Molecular Level Investigation of CH4 and CO2 Adsorption in Hydrated Calcium-Montmorillonite

Mal Soon Lee; B. Peter McGrail; Roger Rousseau; Vassiliki Alexandra Glezakou

doi:10.1021/acs.jpcc.7b05364

Molecular Level Investigation of CH₄ and CO₂ Adsorption in Hydrated Calcium-Montmorillonite

Mal Soon Lee, B. Peter McGrail, Roger Rousseau, Vassiliki Alexandra Glezakou

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28 Scopus citations

Abstract

We have studied the mechanism of intercalation and methane adsorption from a H₂O/CH₄/CO₂ mixture on a prototypical swelling shale component, Ca-montmorillonite. We employed ab initio molecular dynamics simulations at 323 K and 90 bar to obtain molecular level information on adsorption energetics, speciation, and structural and thermodynamic properties. Interaction of CH₄ with surface Lewis acidic sites (Ca²⁺, surface OH) results in large induced dipoles (∼1 D) that lead to relatively strong adsorption energies compared to interactions of the normally apolar CH₄ that level off once a CH₄ layer is formed. Intercalated CH₄, also exhibits large induced dipoles at lower hydration levels, when the interaction with Ca²⁺ cations are less hindered. CO₂ displaces CH₄ in the coordination sphere of the cations (in the interlayer) or on the surface, thereby driving CH₄ extraction. Our simulations indicate that there is an optimal pressure range (∼70-90 bar) where scCO₂-facilitated CH₄ extraction will be maximized.

Original language	English
Pages (from-to)	1125-1134
Number of pages	10
Journal	Journal of Physical Chemistry C
Volume	122
Issue number	2
DOIs	https://doi.org/10.1021/acs.jpcc.7b05364
State	Published - Jan 18 2018
Externally published	Yes

Funding

This work was supported by the US Department of Energy, Office of Fossil Energy (M.-S.L., B.P.M. and V.-A.G.) and the Office of Basic Energy Science, Division of Chemical Sciences, Geosciences and Biosciences (R.R.), and performed at the Pacific Northwest National Laboratory (PNNL). PNNL is a multiprogram national laboratory operated for DOE by Battelle. Computational resources were provided by PNNL’s Platform for Institutional Computing (PIC) and the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory.

Funders	Funder number
Division of Chemical Sciences, Geosciences and Biosciences	PNNL
Office of Basic Energy Science
US Department of Energy
Office of Fossil Energy

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title = "Molecular Level Investigation of CH4 and CO2 Adsorption in Hydrated Calcium-Montmorillonite",

abstract = "We have studied the mechanism of intercalation and methane adsorption from a H2O/CH4/CO2 mixture on a prototypical swelling shale component, Ca-montmorillonite. We employed ab initio molecular dynamics simulations at 323 K and 90 bar to obtain molecular level information on adsorption energetics, speciation, and structural and thermodynamic properties. Interaction of CH4 with surface Lewis acidic sites (Ca2+, surface OH) results in large induced dipoles (∼1 D) that lead to relatively strong adsorption energies compared to interactions of the normally apolar CH4 that level off once a CH4 layer is formed. Intercalated CH4, also exhibits large induced dipoles at lower hydration levels, when the interaction with Ca2+ cations are less hindered. CO2 displaces CH4 in the coordination sphere of the cations (in the interlayer) or on the surface, thereby driving CH4 extraction. Our simulations indicate that there is an optimal pressure range (∼70-90 bar) where scCO2-facilitated CH4 extraction will be maximized.",

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N2 - We have studied the mechanism of intercalation and methane adsorption from a H2O/CH4/CO2 mixture on a prototypical swelling shale component, Ca-montmorillonite. We employed ab initio molecular dynamics simulations at 323 K and 90 bar to obtain molecular level information on adsorption energetics, speciation, and structural and thermodynamic properties. Interaction of CH4 with surface Lewis acidic sites (Ca2+, surface OH) results in large induced dipoles (∼1 D) that lead to relatively strong adsorption energies compared to interactions of the normally apolar CH4 that level off once a CH4 layer is formed. Intercalated CH4, also exhibits large induced dipoles at lower hydration levels, when the interaction with Ca2+ cations are less hindered. CO2 displaces CH4 in the coordination sphere of the cations (in the interlayer) or on the surface, thereby driving CH4 extraction. Our simulations indicate that there is an optimal pressure range (∼70-90 bar) where scCO2-facilitated CH4 extraction will be maximized.

AB - We have studied the mechanism of intercalation and methane adsorption from a H2O/CH4/CO2 mixture on a prototypical swelling shale component, Ca-montmorillonite. We employed ab initio molecular dynamics simulations at 323 K and 90 bar to obtain molecular level information on adsorption energetics, speciation, and structural and thermodynamic properties. Interaction of CH4 with surface Lewis acidic sites (Ca2+, surface OH) results in large induced dipoles (∼1 D) that lead to relatively strong adsorption energies compared to interactions of the normally apolar CH4 that level off once a CH4 layer is formed. Intercalated CH4, also exhibits large induced dipoles at lower hydration levels, when the interaction with Ca2+ cations are less hindered. CO2 displaces CH4 in the coordination sphere of the cations (in the interlayer) or on the surface, thereby driving CH4 extraction. Our simulations indicate that there is an optimal pressure range (∼70-90 bar) where scCO2-facilitated CH4 extraction will be maximized.

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Molecular Level Investigation of CH₄ and CO₂ Adsorption in Hydrated Calcium-Montmorillonite

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