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Yakovlev, V. Yu.; Фомкин, А. А.; Tvardovski, A.V.; Синицын, В. А.; Пулин, А. Л.

doi:10.1023/a:1023498530313

Cited by 22 publications

(17 citation statements)

References 4 publications

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“…Of particular interest is the negative swelling (≈−0.02%) obtained at 300 K for the lowest loading (80 molecules corresponding to 11 mg/g). Volume contraction of porous carbons at low loadings is a well-documented fact in the literature, and the contraction ratio obtained here is typical of those observed experimentally or predicted using thermodynamic models of adsorption-induced deformation . We stress that the present work is, to our knowledge, the first direct observation of such a contraction in a disordered microporous carbon from molecular simulation.…”

Section: Resultssupporting

confidence: 83%

“…A common approximation made in most of the molecular simulation studies is to assume that the kerogen framework is rigid (i.e., kerogen atoms are held frozen during the simulation), allowing one to have a constant volume as required in GCMC calculations and also saving a tremendous amount of computational time as solid–solid interactions (which dominates in number) do not have to be considered. However, it has been known for a very long time that porous carbons, especially coals, can significantly swell, depending on the strength of adsorbate–matrix interactions, under fluid loading. − Some authors have proposed some theoretical frameworks for the prediction of adsorption-induced deformation − that have been applied to coal ,− or kerogen swelling. These methods are all based on the integration of the adsorption isotherm, computed in the undeformed (rigid) matrix with respect to either the free energy or the fluid reservoir pressure .…”

Section: Introductionmentioning

confidence: 99%

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Poroelasticity of Methane-Loaded Mature and Immature Kerogen from Molecular Simulations

Obliger¹,

Valdenaire²,

Capit³

et al. 2018

Langmuir

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While hydrocarbon expulsion from kerogen is certainly the key step in shale oil/gas recovery, the poromechanical couplings governing this desorption process, taking place under a significant pressure gradient, are still poorly understood. Especially, most molecular simulation investigations of hydrocarbon adsorption and transport in kerogen have so far been performed under the rigid matrix approximation, implying that the pore space is independent of pressure, temperature, and fluid loading, or in other words, neglecting poromechanics. Here, using two hydrogenated porous carbon models as proxies for immature and overmature kerogen, that is, highly aliphatic hydrogen-rich vs highly aromatic hydrogen-poor models, we perform an extensive molecular-dynamics-based investigation of the evolution of the poroelastic properties of those matrices with respect to temperature, external pressure, and methane loading as a prototype alkane molecule. The rigid matrix approximation is shown to hold reasonably well for overmature kerogen even though accounting for flexibility has allowed us to observe the well-known small volume contraction at low fluid loading and temperature. Our results demonstrate that immature kerogen is highly deformable. Within the ranges of conditions considered in this work, its density can double and its accessible porosity (to a methane molecule) can increase from 0 to ∼30%. We also show that these deformations are significantly nonaffine (i.e., nonhomogeneous), especially upon fluid adsorption or desorption.

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Section: Resultssupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Poroelasticity of Methane-Loaded Mature and Immature Kerogen from Molecular Simulations

Obliger¹,

Valdenaire²,

Capit³

et al. 2018

Langmuir

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“…It is quite evident that within a temperature range of 216 to 353 K (curves 1-5, see Figure 6) in the course of adsorption, the SiC-AC adsorbent exhibits a non-monotonic deformation, starting from contraction at low adsorption values (for example, η a < 0 for a < 5 mmol/g, curve 1) and turning into expansion as the xenon pressure increases (η a < 0, for a > 5 mmol/g, curve 1). Such a non-monotonic character of the adsorption-induced deformation is inherent to microporous adsorbents, including activated carbons [57][58][59][60][61][62][63][64][65][66][67], zeolites [68], and MOF [69,70]. Neimark and Grenev proposed a theoretical approach [71] based on Polanyi's potential adsorption theory [72], which was later elaborated by Dubinin and coworkers into the theory of volume filling of micropores [14,15].…”

Section: Adsorption-and Temperature-induced Deformation Of the Sic-ac Adsorbentmentioning

confidence: 99%

Peculiarities of Thermodynamic Behaviors of Xenon Adsorption on the Activated Carbon Prepared from Silicon Carbide

et al. 2021

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An activated carbon prepared from silicon carbide by thermochemical synthesis and designated as SiC-AC was studied as an adsorbent for xenon. The examination of textural properties of the SiC-AC adsorbent by nitrogen vapor adsorption measurements at 77 K, powder X-ray diffraction, and scanning electron microscopy revealed a relatively homogeneous microporous structure, a low content of heteroatoms, and an absence of evident transport macropores. The study of xenon adsorption and adsorption-induced deformation of the Si-AC adsorbent over the temperature range of 178 to 393 K and pressures up to 6 MPa disclosed the contraction of the material up to −0.01%, followed by its expansion up to 0.49%. The data on temperature-induced deformation of Si-AC measured within the 260 to 575 K range was approximated by a linear function with a thermal expansion factor of (3 ± 0.15) × 10−6 K−1. These findings of the SiC-AC non-inertness taken together with the non-ideality of an equilibrium xenon gaseous phase allowed us to make accurate calculations of the differential isosteric heats of adsorption, entropy, enthalpy, and heat capacity of the Xe/SiC-AC adsorption system from the experimental adsorption data over the temperature range from 178 to 393 K and pressures up to 6 MPa. The variations in the thermodynamic state functions of the Xe/SiC-AC adsorption system with temperature and amount of adsorbed Xe were attributed to the transitions in the state of the adsorbate in the micropores of SiC-AC from the bound state near the high-energy adsorption sites to the molecular associates.

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“…Measurable volume changes have been reported for a variety of porous materials, such as clays, porous silicas, controlled pore glasses, zeolites, polymers, aerogels, and metal-organic frameworks (MOFs). [1][2][3][4][5][6][7][8][9] In applications such as shale gas extraction, [10][11][12] accounting for these volume changes is important because they can impact the structural integrity and production of a reservoir. In catalysis and separations, changes in adsorbent volume can lead to significant physical degradation of the porous particles comprising the unit operation, adversely affecting its performance.…”

Section: Introductionmentioning

confidence: 99%

Molecular simulation of capillary phase transitions in flexible porous materials

Shen

Siderius

Mahynski

2018

The Journal of Chemical Physics

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We used flat-histogram sampling Monte Carlo to study capillary phase transitions in deformable adsorbent materials. Specifically, we considered a pure adsorbate fluid below its bulk critical temperature within a slit pore of variable pore width. The instantaneous pore width is dictated by a number of factors, such as adsorbate loading, reservoir pressure, fluid-wall interaction, and bare adsorbent properties. In the slit pores studied here, the bare adsorbent free energy was assumed to be biparabolic, consisting of two preferential pore configurations, namely, the narrow pore and the large pore configurations. Four distinct phases could be found in the adsorption isotherms. We found a low-pressure phase transition, driven primarily by capillary condensation/evaporation and accompanied by adsorbent deformation in response. The deformation can be a relatively small contraction/expansion as seen in elastic materials, or a large-scale structural transformation of the adsorbent. We also found a high-pressure transition driven by excluded volume effects, which tends to expand the material and thus results in a large-scale structural transformation of the adsorbent. The adsorption isotherms and osmotic free energies can be rationalized by considering the relative free energy differences between the basins of the bare adsorbent free energy.

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Cited by 22 publications

References 4 publications

Poroelasticity of Methane-Loaded Mature and Immature Kerogen from Molecular Simulations

Poroelasticity of Methane-Loaded Mature and Immature Kerogen from Molecular Simulations

Peculiarities of Thermodynamic Behaviors of Xenon Adsorption on the Activated Carbon Prepared from Silicon Carbide

Molecular simulation of capillary phase transitions in flexible porous materials

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