson
    Abstract:

    The Henry Constant and the isosteric heat of adsorption at zero loading are commonly used as indicators of the strength of the affinity of an adsorbate for a solid adsorbent. It is assumed that (i) they are observable in practice, (ii) the Van Hoff's plot of the logarithm of the Henry Constant versus the inverse of temperature is always linear and the slope is equal to the heat of adsorption, and (iii) the isosteric heat of adsorption at zero loading is either Constant or weakly dependent on temperature. We show in this paper that none of these three points is necessarily correct, first because these variables might not be observable since they are outside the range of measurability; second that the linearity of the Van Hoff plot breaks down at very high temperature, and third that the isosteric heat versus loading is a strong function of temperature. We demonstrate these points using Monte Carlo integration and Monte Carlo simulation of adsorption of various gases on a graphite surface. Another issue concerning the Henry Constant is related to the way the adsorption excess is defined. The most commonly used equation is the one that assumes that the void volume is the volume extended all the way to a boundary passing through the centres of the outermost solid atoms. With this definition the Henry Constant can become negative at high temperatures. Although adsorption at these temperatures may not be practical because of the very low value of the Henry Constant, it is more useful to define the Henry Constant in such a way that it is always positive at all temperatures. Here we propose the use of the accessible volume; the volume probed by the adsorbate when it is in nonpositive regions of the potential, to calculate the Henry Constant.

Vlugt T.j.h. - One of the best experts on this subject based on the ideXlab platform.

  • Computation of gas solubilities in choline chloride urea and choline chloride ethylene glycol deep eutectic solvents using Monte Carlo simulations
    'Elsevier BV', 2020
    Co-Authors: Seyed Salehi H., Hens R., Moultos O., Vlugt T.j.h.
    Abstract:

    Deep eutectic solvents (DESs) are considered as green alternatives to room temperature ionic liquids (RTILs), due to their lower-cost synthesis and more environmentally friendly nature. In this work, Monte Carlo (MC) simulations have been used to compute the solubilities of CO2, H2S, CH4, CO, H2, and N2 in choline chloride urea (ChClU) and choline chloride ethylene glycol (ChClEg) DESs. Due to the strong intermolecular interactions of DESs, leading to high viscosities, MC simulations present significant challenges with respect to system equilibration and solute molecule insertions. The Continuous Fractional Component Monte Carlo (CFCMC) method has been used with our open-source code, Brick-CFCMC, to improve molecule insertions and equilibration of the system, and directly compute the excess chemical potential and solubility (in terms of the Henry Constant) of the gas molecules in the DESs. Pure DES properties, such as density and radial distribution functions (RDFs), were well reproduced by MC simulations. The solubilities of gases were, however, underestimated by the CFCMC simulations compared to available experimental data from literature. The order of solubilities of the different gases in ChClU at 328 K was obtained as H2S > CO2 > CH4 > H2 > CO > N2, which reasonably agrees with experimental data from literature. The OPLS force field resulted in larger average Henry Constants in ChClEg, compared to the GAFF force field, implying the better suitability of the GAFF force field for the calculations. Smaller ionic charge scaling factors were shown to increase the solubilities of the gases in the DESs, but result in lower densities. The differences between the computed Henry Constants from MC simulations and experimental data from literature may be caused by the unsuitability of the used force field parameters of the DESs in combination with those of the solute gases. Nonetheless, experimental data from literature is scarce (except for CO2) and in some cases contradictory, which makes the comparison with the computational results difficult.Engineering Thermodynamic

  • Computation of gas solubilities in choline chloride urea and choline chloride ethylene glycol deep eutectic solvents using Monte Carlo simulations
    'Elsevier BV', 2020
    Co-Authors: Seyed Salehi H., Hens R., Moultos O., Vlugt T.j.h.
    Abstract:

    Deep eutectic solvents (DESs) are considered as green alternatives to room temperature ionic liquids (RTILs), due to their lower-cost synthesis and more environmentally friendly nature. In this work, Monte Carlo (MC) simulations have been used to compute the solubilities of CO2, H2S, CH4, CO, H2, and N2 in choline chloride urea (ChClU) and choline chloride ethylene glycol (ChClEg) DESs. Due to the strong intermolecular interactions of DESs, leading to high viscosities, MC simulations present significant challenges with respect to system equilibration and solute molecule insertions. The Continuous Fractional Component Monte Carlo (CFCMC) method has been used with our open-source code, Brick-CFCMC, to improve molecule insertions and equilibration of the system, and directly compute the excess chemical potential and solubility (in terms of the Henry Constant) of the gas molecules in the DESs. Pure DES properties, such as density and radial distribution functions (RDFs), were well reproduced by MC simulations. The solubilities of gases were, however, underestimated by the CFCMC simulations compared to available experimental data from literature. The order of solubilities of the different gases in ChClU at 328 K was obtained as H2S > CO2 > CH4 > H2 > CO > N2, which reasonably agrees with experimental data from literature. The OPLS force field resulted in larger average Henry Constants in ChClEg, compared to the GAFF force field, implying the better suitability of the GAFF force field for the calculations. Smaller ionic charge scaling factors were shown to increase the solubilities of the gases in the DESs, but result in lower densities. The differences between the computed Henry Constants from MC simulations and experimental data from literature may be caused by the unsuitability of the used force field parameters of the DESs in combination with those of the solute gases. Nonetheless, experimental data from literature is scarce (except for CO2) and in some cases contradictory, which makes the comparison with the computational results difficult.

Philip L Llewellyn - One of the best experts on this subject based on the ideXlab platform.

  • screening the effect of water vapour on gas adsorption performance application to co2 capture from flue gas in metal organic frameworks
    Chemsuschem, 2017
    Co-Authors: Nicolas Chanut, Sandrine Bourrelly, B Kuchta, Christian Serre, Jongsan Chang, Paul A Wright, Philip L Llewellyn
    Abstract:

    A simple laboratory-scale protocol that enables the evaluation of the effect of adsorbed water on CO2 uptake is proposed. 45 metal–organic frameworks (MOFs) were compared against reference zeolites and active carbons. It is possible to classify materials with different trends in CO2 uptake with varying amounts of pre-adsorbed water, including cases in which an increase in CO2 uptake is observed for samples with a given amount of pre-adsorbed water. Comparing loss in CO2 uptake between “wet” and “dry” samples with the Henry Constant calculated from the water adsorption isotherm results in a semi-logarithmic trend for the majority of samples allowing predictions to be made. Outliers from this trend may be of particular interest and an explanation for the behaviour for each of the outliers is proposed. This thus leads to propositions for designing or choosing MOFs for CO2 capture in applications where humidity is present.

Christian Serre - One of the best experts on this subject based on the ideXlab platform.

  • screening the effect of water vapour on gas adsorption performance application to co2 capture from flue gas in metal organic frameworks
    Chemsuschem, 2017
    Co-Authors: Nicolas Chanut, Sandrine Bourrelly, B Kuchta, Christian Serre, Jongsan Chang, Paul A Wright, Philip L Llewellyn
    Abstract:

    A simple laboratory-scale protocol that enables the evaluation of the effect of adsorbed water on CO2 uptake is proposed. 45 metal–organic frameworks (MOFs) were compared against reference zeolites and active carbons. It is possible to classify materials with different trends in CO2 uptake with varying amounts of pre-adsorbed water, including cases in which an increase in CO2 uptake is observed for samples with a given amount of pre-adsorbed water. Comparing loss in CO2 uptake between “wet” and “dry” samples with the Henry Constant calculated from the water adsorption isotherm results in a semi-logarithmic trend for the majority of samples allowing predictions to be made. Outliers from this trend may be of particular interest and an explanation for the behaviour for each of the outliers is proposed. This thus leads to propositions for designing or choosing MOFs for CO2 capture in applications where humidity is present.

Karel Aim - One of the best experts on this subject based on the ideXlab platform.

  • analysis of Henry s Constant for carbon dioxide in water via monte carlo simulation
    Fluid Phase Equilibria, 2004
    Co-Authors: Martin Lisal, William R Smith, Karel Aim
    Abstract:

    We present calculations of the Henry Constant for carbon dioxide in water by Monte Carlo simulations over a broad range of temperatures, from 0 ◦ C to the critical temperature of water. A range of intermolecular potential models is examined for each species. Carbon dioxide is modelled by two three-site (EPM2, and Errington and Panagiotopoulos) potentials and water is modelled by four three-site (SPC, SPC/E, MSPC/E, and Errington and Panagiotopoulos) potentials, by the four-site TIP4P potential and by the five-site TIP5P potential. Henry’s Constant is computed via the Widom test-particle insertion method and by means of a staged free-energy perturbation method. The performance of the various potential models with respect to the accuracy of their prediction of the Henry Constant is discussed. The staged free-energy perturbation method, employed at several representative temperatures, allows further analysis of the Henry Constant with respect to the free energy of cavity formation for hosting the CO2 solute molecule in the H2O solvent and the free energy of interactions between the CO2 solute molecule and the H2O solvent. We found that all CO2/H2O models predicted a qualitatively correct temperature dependence of the Henry Constant but only the Errington and Panagiotopoulos CO2/H2O model gave values for the Henry Constant in reasonable agreement with experimental data. © 2004 Elsevier B.V. All rights reserved.