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Rigby SP. The Anatomy of Amorphous, Heterogeneous Catalyst Pellets. MATERIALS (BASEL, SWITZERLAND) 2023; 16:3205. [PMID: 37110038 PMCID: PMC10142278 DOI: 10.3390/ma16083205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 04/03/2023] [Accepted: 04/05/2023] [Indexed: 06/19/2023]
Abstract
This review focuses on disordered, or amorphous, porous heterogeneous catalysts, especially those in the forms of pellets and monoliths. It considers the structural characterisation and representation of the void space of these porous media. It discusses the latest developments in the determination of key void space descriptors, such as porosity, pore size, and tortuosity. In particular, it discusses the contributions that can be made by various imaging modalities in both direct and indirect characterisations and their limitations. The second part of the review considers the various types of representations of the void space of porous catalysts. It was found that these come in three main types, which are dependent on the level of idealisation of the representation and the final purpose of the model. It was found that the limitations on the resolution and field of view for direct imaging methods mean that hybrid methods, combined with indirect porosimetry methods that can bridge the many length scales of structural heterogeneity and provide more statistically representative parameters, deliver the best basis for model construction for understanding mass transport in highly heterogeneous media.
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Affiliation(s)
- Sean P. Rigby
- Department of Chemical and Environmental Engineering, Faculty of Engineering, University Park Campus, University of Nottingham, Nottingham NG7 2RD, UK;
- Geo-Energy Research Centre, University Park Campus, University of Nottingham, Nottingham NG7 2RD, UK
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2
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Kikkinides ES, Gkogkos G, Monson PA, Valiullin R. Connecting dynamic pore filling mechanisms with equilibrium and out of equilibrium configurations of fluids in nanopores. J Chem Phys 2022; 156:134702. [PMID: 35395874 DOI: 10.1063/5.0087249] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In the present study, using dynamic mean field theory complemented by grand canonical molecular dynamics simulations, we investigate the extent to which the density distributions encountered during the dynamics of capillary condensation are related to those distributions at equilibrium or metastable equilibrium in a system at fixed average density (canonical ensemble). We find that the states encountered can be categorized as out of equilibrium or quasi-equilibrium based on the magnitude of the driving force for mass transfer. More specifically, in open-ended slit pores, pore filling via double bridging is an out of equilibrium process, induced by the dynamics of the system, while pore filling by single bridge formation is connected to a series of configurations that are equilibrium configurations in the canonical ensemble and that cannot be observed experimentally by a standard adsorption process, corresponding to the grand canonical ensemble. Likewise, in closed cap slits, the formation of a liquid bridge near the pore opening and its subsequent growth while the initially detached meniscus from the capped end remains immobilized are out of equilibrium processes that occur at large driving forces. On the other hand, at small driving forces, there is a continuous acceleration of the detached meniscus from the capped end, which is associated with complete reversibility in the limit of an infinitesimally small driving force.
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Affiliation(s)
- E S Kikkinides
- Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - G Gkogkos
- Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - P A Monson
- Department of Chemical Engineering, University of Massachusetts, Amherst, Massachusetts 01003-9303, USA
| | - R Valiullin
- Faculty of Physics and Earth Sciences, Leipzig University, Leipzig, Germany
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3
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Ledezma Lopez GA, Verstraete JJ, Sorbier L, Glowska A, Leinekugel-Le-Cocq D, Jolimaitre E, Jallut C. Generation of γ-Alumina Digital Twins Using a Nitrogen Porosimetry Simulation. Ind Eng Chem Res 2021. [DOI: 10.1021/acs.iecr.1c02849] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gabriel Alejandro Ledezma Lopez
- IFP Energies Nouvelles, Rond-point de l’échangeur de Solaize, BP 3, 69360 Solaize, France
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, LAGEPP UMR 5007 43 boulevard du 11 novembre 1918, Villeurbanne, F-69100, France
| | - Jan J. Verstraete
- IFP Energies Nouvelles, Rond-point de l’échangeur de Solaize, BP 3, 69360 Solaize, France
| | - Loïc Sorbier
- IFP Energies Nouvelles, Rond-point de l’échangeur de Solaize, BP 3, 69360 Solaize, France
| | - Aleksandra Glowska
- IFP Energies Nouvelles, Rond-point de l’échangeur de Solaize, BP 3, 69360 Solaize, France
- Centre for Nature Inspired Engineering (CNIE), University College of London, Gower Street, London, WC1E6BT, United Kingdom
| | | | - Elsa Jolimaitre
- IFP Energies Nouvelles, Rond-point de l’échangeur de Solaize, BP 3, 69360 Solaize, France
| | - Christian Jallut
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, LAGEPP UMR 5007 43 boulevard du 11 novembre 1918, Villeurbanne, F-69100, France
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Bruschi L, Mistura G, Negri F, Coasne B, Mayamei Y, Lee W. Adsorption on alumina nanopores with conical shape. NANOSCALE 2018; 10:18300-18305. [PMID: 30246857 DOI: 10.1039/c8nr06265j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Adsorption on porous solids depends on the morphology of the pores, the cylindrical one being the most studied in the literature. In this work, we present the first experimental investigation of adsorption and evaporation on conical nanopores produced by anodization of aluminium oxide. The pores are about 50 μm long, with the wide ends having a diameter of ∼79 nm and the narrow ones of ∼30 nm. Three different pores configurations are considered: open at both ends, open only at the narrow end and open only at the wide end. Despite the very small value of the conical angle α, estimated to be ∼0.06°, just barely above α = 0° corresponding to a cylindrical pore, the adsorption isotherms look strikingly different from those measured on cylindrical pores of similar size. First of all, the hysteresis loops of the conical pores with two open ends and with open wide ends practically coincide. Furthermore, they are narrower and the adsorption and evaporation branches are broader than those of the cylindrical pores with similar size. Finally, conical pores with open narrow ends exhibit a large hysteresis indicative of pore blocking. To unravel the mechanisms underlying adsorption and evaporation in such conical pores, we also report complementary results obtained using on-lattice grand canonical Monte Carlo simulations.
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Affiliation(s)
- Lorenzo Bruschi
- Dipartimento di Fisica e Astronomia G. Galilei, Università di Padova, via Marzolo 8, 35131 Padova, Italy.
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5
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Mesoporous silica nanoparticles for enhanced lidocaine skin delivery. Int J Pharm 2018; 550:325-332. [DOI: 10.1016/j.ijpharm.2018.08.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 08/02/2018] [Accepted: 08/02/2018] [Indexed: 01/20/2023]
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6
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Bruschi L, Mistura G, Prasetyo L, Do DD, Dipalo M, De Angelis F. Adsorption on Nanopores of Different Cross Sections Made by Electron Beam Nanolithography. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:106-114. [PMID: 29211486 DOI: 10.1021/acs.langmuir.7b03695] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Adsorption on nanoporous matrices is characterized by a pronounced hysteresis loop in the adsorption isotherm, when the substrate is loaded and unloaded with adsorbate, the origin of which is a matter of immense debate in the literature. In this work, we report a study of argon adsorption at 85 K on nonconnecting nanopores with one end closed to the surrounding where the effects of different pore cross sections fabricated by electron beam lithography (EBL) are investigated. A polymethylmethacrylate (PMMA) resist is deposited on the electrodes of a sensitive quartz crystal microbalance without degradation of the resonance quality factor or the long-term and short-term stabilities of the device even at cryogenic temperatures. Four different pores' cross sections: circular, square, rectangular, and triangular, are produced from EBL, and the isotherms for these pore shapes exhibit pronounced hysteresis loops whose adsorption and desorption branches are nearly vertical and have almost the same slopes. No difference is observed in the hysteresis loops of the isotherms for the pores with triangular and square cross sections, whereas the hysteresis loop for the pore with circular cross sections is much narrower, suggesting that they are more regular than the other pores. All of these observations suggest that the hysteresis behavior resulted mainly from microscopic geometric irregularities present in these porous matrices.
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Affiliation(s)
- Lorenzo Bruschi
- Dipartimento di Fisica e Astronomia G. Galilei, Università di Padova , via Marzolo 8, 35131 Padova, Italy
| | - Giampaolo Mistura
- Dipartimento di Fisica e Astronomia G. Galilei, Università di Padova , via Marzolo 8, 35131 Padova, Italy
| | - Luisa Prasetyo
- School of Chemical Engineering, University of Queensland , St. Lucia, Queensland 4072, Australia
| | - Duong D Do
- School of Chemical Engineering, University of Queensland , St. Lucia, Queensland 4072, Australia
| | - Michele Dipalo
- Istituto Italiano di Tecnologia , via Morego 30, 16163 Genova, Italy
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7
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An R, Huang L, Mineart KP, Dong Y, Spontak RJ, Gubbins KE. Adhesion and friction in polymer films on solid substrates: conformal sites analysis and corresponding surface measurements. SOFT MATTER 2017; 13:3492-3505. [PMID: 28422244 DOI: 10.1039/c7sm00261k] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this work, we present a statistical mechanical analysis to elucidate the molecular-level factors responsible for the static and dynamic properties of polymer films. This analysis, which we term conformal sites theory, establishes that three dimensionless parameters play important roles in determining differences from bulk behavior for thin polymer films near to surfaces: a microscopic wetting parameter, αwx, defined as the ratio of polymer-substrate interaction to polymer-polymer interaction; a dimensionless film thickness, H*; and dimensionless temperature, T*. The parameter αwx introduced here provides a more fundamental measure of wetting than previous metrics, since it is defined in terms of intermolecular forces and the atomic structure of the substrate, and so is valid at the nanoscale for gas, liquid or solid films. To test this theoretical analysis, we also report atomic force microscopy measurements of the friction coefficient (μ), adhesion force (FA) and glass transition temperature (Tg) for thin films of two polymers, poly(methyl methacrylate) (PMMA) and polystyrene (PS), on two planar substrates, graphite and silica. Both the friction coefficient and the glass transition temperature are found to increase as the film thickness decreases, and this increase is more pronounced for the graphite than for the silica surface. The adhesion force is also greater for the graphite surface. The larger effects encountered for the graphite surface are attributed to the fact that the microscopic wetting parameter, αwx, is larger for graphite than for silica, indicating stronger attraction of polymer chains to the graphite surface.
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Affiliation(s)
- Rong An
- Herbert Gleiter Institute of Nanoscience, Nanjing University of Science & Technology, Nanjing 210094, P. R. China and Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA.
| | - Liangliang Huang
- School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, OK 73019, USA
| | - Kenneth P Mineart
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA.
| | - Yihui Dong
- State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing 210009, P. R. China
| | - Richard J Spontak
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA. and Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Keith E Gubbins
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA.
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8
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Bruschi L, Mistura G, Nguyen PTM, Do DD, Nicholson D, Park SJ, Lee W. Adsorption in alumina pores open at one and at both ends. NANOSCALE 2015; 7:2587-2596. [PMID: 25578390 DOI: 10.1039/c4nr06469k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We have studied adsorption in regular, self-ordered alumina pores open at both ends or only at one end. The straight, non-connected pores have diameters ranging from 22 to 83 nm, with a relative dispersion below 1% in the pore size. Adsorption isotherms measured in open pores with a torsional microbalance show pronounced hysteresis loops characterized by nearly vertical and parallel adsorption and desorption branches. Blocking one end of the pores with glue has a strong influence on adsorption, as expected from classical macroscopic arguments. However, the experimental measurements show an unexpectedly rich phenomenology dependent on the pore size. For large pores (Dp ≥ 67 nm), the isotherms for closed end pores present much narrower hysteresis loops whose adsorption and desorption boundaries envelop the desorption branches of the isotherms for the corresponding open pores of the same size. The loop for small closed end pores (Dp = 22 nm) is slightly wider than that for open pores while the adsorption branches coincide. For large pores, in contrast, the desorption branches of pores with the same Dp overlap regardless of the pore opening. These observations are in agreement with our grand canonical Monte Carlo (GCMC) simulations for a cylindrical pore model with constrictions, suggesting that the alumina pores could be modeled using a constricted pore model whose adsorption isotherm depends on the ratio of the constriction size to the pore size (Dc/Dp).
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9
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Suh D, Yasuoka K, Zeng XC. Molecular dynamics simulation of heterogeneous nucleation on nanotubes. RSC Adv 2015. [DOI: 10.1039/c5ra04398k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Condensation rate inside and outside the tube depends on the pore diameter and length.
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Affiliation(s)
- Donguk Suh
- Department of Mechanical Engineering
- Keio University
- Yokohama, Japan
| | - Kenji Yasuoka
- Department of Mechanical Engineering
- Keio University
- Yokohama, Japan
| | - Xiao Cheng Zeng
- Department of Chemistry
- University of Nebraska-Lincoln
- Lincoln, USA
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10
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11
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Nguyen VT, Do D, Nicholson D. Reconciliation of different simulation methods in the determination of the equilibrium branch for adsorption in pores. MOLECULAR SIMULATION 2014. [DOI: 10.1080/08927022.2013.829229] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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12
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Fan C, Do D, Nicholson D. On the existence of a hysteresis loop in open and closed end pores. MOLECULAR SIMULATION 2014. [DOI: 10.1080/08927022.2013.869805] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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13
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Continuous adsorption in highly ordered porous matrices made by nanolithography. Nat Commun 2013; 4:2966. [DOI: 10.1038/ncomms3966] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2013] [Accepted: 11/20/2013] [Indexed: 11/08/2022] Open
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14
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Malijevský A. Filling and wetting transitions at grooved substrates. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:445006. [PMID: 24067670 DOI: 10.1088/0953-8984/25/44/445006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The wetting and filling properties of a fluid adsorbed on a solid grooved substrate are studied by means of a microscopic density functional theory. The grooved substrates are modelled using a solid slab, interacting with the fluid particles via long-range dispersion forces, to which a one-dimensional array of infinitely long rectangular grooves is sculpted. By investigating the effect of the groove periodicity and the width of the grooves and the ridges, a rich variety of different wetting morphologies is found. In particular, we show that for a saturated ambient gas, the adsorbent can occur in one of four wetting states characterized by (i) empty grooves, (ii) filled grooves, (iii) a formation of mesoscopic hemispherical caps (iv) a macroscopically wet surface. The character of the transition between particular regimes, that also extend off-coexistence, sensitively depends on the model geometry. The temperature at which the system becomes completely wet is considerably higher than that for a flat wall.
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Affiliation(s)
- Alexandr Malijevský
- E Hála Laboratory of Thermodynamics, Institute of Chemical Process Fundamentals, Academy of Sciences, 16502 Prague 6, Czech Republic. Department of Physical Chemistry, Institute of Chemical Technology, Prague, 166 28 Praha 6, Czech Republic
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15
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Nguyen PT, Do D, Nicholson D. Pore connectivity and hysteresis in gas adsorption: A simple three-pore model. Colloids Surf A Physicochem Eng Asp 2013. [DOI: 10.1016/j.colsurfa.2013.03.028] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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16
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Nguyen PTM, Do DD, Nicholson D. On the irreversibility of the adsorption isotherm in a closed-end pore. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:2927-2934. [PMID: 23398281 DOI: 10.1021/la304876m] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We present a simulation study of argon adsorption in a closed-end mesopore of uniform diameter in order to investigate the occurrence of hysteresis and propose two principal reasons for its existence: the variation in the shape and radius of curvature of the meniscus and the change in the packing of adsorbate during adsorption and desorption. This interpretation differs from classical theories that neglect both of these factors, and therefore find that adsorption-desorption in a closed-end pore is reversible. A detailed simulation study of the effects of temperature on the microscopic behavior of the adsorbate supports the interpretation proposed here.
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Affiliation(s)
- Phuong T M Nguyen
- School of Chemical Engineering, University of Queensland, St. Lucia, QLD 4072, Australia
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17
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Berlier G, Gastaldi L, Ugazio E, Miletto I, Iliade P, Sapino S. Stabilization of quercetin flavonoid in MCM-41 mesoporous silica: positive effect of surface functionalization. J Colloid Interface Sci 2013; 393:109-18. [DOI: 10.1016/j.jcis.2012.10.073] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 10/29/2012] [Accepted: 10/30/2012] [Indexed: 01/04/2023]
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18
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Coasne B, Galarneau A, Pellenq RJM, Di Renzo F. Adsorption, intrusion and freezing in porous silica: the view from the nanoscale. Chem Soc Rev 2013; 42:4141-71. [PMID: 23348418 DOI: 10.1039/c2cs35384a] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Benoit Coasne
- Institut Charles Gerhardt Montpellier, CNRS (UMR 5253), University Montpellier 2, ENSCM, 8 rue de l'Ecole Normale, 34296 Montpellier, France.
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19
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Malijevský A. Does adsorption in a single nanogroove exhibit hysteresis? J Chem Phys 2012; 137:214704. [DOI: 10.1063/1.4769257] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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20
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Liu Z, Do DD, Nicholson D. A thermodynamic study of the mid-density scheme to determine the equilibrium phase transition in cylindrical pores. MOLECULAR SIMULATION 2012. [DOI: 10.1080/08927022.2011.613383] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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21
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Ancilotto F, Da Re M, Grubišić S, Hernando A, Silvestrelli P, Toigo F. Grand Canonical Monte Carlo study of argon adsorption in aluminium nanopores. Mol Phys 2011. [DOI: 10.1080/00268976.2011.610369] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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22
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Horikawa T, Do DD, Nicholson D. Capillary condensation of adsorbates in porous materials. Adv Colloid Interface Sci 2011; 169:40-58. [PMID: 21937014 DOI: 10.1016/j.cis.2011.08.003] [Citation(s) in RCA: 161] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 08/26/2011] [Accepted: 08/27/2011] [Indexed: 11/30/2022]
Abstract
Hysteresis in capillary condensation is important for the fundamental study and application of porous materials, and yet experiments on porous materials are sometimes difficult to interpret because of the many interactions and complex solid structures involved in the condensation and evaporation processes. Here we make an overview of the significant progress in understanding capillary condensation and hysteresis phenomena in mesopores that have followed from experiment and simulation applied to highly ordered mesoporous materials such as MCM-41 and SBA-15 over the last few decades.
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Affiliation(s)
- Toshihide Horikawa
- School of Chemical Engineering, University of Queensland, St. Lucia, Qld 4072, Australia
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23
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Wang Y, Do D, Nicholson D. Study of heat of adsorption across the capillary condensation in cylindrical pores. Colloids Surf A Physicochem Eng Asp 2011. [DOI: 10.1016/j.colsurfa.2011.02.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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24
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Fan C, Do DD, Nicholson D. On the cavitation and pore blocking in slit-shaped ink-bottle pores. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:3511-3526. [PMID: 21370903 DOI: 10.1021/la104279v] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We present GCMC simulations of argon adsorption in slit pores of different channel geometry. We show that the isotherm for an ink-bottle pore can be reconstructed as a linear combination of the local isotherms of appropriately chosen independent unit cells. Second, depending on the system parameters and operating conditions, the phenomena of cavitation and pore blocking can occur for a given configuration of the ink-bottle pore by varying the geometrical aspect ratio. Although it has been argued in the literature that the geometrical aspects of the system govern the evaporation mechanism (either cavitation or pore blocking), we here put forward an argument that the local compressibility in different parts of the ink-bottle pore is the deciding factor for evaporation. When the fluid in the small neck is strongly bound, cavitation is the governing process, and molecules in the cavity evaporate to the surrounding bulk gas via a mass transfer mechanism through the pore neck. When the pore neck is sufficiently large, the system of neck and cavity evaporates at the same pressure, which is a consequence of the comparable compressibility between the fluid in the neck and that in the cavity. This suggests that local compressibility is the measure of cohesiveness of the fluid prior to evaporation. One consequence that we derive from the analysis of isotherms of a number of connected pores is that by analyzing the adsorption branch or the desorption branch of an experimental isotherm may not lead to the correct pore sizes and the correct pore volume distribution.
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Affiliation(s)
- Chunyan Fan
- School of Chemical Engineering, University of Queensland, St. Lucia, Qld 4072 Australia
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25
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Coasne B, Alba-Simionesco C, Audonnet F, Dosseh G, Gubbins KE. Adsorption, structure and dynamics of benzene in ordered and disordered porous carbons. Phys Chem Chem Phys 2011; 13:3748-57. [DOI: 10.1039/c0cp02205e] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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26
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Bonnaud PA, Coasne B, Pellenq RJM. Molecular simulation of water confined in nanoporous silica. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:284110. [PMID: 21399282 DOI: 10.1088/0953-8984/22/28/284110] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
This paper reports on a molecular simulation study of the thermodynamics, structure and dynamics of water confined at ambient temperature in hydroxylated silica nanopores of a width H = 10 and 20 Å. The adsorption isotherms for water in these nanopores resemble those observed for experimental samples; the adsorbed amount increases continuously in the multilayer adsorption regime until a jump occurs due to capillary condensation of the fluid within the pore. Strong layering of water in the vicinity of the silica surfaces is observed as marked density oscillations are observed up to 8 Å from the surface in the density profiles for confined water. Our results indicate that water molecules within the first adsorbed layer tend to adopt a H-down orientation with respect to the silica substrate. For all pore sizes and adsorbed amounts, the self-diffusivity of confined water is lower than the bulk, due to the hydrophilic interaction between the water molecules and the hydroxylated silica surface. Our results also suggest that the self-diffusivity of confined water is sensitive to the adsorbed amount.
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Affiliation(s)
- P A Bonnaud
- Centre Interdisciplinaire des Nanosciences de Marseille, CNRS and Aix-Marseille Université, Campus de Luminy, F-13288 Marseille Cedex 9, France
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27
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Bruschi L, Mistura G, Liu L, Lee W, Gösele U, Coasne B. Capillary condensation and evaporation in alumina nanopores with controlled modulations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:11894-11898. [PMID: 20491494 DOI: 10.1021/la1011082] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Capillary condensation in nanoporous anodic aluminum oxide presenting not interconnected pores with controlled modulations is studied using adsorption experiments and molecular simulations. Both the experimental and simulation data show that capillary condensation and evaporation are driven by the smallest size of the nanopore (constriction). The adsorption isotherms for the open and closed pores are almost identical if constrictions are added to the system. The latter result implies that the type of pore ending does not matter in modulated pores. Thus, the presence of hysteresis loops observed in adsorption isotherms measured in straight nanopores with closed bottom ends can be explained in terms of geometrical inhomogeneities along the pore axis. More generally, these results provide a general picture of capillary condensation and evaporation in constricted or modulated pores that can be used for the interpretation of adsorption in disordered porous materials.
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Affiliation(s)
- Lorenzo Bruschi
- Dipartimento di Fisica G.Galilei and CNISM, Università di Padova, via Marzolo 8, 35131 Padova, Italy
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Coasne B, Galarneau A, Di Renzo F, Pellenq RJM. Molecular simulation of nitrogen adsorption in nanoporous silica. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:10872-10881. [PMID: 20459091 DOI: 10.1021/la100757b] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
This article reports on a molecular simulation study of nitrogen adsorption and condensation at 77 K in atomistic silica cylindrical nanopores (MCM-41). Two models are considered for the nitrogen molecule and its interaction with the silica substrate. In the "pea" model, the nitrogen molecule is described as a single Lennard-Jones sphere and only Lennard-Jones interactions between the nitrogen molecule and the oxygens atoms of the silica substrate are taken into account. In the "bean" model (TraPPE force field), the nitrogen molecule is composed of two Lennard-Jones sites and a linear array of three charges on the atomic positions and at the center of the nitrogen-nitrogen bond. In the bean model, the interactions between the sites on the nitrogen molecule and the Si, O, and H atoms of the substrate are the sum of the Coulombic and dispersion interactions with a repulsive short-range contribution. The data obtained with the pea and bean models in silica nanopores conform to the typical behavior observed in the experiments for adsorption/condensation in cylindrical MCM-41 nanopores; the adsorbed amount increases continuously in the multilayer adsorption regime until an irreversible jump occurs because of capillary condensation and evaporation of the fluid within the pore. Our results suggest that the pea model can be used for characterization purposes where one is interested in capturing the global experimental behavior upon adsorption and desorption in silica nanopores. However, the bean model is more suitable to investigating the details of the interaction with the surface because this model, which accounts for the partial charges located on the nitrogen atoms of the molecule (quadrupole), allows a description of the specific interactions between this adsorbate and silica surfaces (silanol groups and siloxane bridges) or grafted silica surfaces. In particular, the bean model provides a more realistic picture of nitrogen adsorption in the vicinity of silica surfaces or confined in silica nanopores, where the isosteric heat of adsorption curves show that the nitrogen molecule in this model is sensitive to the surface heterogeneity.
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Affiliation(s)
- B Coasne
- Institut Charles Gerhardt Montpellier, UMR 5253 CNRS/UM2/ENSCM/UM1, ENSCM, 8 rue de l'Ecole Normale, 34296 Montpellier Cedex 05, France.
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29
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Coasne B, Alba-Simionesco C, Audonnet F, Dosseh G, Gubbins KE. Adsorption and structure of benzene on silica surfaces and in nanopores. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:10648-10659. [PMID: 19670890 DOI: 10.1021/la900984z] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Grand canonical Monte Carlo simulations are used to study the adsorption of benzene on atomistic silica surfaces and in cylindrical nanopores. The effect of temperature and surface chemistry is addressed by studying the adsorption of benzene at 293 and 323 K on both fully and partially hydroxylated silica surfaces or nanopores. We also consider the adsorption of benzene in a cylindrical nanopore of diameter D=3.6 nm and compare our results with those obtained for planar surfaces. The structure of benzene in the vicinity of the planar surface and confined in the cylindrical nanopore is determined by calculating orientational order parameters and examining positional pair correlation functions. The density profiles of adsorbed benzene reveal the strong layering of the adsorbate, which decays with the distance from the silica surface. At a given temperature and at low pressures, the film adsorbed at the fully hydroxylated silica surface is larger than that for the partially hydroxylated silica surface. This result is due to an increase in the density of silanol groups that induces an increase in the polarity of the silica surface, which becomes more attractive for the adsorbate. Our results also suggest that the benzene molecules prefer an orientation in which their ring is nearly perpendicular to the surface when fully hydroxylated surfaces are considered. When partially hydroxylated surfaces are considered, a second preferential orientation is observed where the benzene ring forms an angle of approximately 50 degrees with the silica surface. In this case, the average orientation of the benzene molecules appears disordered as in the bulk phase. These results suggest that determining the experimental orientation of benzene in the vicinity of a silica surface is a difficult task even when the surface chemistry is known. Capillary condensation in the nanopores involves a transition from a partially filled pore (a thin film adsorbed at the pore surface) to a completely filled pore configuration where the confined liquid coexists at equilibrium with the external gas phase. The disordered orientation of the adsorbed benzene molecules in the case of the partially hydroxylated surface favors the condensation of benzene molecules (the condensation pressure for this substrate is lower than that for the fully hydroxylated surface). Finally, these results are consistent with the structural analysis, showing that (1) benzene tends to relax its liquid structure a little in order to optimize its molecular arrangement near the pore wall and (2) the disordering of the liquid structure induced by the surface becomes stronger as the interaction with the pore wall increases.
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Affiliation(s)
- Benoit Coasne
- Institut Charles Gerhardt Montpellier, UMR 5253 CNRS, Université Montpellier 2, ENSCM, Place Eugene Bataillon, 34095 Montpellier Cedex 05, France.
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30
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Naumov S, Valiullin R, Kärger J, Monson PA. Understanding adsorption and desorption processes in mesoporous materials with independent disordered channels. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:031607. [PMID: 19905123 DOI: 10.1103/physreve.80.031607] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2009] [Indexed: 05/28/2023]
Abstract
Using a lattice-gas model in mean-field theory, we discuss the problem of how adsorption and desorption of fluids in independent cylinderlike pores is influenced by variations in the pore diameter along the length of the pore, surface roughness of the pore walls, and chemical heterogeneity. We also consider the impact of contact with the bulk phase via the pore opening and the possibility of interactions between neighboring pores via a liquid film on the external surface of the material. We find that a combination of pore size variation along the length of the pore and surface roughness yields sorption hysteresis similar to that found in systems with three-dimensional disordered pore networks such as porous glasses. Our results are especially relevant to adsorption and desorption in porous silicon materials with independent linear pores and apparently anomalous features of the behavior in these systems can be accounted for within the context of the present model.
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Affiliation(s)
- Sergej Naumov
- Fakultät für Physik und Geowissenschaften, Univerität Leipzig, D-04103 Leipzig, Germany
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31
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Pellenq RJM, Coasne B, Denoyel RO, Coussy O. Simple phenomenological model for phase transitions in confined geometry. 2. Capillary condensation/evaporation in cylindrical mesopores. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:1393-1402. [PMID: 19138076 DOI: 10.1021/la8020244] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A simple phenomenological model that describes capillary condensation and evaporation of pure fluids confined in cylindrical mesopores is presented. Following the work of Celestini (Celestini, F. Phys. Lett. A 1997, 228, 84), the free energy density of the system is derived using interfacial tensions and a corrective term that accounts for the interaction coupling between the vapor/adsorbed liquid and the adsorbed liquid/adsorbent interfaces. This corrective term is shown to be consistent with the Gibbs adsorption isotherm and assessed by standard adsorption tests. This model reveals that capillary condensation and evaporation are metastable and equilibrium processes, respectively, hence exhibiting the existence of a hysteresis loop inadsorption/desorption isotherm that is well-known in experiment. We extend the phenomenological model of Celestini to give a quantitative description of adsorption on the pore wall and hysteresis width evolution with temperature and confinement. Direct quantitative comparison is made with experimental data for confined argon. Used as a characterizing tool, this integrated model allows in a single fit of an experimental adsorption/desorption isotherm assessing essential characterization data such as the specific surface area, pore volume, and mean pore size.
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Affiliation(s)
- Roland J-M Pellenq
- Centre Interdisciplinaire des Nanosciences de Marseille, CINaM, UPR CNRS 3118, Campus de Luminy, 13288 Marseille Cedex 09, France.
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32
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Coasne B, Mezy A, Pellenq RJM, Ravot D, Tedenac JC. Zinc Oxide Nanostructures Confined in Porous Silicas. J Am Chem Soc 2009; 131:2185-98. [PMID: 19199634 DOI: 10.1021/ja806666n] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Benoit Coasne
- Institut Charles Gerhardt Montpellier, UMR 5253 CNRS, Université Montpellier 2, ENSCM, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77, Massachusetts Avenue, Cambridge, Massachusetts 02139, and Centre Interdisciplinaire des Nanosciences de Marseille, UPR 3118 CNRS, Campus de Luminy, 13288 Marseilles, France
| | - Aude Mezy
- Institut Charles Gerhardt Montpellier, UMR 5253 CNRS, Université Montpellier 2, ENSCM, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77, Massachusetts Avenue, Cambridge, Massachusetts 02139, and Centre Interdisciplinaire des Nanosciences de Marseille, UPR 3118 CNRS, Campus de Luminy, 13288 Marseilles, France
| | - R. J. M. Pellenq
- Institut Charles Gerhardt Montpellier, UMR 5253 CNRS, Université Montpellier 2, ENSCM, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77, Massachusetts Avenue, Cambridge, Massachusetts 02139, and Centre Interdisciplinaire des Nanosciences de Marseille, UPR 3118 CNRS, Campus de Luminy, 13288 Marseilles, France
| | - D. Ravot
- Institut Charles Gerhardt Montpellier, UMR 5253 CNRS, Université Montpellier 2, ENSCM, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77, Massachusetts Avenue, Cambridge, Massachusetts 02139, and Centre Interdisciplinaire des Nanosciences de Marseille, UPR 3118 CNRS, Campus de Luminy, 13288 Marseilles, France
| | - J. C. Tedenac
- Institut Charles Gerhardt Montpellier, UMR 5253 CNRS, Université Montpellier 2, ENSCM, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77, Massachusetts Avenue, Cambridge, Massachusetts 02139, and Centre Interdisciplinaire des Nanosciences de Marseille, UPR 3118 CNRS, Campus de Luminy, 13288 Marseilles, France
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33
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Gulmen TS, Thompson WH. Grand canonical Monte Carlo simulations of acetonitrile filling of silica pores of varying hydrophilicity/hydrophobicity. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:1103-1111. [PMID: 19113811 DOI: 10.1021/la801896g] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Grand canonical Monte Carlo simulations have been used to determine the equilibrium density of acetonitrile in model amorphous silica pores with varying radius and surface chemistry. Pores of diameter approximately 2-4 nm were considered with different ratios of surface -OH moieties to -OC(CH(3))(3) groups. The calculations found that the acetonitrile density in the interior of all the pores is essentially identical with that of the bulk liquid. On the other hand, a slightly elevated liquid density is observed near the pore surface for pores with only -OH surface moieties. Replacement of surface -OH groups with -OC(CH(3))(3) units lengthens the liquid/pore interfacial region as acetonitrile molecules can insert themselves between the -OC(CH(3))(3) units. The results indicate that the major effect of changing the surface functionality comes from the differences in excluded volume rather than hydrogen-bonding effects. Finally, the choice of the acetonitrile potential can qualitatively change the results.
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Affiliation(s)
- Tolga S Gulmen
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, USA
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34
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Naumov S, Khokhlov A, Valiullin R, Kärger J, Monson PA. Understanding capillary condensation and hysteresis in porous silicon: network effects within independent pores. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 78:060601. [PMID: 19256790 DOI: 10.1103/physreve.78.060601] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Indexed: 05/27/2023]
Abstract
The ability to exert a significant degree of pore structure control in porous silicon materials has made them attractive materials for the experimental investigation of the relationship between pore structure, capillary condensation, and hysteresis phenomena. Using both experimental measurements and a lattice gas model in mean field theory, we have investigated the role of pore size inhomogeneities and surface roughness on capillary condensation of N2 at 77K in porous silicon with linear pores. Our results resolve some puzzling features of earlier experimental work. We find that this material has more in common with disordered materials such as Vycor glass than the idealized smooth-walled cylindrical pores discussed in the classical adsorption literature. We provide strong evidence that this behavior comes from the complexity of the processes within independent linear pores, arising from the pore size inhomogeneities along the pore axis, rather than from cooperative effects between different pores.
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Affiliation(s)
- Sergej Naumov
- Department of Interface Physics, University of Leipzig, D-04103 Leipzig, Germany
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35
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Ustinov EA. The special features of equilibrium adsorption of argon on homogeneous and inhomogeneous surfaces. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2008. [DOI: 10.1134/s0036024408120285] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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36
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Bruschi L, Fois G, Mistura G, Sklarek K, Hillebrand R, Steinhart M, Gösele U. Adsorption hysteresis in self-ordered nanoporous alumina. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:10936-10941. [PMID: 18729482 DOI: 10.1021/la801493b] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We performed systematic adsorption studies using self-ordered nanoporous anodic aluminum oxide (AAO) in an extended range of mean pore diameters and with different pore topologies. These matrices were characterized by straight cylindrical pores having a narrow pore size distribution and no interconnections. Pronounced hysteresis loops between adsorption and desorption cycles were observed even in the case of pores closed at one end. These results are in contrast with macroscopic theoretical models and detailed numerical simulations of the adsorption in a single pore. Extensive measurements involving adsorption isotherms, reversal curves, and subloops carried out in closed-bottom pores suggest that the pores do not desorb independently from one another.
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Affiliation(s)
- Lorenzo Bruschi
- Dipartimento di Fisica G.Galilei, Universita di Padova, via Marzolo 8, 35131 Padova, Italy
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37
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Coasne B, Di Renzo F, Galarneau A, Pellenq RJM. Adsorption of simple fluid on silica surface and nanopore: effect of surface chemistry and pore shape. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:7285-7293. [PMID: 18522440 DOI: 10.1021/la800567g] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
This paper reports a molecular simulation study on the adsorption of simple fluids (argon at 77 K) on hydroxylated silica surfaces and nanopores. The effect of surface chemistry is addressed by considering substrates with either partially or fully hydroxylated surfaces. We also investigate the effect of pore shape on adsorption and capillary condensation by comparing the results for cylindrical and hexagonal nanopores having equivalent sections (i.e., equal section areas). Due to the increase in the polarity of the surface with the density of OH groups, the adsorbed amounts for fully hydroxylated surfaces are found to be larger than those for partially hydroxylated surfaces. Both the adsorption isotherms for the cylindrical and hexagonal pores conform to the typical behavior observed in the experiments for adsorption/condensation in cylindrical nanopores MCM-41. Capillary condensation occurs through an irreversible discontinuous transition between the partially filled and the completely filled configurations, while evaporation occurs through the displacement at equilibrium of a hemispherical meniscus along the pore axis. Our data are also used to discuss the effect of surface chemistry and pore shape on the BET method. The BET surface for fully hydroxylated surfaces is much larger (by 10-20%) than the true geometrical surface. In contrast, the BET surface significantly underestimates the true surface when partially hydroxylated surfaces are considered. These results suggest that the surface chemistry and the choice of the system adsorbate/adsorbent is crucial in determining the surface area of solids using the BET method.
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Affiliation(s)
- Benoit Coasne
- Institut Charles Gerhardt Montpellier, CNRS (UMR 5253) and Université Montpellier 2, Montpellier, France.
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38
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Monson PA. Mean field kinetic theory for a lattice gas model of fluids confined in porous materials. J Chem Phys 2008; 128:084701. [DOI: 10.1063/1.2837287] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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39
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Coasne B, Galarneau A, Di Renzo F, Pellenq RJM. Molecular simulation of adsorption and intrusion in nanopores. ADSORPTION 2008. [DOI: 10.1007/s10450-008-9104-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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40
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41
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Mitropoulos A. The Kelvin equation. J Colloid Interface Sci 2008; 317:643-8. [DOI: 10.1016/j.jcis.2007.10.001] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Revised: 09/28/2007] [Accepted: 10/01/2007] [Indexed: 11/29/2022]
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42
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Morishige K, Ishino M. Lower closure point of adsorption hysteresis in ordered mesoporous silicas. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:11021-6. [PMID: 17894507 DOI: 10.1021/la700904d] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
To examine the nature of the lower closure point of adsorption hysteresis in ordered mesoporous silicas, we measured the temperature dependence of the adsorption-desorption isotherm of nitrogen for three kinds of ordered silicas with cagelike pores and three kinds of ordered silicas with cylindrical pores. The lower closure point pressure of nitrogen in the cagelike pores with sufficiently small necks, that is, the cavitation pressure of a confined liquid, did not depend appreciably on the cage size in the temperature region far away from a hysteresis critical temperature (Tch) but its cage-size dependence was noticeable in the vicinity of Tch. The lower closure point in the cylindrical pores depended on the pore size, and its thermal behavior was totally different from that in the cagelike pores. Nevertheless, the hysteresis critical points of nitrogen in the ordered mesoporous silicas, which are defined as a threshold of temperatures (Tch) and pressure above which reversible capillary condensation takes place in a given size and shape of pores, fell on a common line in a temperature-pressure diagram regardless of the pore geometries. We consider this finding as evidence that capillary evaporation in the cylindrical pores follows a cavitation process in the vicinity of Tch in the same way as that in the cagelike pores and also that the low limit of the hysteresis loop that has been long recognized since 1965 is due to the occurrence of a vapor bubble in a stretched metastable liquid confined to the pores with decreasing pressure (cavitation).
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Affiliation(s)
- Kunimitsu Morishige
- Department of Chemistry, Okayama University of Science, 1-1 Ridai-cho, Okayama 700-0005, Japan
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43
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Puibasset J. Adsorption∕desorption hysteresis of simple fluids confined in realistic heterogeneous silica mesopores of micrometric length: A new analysis exploiting a multiscale Monte Carlo approach. J Chem Phys 2007; 127:154701. [DOI: 10.1063/1.2790423] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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44
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Molecular simulation of the adsorption and structure of benzene confined in mesoporous silicas. ADSORPTION 2007. [DOI: 10.1007/s10450-007-9051-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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45
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Hung FR, Bhattacharya S, Coasne B, Thommes M, Gubbins KE. Argon and krypton adsorption on templated mesoporous silicas: molecular simulation and experiment. ADSORPTION 2007. [DOI: 10.1007/s10450-007-9034-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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46
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Bryk P, Rzysko W, Malijevsky A, Sokołowski S. Capillary condensation in pores with rough walls: A density functional approach. J Colloid Interface Sci 2007; 313:41-52. [PMID: 17531246 DOI: 10.1016/j.jcis.2007.03.077] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2007] [Revised: 03/25/2007] [Accepted: 03/27/2007] [Indexed: 12/01/2022]
Abstract
The effect of surface roughness of slit-like pore walls on the capillary condensation of a spherical particles and short chains is studied. The gas molecules interact with the substrate by a Lennard-Jones (9,3) potential. The rough layer at each pore wall has a variable thickness and density and consists of a disordered quenched matrix of spherical particles. The system is described in the framework of a density functional approach and using computer simulations. The contribution due to attractive van der Waals interactions between adsorbate molecules is described by using first-order mean spherical approximation and mean-field approximation.
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Affiliation(s)
- P Bryk
- Department for the Modeling of Physico-Chemical Processes, Maria Curie-Skłodowska University, 20-031 Lublin, Poland
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47
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Ustinov EA, Fenelonov VB, Yakovlev VA, Eletskii PI. Characterization of the porous structure of carbon materials by means of density functional theory. KINETICS AND CATALYSIS 2007. [DOI: 10.1134/s0023158407040180] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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48
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Husowitz B, Talanquer V. Filling and emptying transitions in cylindrical channels: a density functional approach. J Chem Phys 2007; 126:224703. [PMID: 17581076 DOI: 10.1063/1.2740270] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The authors use density functional theory in a square gradient approximation to investigate capillary condensation and evaporation in cylindrical channels of finite lengths. The model allows them to systematically explore the effect of the pore's length, width, and surface fields on the location of the transition between "empty" (vapor-filled) and "full" (liquid-filled) states. In general, their results indicate that decreasing the length of the channel drastically reduces the range of pore widths where a transition between liquidlike and vaporlike configurations may be observed. For the wide pores, the transition occurs at very low pressures where the liquid is no longer stable, while for the narrow pores, the transition is hindered by the solid-fluid interactions that favor the vapor phase in lyophobic pores. For the limited range of sizes where the transition can occur, the authors' results confirm the existence of two competing minima that may explain the density oscillations observed in a computer simulation of nanochannels. Comparisons between these results with those generated using a phenomenological model based on the capillary approximation indicate that this simplified approach yields fairly good predictions for medium size pores. However, the capillary approach fails to properly describe the properties of the very small and very large pores.
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Affiliation(s)
- B Husowitz
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA
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49
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Rusanov AI, Kuni FM. On the theory of the mechanochemical sorption-striction phenomenon in nanoporous bodies with dispersion forces. RUSS J GEN CHEM+ 2007. [DOI: 10.1134/s1070363207030097] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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50
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Wang XL, Lu ZY, Li ZS, Sun CC. Molecular dynamics simulation study on controlling the adsorption behavior of polyethylene by fine tuning the surface nanodecoration of graphite. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:802-8. [PMID: 17209637 DOI: 10.1021/la061492h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Molecular dynamics simulations are applied to study the adsorption of polyethylene with different chain lengths on patterned graphite surfaces that contain nanoscale protrusions. The influence of the nanostructure on the strong attractive interaction inherently in the hydrophobic polyethylene and hydrophobic graphite system is investigated by modifying the top surface area and the height and the shape of the protrusions. The results are analyzed in terms of the chain configuration, the adsorption energy, the global orientational order parameter, and the normalized surface-chain contacting pair number in the first adsorption layer. When the size of the protrusion increases, the adsorption energy, the order parameter, and the normalized surface-chain contacting pair number decrease at a fixed chain length. When the size of the protrusion is fixed, the average adsorption energy per monomer and the order parameter decrease with increasing chain length because of the stronger intramolecular interactions between the monomers. Changing the protrusion shape in a suitable way will effectively reduce the strong surface-chain interaction.
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Affiliation(s)
- Xiao-Lin Wang
- State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, China
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