Molecular Exchange of CH4and CO2in Coal: Enhanced Coalbed Methane on a Nanoscale†

Tambach, Tim J.; Mathews, Jonathan P.; Bergen, F. van

doi:10.1021/ef900274q

Cited by 47 publications

(22 citation statements)

References 33 publications

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“…) and, hence, better account for the chemical composition of real samples (Billemont et al 2013). We note that other molecular models of coal, which take into account chemical heterogeneities, have been reported in the literature (Tambach et al 2009;Tenney and Lastoskie 2006). Molecular models of coals have been recently reviewed (Mathews et al 2011;Mathews and Chaffee 2012).…”

Section: Introductionmentioning

confidence: 94%

Adsorption of carbon dioxide-methane mixtures in porous carbons: effect of surface chemistry

2013

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A combined experimental and molecular simulation study of the coadsorption of CO 2 and CH 4 in porous carbons is reported. We address the effect of surface chemistry by considering a numerical model of disordered porous carbons which has been modified to include heterochemistry (with a chemical composition consistent with that of the experimental sample). We discuss how realistic the numerical sample is by comparing its pore size distribution, specific surface area, porous volume, and porosity with those for the experimental sample. We also discuss the different criteria used to estimate the latter properties from a geometrical analysis. We demonstrate the ability of the MP method to estimate pore size distribution of porous carbons from nitrogen adsorption isotherms. Both the experimental and simulated coadsorption isotherms resemble those obtained for pure gases (type I in the IUPAC classification). On the other hand, only the porous carbon including the heterogroups allows simulating quantitatively the selectivity of the experimental adsorbent for different carbon dioxide/methane mixtures. This result shows that taking into account the heterochemistry present in porous carbons is crucial to represent correctly adsorption selectivities in such hydrophobic samples. We also show that the adsorbed solution theory (AST) describes quantitatively the simulated and experimental coadsorption isotherms without any parameter adjustment.

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Section: Introductionmentioning

confidence: 94%

Adsorption of carbon dioxide-methane mixtures in porous carbons: effect of surface chemistry

2013

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“…The system studied consists of coal and pure components of CO 2 , CH 4 , and C 2 H 6 . In this study, we focus on a model representation of a bituminous coal (Spiro and Kosky 1982;Tambach et al 2009). A building block of 191 atoms, C100H82O5N2S2, for an intermediate rank coal is shown in Fig.…”

Section: Simulation Setupmentioning

confidence: 99%

Molecular simulation studies of hydrocarbon and carbon dioxide adsorption on coal

et al. 2015

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Sorption isotherms of hydrocarbon and carbon dioxide (CO 2 ) provide crucial information for designing processes to sequester CO 2 and recover natural gas from unmineable coal beds. Methane (CH 4 ), ethane (C 2 H 6 ), and CO 2 adsorption isotherms on dry coal and the temperature effect on their maximum sorption capacity have been studied by performing combined Monte Carlo (MC) and molecular dynamics (MD) simulations at temperatures of 308 and 370 K (35 and 97°C) and at pressures up to 10 MPa. Simulation results demonstrate that absolute sorption (expressed as a mass basis) divided by bulk gas density has negligible temperature effect on CH 4 , C 2 H 6 , and CO 2 sorption on dry coal when pressure is over 6 MPa. CO 2 is more closely packed due to stronger interaction with coal and the stronger interaction between CO 2 molecules compared, respectively, with the interactions between hydrocarbons and coal and between hydrocarbons. The results of this work suggest that the ''a'' constant (proportional to T c 2 /P c ) in the Peng-Robinson equation of state is an important factor affecting the sorption behavior of hydrocarbons. CO 2 injection pressures of lower than 8 MPa may be desirable for CH 4 recovery and CO 2 sequestration. This study provides a quantitative understanding of the effects of temperature on coal sorption capacity for CH 4 , C 2 H 6 , and CO 2 from a microscopic perspective.

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“…Considering the wide distribution of the strong heterogeneity and the complex pore structure of coal [13], to the best of our knowledge, the pores in coal can be classified as micropores (pore size: d < 2 nm), mesopores (2-50 nm), and macropores (d > 50 nm) [14]. Previous research [15,16] has shown that the micropores in coal account for more than 60% of the total pore volume, and the gases of CO 2 and CH 4 are mainly adsorbed in the coal matrix. Different scholars have been studied gas diffusion in coal, which is based on different models of pores.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulation of Diffusion Behavior of CH4, CO2, and N2 in Mid-Rank Coal Vitrinite

Liu

Wang

2019

Energies

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The diffusion characteristics of CH4, CO2, and N2 in coal are important for the study of CO2-enhanced coalbed methane (CO2-ECBM) recovery, which has become the most potential method for carbon sequestration and natural gas recovery. However, quantitative research on the diffusion characteristics of CH4 and the invasive gases (CO2 and N2) in coal, especially those in micropores, still faces enormous challenges. In this paper, the self-, Maxwell’s, and transport diffusions of CO2, CH4, and N2 in mid-rank coal vitrinite (MRCV) macromolecules were simulated based on the molecular dynamics method. The effects of the gas concentration, temperature, and pressure on the diffusion coefficients were examined via the comparison of various ranks. The results indicated that the diffusion coefficients have the order of D(N2) > D(CO2) > D(CH4) in their saturated adsorption states. However, when MRCV adsorbed the same amounts of CH4, CO2, and N2, the self- and transport diffusion coefficients followed the order of DS(N2) > DS(CO2) > DS(CH4) and Dt(CO2) > Dt(N2) > Dt(CH4), respectively. Independent of the gas species, all these diffusion coefficients decreased with increasing gas concentration and increased with increasing temperature. In the saturated adsorption state, the diffusion activation energies of CH4, CO2, and N2 were ordered as CH4 (27.388 kJ/mol) > CO2 (11.832 kJ/mol) > N2 (10.396 kJ/mol), indicating that the diffusion processes of CO2 and N2 occur more easily than CH4. The increase of temperature was more conducive to the swelling equilibrium of coal. For the pressure dependence, the diffusion coefficients first increased until the peak pressure (3 MPa) and then decreased with increasing pressure. In contrast, the diffusion activation energy first decreased and then increased with increasing pressure, in which the peak pressure was also 3 MPa. The swelling rate changed more obviously in high-pressure conditions.

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Molecular Exchange of CH₄and CO₂in Coal: Enhanced Coalbed Methane on a Nanoscale^†

Cited by 47 publications

References 33 publications

Adsorption of carbon dioxide-methane mixtures in porous carbons: effect of surface chemistry

Adsorption of carbon dioxide-methane mixtures in porous carbons: effect of surface chemistry

Molecular simulation studies of hydrocarbon and carbon dioxide adsorption on coal

Molecular Dynamics Simulation of Diffusion Behavior of CH4, CO2, and N2 in Mid-Rank Coal Vitrinite

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