Natural gas, primarily composed of methane (CH4), offers a greener alternative to conventional fuels. Efficient storage through adsorbed natural gas technology necessitates an understanding of CH4–adsorbent interactions. This study explored CH4 adsorption on activated carbons at 1–35 bar and 298 K, determining an efficiency factor (φ) as an indicator of optimal pore size. In the given system, φ ranged from 2.0 at 1 bar to 2.5 at 35 bar, indicating an increasing trend with pressure. To gain further insights, quantitative contributions (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">${k}_{x}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mi>k</mi> </mrow> <mrow> <mi>x</mi> </mrow> </msub> </math></EquationSource> </InlineEquation>) were established based on different micropore sizes (<InlineEquation ID="IEq2"> <EquationSource Format="TEX">${d}_{{\rm{i}}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mi>d</mi> </mrow> <mrow> <mi mathvariant="normal">i</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> < 0.76 nm, 0.76 nm < <InlineEquation ID="IEq3"> <EquationSource Format="TEX">${d}_{{\rm{ii}}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mi>d</mi> </mrow> <mrow> <mi mathvariant="normal">ii</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> < 1.14 nm, and 1.14 nm < <InlineEquation ID="IEq4"> <EquationSource Format="TEX">${d}_{{\rm{iii}}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mi>d</mi> </mrow> <mrow> <mi mathvariant="normal">iii</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> < 2 nm). At 1 bar, <InlineEquation ID="IEq5"> <EquationSource Format="TEX">${k}_{{\rm{i}}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mi>k</mi> </mrow> <mrow> <mi mathvariant="normal">i</mi> </mrow> </msub> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq6"> <EquationSource Format="TEX">${k}_{{\rm{ii}}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mi>k</mi> </mrow> <mrow> <mi mathvariant="normal">ii</mi> </mrow> </msub> </math></EquationSource> </InlineEquation>, and <InlineEquation ID="IEq7"> <EquationSource Format="TEX">${k}_{{\rm{iii}}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mi>k</mi> </mrow> <mrow> <mi mathvariant="normal">iii</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> contributed 91, 9, and 1%, respectively. These contribution values shifted to 35, 54, and 11% at 35 bar, suggesting that effective pore sizes increase with increasing pressure. Notably, CH4 capacity directly correlated with <InlineEquation ID="IEq8"> <EquationSource Format="TEX">${d}_{{\rm{ii}}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mi>d</mi> </mrow> <mrow> <mi mathvariant="normal">ii</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> in the high-pressure adsorption. Atomistic computations were used to elucidate the role of pore sizes in facilitating CH4 accessibility at different pressures. This comprehensive model provides valuable insights for designing optimal adsorbents, specifically targeting pore size-dependent applications such as gas adsorption and separation, as well as catalyst supports.

Unveiling pore size contributions and host-guest interactions in methane adsorption under varying pressure conditions: a semi-empirical adsorption model

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2025年7月18日

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Jong-Hoon Lee,
Jaewoon Lee,
Duho Kim,
Seul-Yi Lee,
Soo-Jin Park

摘要

Natural gas, primarily composed of methane (CH₄), offers a greener alternative to conventional fuels. Efficient storage through adsorbed natural gas technology necessitates an understanding of CH₄–adsorbent interactions. This study explored CH₄ adsorption on activated carbons at 1–35 bar and 298 K, determining an efficiency factor (φ) as an indicator of optimal pore size. In the given system, φ ranged from 2.0 at 1 bar to 2.5 at 35 bar, indicating an increasing trend with pressure. To gain further insights, quantitative contributions ( ${k}_{x}$ $k_{x}$ ) were established based on different micropore sizes ( ${d}_{{\rm{i}}}$ $d_{i}$ < 0.76 nm, 0.76 nm < ${d}_{{\rm{ii}}}$ $d_{ii}$ < 1.14 nm, and 1.14 nm < ${d}_{{\rm{iii}}}$ $d_{iii}$ < 2 nm). At 1 bar, ${k}_{{\rm{i}}}$ $k_{i}$ , ${k}_{{\rm{ii}}}$ $k_{ii}$ , and ${k}_{{\rm{iii}}}$ $k_{iii}$ contributed 91, 9, and 1%, respectively. These contribution values shifted to 35, 54, and 11% at 35 bar, suggesting that effective pore sizes increase with increasing pressure. Notably, CH₄ capacity directly correlated with ${d}_{{\rm{ii}}}$ $d_{ii}$ in the high-pressure adsorption. Atomistic computations were used to elucidate the role of pore sizes in facilitating CH₄ accessibility at different pressures. This comprehensive model provides valuable insights for designing optimal adsorbents, specifically targeting pore size-dependent applications such as gas adsorption and separation, as well as catalyst supports.