Importance of molecular shape in the adsorption of nitrogen, carbon dioxide and methane on surfaces and in confined spaces

Do, D.D.; Junpirom, Supunnee; Nicholson, D.; Do, H.D.

doi:10.1016/j.colsurfa.2009.10.021

Cited by 25 publications

(8 citation statements)

References 29 publications

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“…The adsorption isotherms and the isosteric heats of the two potential models are shown in Figure 2, and we can observe that these differ notably. A similar behavior was found in previous studies for slit pore geometry [16], indicating again that the pseudo-sphere does not properly describe adsorption in small pores. This pore size allows adsorption only at the center of the pore for both the 1-site model and the multi-site potential (Figure 3).…”

Section: Resultssupporting

confidence: 85%

“…The accessible pore volume is defined as the volume accessible to the center of a particle at zero loading. This is determined by the Monte Carlo method of integration as reported in Do et al [16].…”

Section: Grand Canonical Monte Carlo Simulationmentioning

confidence: 99%

“…The importance of the shape of adsorbate on surfaces and in confined spaces has been previously studied considering slit geometry by Do and other researchers [16]. In this study the roles of molecular shape in adsorption of common probes used in the characterization of porous media were analyzed.…”

Section: Introductionmentioning

confidence: 98%

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Effects of potential models on nitrogen adsorption on triangular pore: An improved mixed model for energetic characterization of activated carbon

Mons

Cornette

Toso

et al. 2019

Applied Surface Science

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Section: Resultssupporting

confidence: 85%

Section: Grand Canonical Monte Carlo Simulationmentioning

confidence: 99%

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Effects of potential models on nitrogen adsorption on triangular pore: An improved mixed model for energetic characterization of activated carbon

Mons

Cornette

Toso

et al. 2019

Applied Surface Science

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“…This signifies that the CH 4 molecules both have tripod and inclined configurations toward the pore surfaces. Do et al also found a similar phenomenon for the CH 4 molecules in carbon nanopores, and the molecules are positioned at the angles of 53° and 127° in small pores . The water molecules have no effect on the orientation configurations of the CH 4 molecules in the 0.55 and 1.0 nm pores.…”

Section: Resultsmentioning

confidence: 70%

“…Do et al also found a similar phenomenon for the CH 4 molecules in carbon nanopores, and the molecules are positioned at the angles of 53°and 127°in small pores. 53 The water molecules have no effect on the orientation configurations of the CH 4 molecules in the 0.55 and 1.0 nm pores. However, for the pore size of 2.0 nm, the CH 4 distribution shows that the peaks disappear as a result of the interference of the water molecules; thus, the CH 4 molecules have no preferential orientation in the water-saturated pore.…”

Section: Molecular Configurations Of Dissolved H 2 and Chmentioning

confidence: 95%

Molecular Simulation of H₂ Loss by Dissolution in Caprock Water-Saturated Nanopores under the Nanoconfinement Effect for Underground Hydrogen Storage

Zhang,

Luo,

Yang

et al. 2023

Energy Fuels

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Hydrogen has been regarded as an important clean energy source in recent years. The depleted reservoir has been recognized as an economic geological site for hydrogen storage as a result of its large storage capacity. However, the caprock sealing safety of the reservoir must be considered before underground hydrogen storage. To investigate the hydrogen loss in the caprock, we have studied the H 2 dissolution in the caprock water-saturated kaolinite nanopores using molecular simulations in this work. The H 2 /CH 4 mixture dissolution in the caprock nanopores was also studied to investigate the effect of the CH 4 cushion gas on the H 2 dissolution. The results showed that the H 2 dissolution can increase by up to 27 times the bulk solubility under the impact of nanoconfinement enhancement, and the gas loss through the caprock is mainly by the smaller water-saturated pores. The maximum solubility of H 2 and CH 4 occurs at the 0.55 and 0.6 nm pores, respectively. For the 0.5−0.55 nm pores, the dissolved H 2 density exceeds CH 4 at the H 2 fraction above 50%. As the pore size increases to 2.0 nm, the H 2 and CH 4 solubility is comparable as the nanopore confinement effect gradually becomes weak. However, as the H 2 fraction increases to 80%, the H 2 dissolution dominates over CH 4 , even in the 2.0 nm pore. With the increase of the pore size, the water molecules gradually occupy the strong adsorption sites near the surfaces; thus, the gas molecules start to accumulate in the pore middle. The cushion gas of CH 4 adopts various molecular angles in the pores, which are 50°and 130°in the 0.55 nm pore and tripod and inclined angles of 70°and 110°in the 1.0 nm pore. However, the dissolved H 2 molecules are always perpendicular toward the pore surface, which is not affected by the pore size and water molecules. Under the influence of brine, the solubility of H 2 and CH 4 decreases and the impact of brine is more noticeable in larger pores. The high brine salinity helps to reduce the H 2 loss in the caprock nanopores.

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Kinetic mobility and connectivity in nanopore networks

et al. 2011

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Experimental results for methane and carbon dioxide diffusion in coal, as reported in the literature, often lead to diffusion rates of CO 2 appearing to be much greater than that of CH 4 . The interpretation sometimes offered that the diffusion coefficient for CO 2 is 1-2 orders of magnitude higher than that of CH 4 , violates fundamental principles. Nevertheless, the experimental observations require explanation. In this article, we: (a) Develop simplified models for the fast estimation of transport coefficients. These are compared with comprehensive grand canonical Monte Carlo (GCMC) and molecular dynamic (MD) simulations, collectively defined as molecular simulations (MS), which provide theoretical adsorption isotherms and various transport coefficients based on multicenter potential energy equations. The simplified models are shown to have acceptable accuracies. (b) Use the simplified models to compare diffusivities of CO 2 and CH 4 in carbon nanopores. For all cases examined, the diffusivity of CH 4 is always larger than that of CO 2 . (c) Offer two explanations for the apparently contradictory experimental observations (that CO 2 sometimes appears to diffuse much faster than the CH 4 molecule, even though CH 4 is lighter and has smaller adsorption affinity): (i) CH 4 mobility could be significantly reduced by directional forces resulting from irregular pore geometries; and (ii) if pores contain throats with sizes close to the CH 4 molecular diameter, the energy barrier that the methane molecules must overcome to proceed through is much larger than that required for CO 2 . (d) Demonstrate that both mobility and connectivity issues can be addressed using kinetic theory in association with percolation analysis. Furthermore, this method of understanding pore networks provides a number of important quantitative measures including percolation threshold, size of largest cluster, shortest path and tortuosity. Separating different transport mechanisms, as we propose here, provides improved insights into the complex transport phenomena that occur in carbonaceous porous media. In many cases, diffusivities reported in the literature with mixed mechanisms are better named ''apparent transport coefficients,'' because they lump in other unrelated phenomena, violating the fundamental basis of, or mathematical assumptions imposed on, the definition of diffusion.

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Importance of molecular shape in the adsorption of nitrogen, carbon dioxide and methane on surfaces and in confined spaces

Cited by 25 publications

References 29 publications

Effects of potential models on nitrogen adsorption on triangular pore: An improved mixed model for energetic characterization of activated carbon

Effects of potential models on nitrogen adsorption on triangular pore: An improved mixed model for energetic characterization of activated carbon

Molecular Simulation of H₂ Loss by Dissolution in Caprock Water-Saturated Nanopores under the Nanoconfinement Effect for Underground Hydrogen Storage

Kinetic mobility and connectivity in nanopore networks

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Importance of molecular shape in the adsorption of nitrogen, carbon dioxide and methane on surfaces and in confined spaces

Cited by 25 publications

References 29 publications

Effects of potential models on nitrogen adsorption on triangular pore: An improved mixed model for energetic characterization of activated carbon

Effects of potential models on nitrogen adsorption on triangular pore: An improved mixed model for energetic characterization of activated carbon

Molecular Simulation of H2 Loss by Dissolution in Caprock Water-Saturated Nanopores under the Nanoconfinement Effect for Underground Hydrogen Storage

Kinetic mobility and connectivity in nanopore networks

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Product

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Molecular Simulation of H₂ Loss by Dissolution in Caprock Water-Saturated Nanopores under the Nanoconfinement Effect for Underground Hydrogen Storage