Control mechanism of small organic molecules on methane adsorption capacity of coal

Peng, Xianqi; Ji, Hongmei

doi:10.1016/j.fuel.2022.125904

Cited by 22 publications

(8 citation statements)

References 38 publications

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“…As coalification and mechanical compaction intensify, hydrophilic oxygenous groups within the coal dissociate, and the amount of micropores and the SSA reduce, resulting in a decline in the capacity of the coal for adsorbing CH 4 . When the grade of metamorphism further deepens, the molecular regularity, the degree of aromatic ring condensation, and the SSA all increase, making coals’ limit adsorption capacity to CH 4 increase. , Furthermore, the change rules between the maximum adsorption capacity and the SSA of samples to the coal rank are the same, which implies that the adsorption capacity of samples is determined by the SSA, and the contribution of micropores to the SSA is the highest …”

Section: Results and Discussionmentioning

confidence: 99%

“…When the grade of metamorphism further deepens, the molecular regularity, the degree of aromatic ring condensation, and the SSA all increase, making coals' limit adsorption capacity to CH 4 increase. 49,50 Furthermore, the change rules between the maximum adsorption capacity and the SSA of samples to the coal rank are the same, which implies that the adsorption capacity of samples is determined by the SSA, 51 and the contribution of micropores to the SSA is the highest. 52 Taking L1 (R o,m = 0.5%), M1 (R o,m = 1.18%), M3 (R o,m = 1.74%), and H4 (R o,m = 2.3%) as examples, the V of samples at each temperature shows an escalation upon increasing pressure until reaching V L (Figure 8).…”

Section: Ch 4 Isotherm Adsorption/desorption Characteristicsmentioning

confidence: 94%

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Thermodynamic Characteristics of Methane Adsorption and Desorption on Varied Rank Coals: A Systematic Study

Qiu,

Cai,

Zhou

et al. 2023

Energy Fuels

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Coalbed methane (CBM) primarily exists in the adsorbed state within coalbeds. Understanding adsorption/desorption of coal to CH 4 is highly important for estimating CBM reserves, predicting productivity, and enhancing CBM extraction. In this work, the properties of coal, with R o,m = 0.50−2.54%, adsorbing/desorbing CH 4 , were quantitatively evaluated. Moreover, the variation characteristics were analyzed utilizing the theories of isosteric heat of adsorption, adsorption potential, and surface free energy. The results show that the D−A and Weibull functions have better fitting accuracy, indicating that there is multilayer adsorption or micropore filling; while considering the physical significance of the formula parameters, the Langmuir and desorption equations are more practical, and as the R o,m increases, the V L of samples to CH 4 presents a "U-shape" change. The isosteric heat of adsorption is proportional to the adsorption amount, but the change rates vary due to the different coverage of CH 4 , showing that the low-and medium-metamorphic-degree coals change faster. The adsorption potential exhibits a negative correlation with the adsorption volume, and the adsorption potential of high-metamorphic coal is higher, owing to the higher proportion of micropores. As the adsorption progresses, the cumulative decrease in surface free energy of samples rises, but the rate of change gradually decreases. The adsorption heat and potential of the desorption are higher than those of the adsorption process, and the variation of surface free energy is lower; also, the differences become greater with more CH 4 desorption, revealing the mechanism of the adsorption hysteresis.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Ch 4 Isotherm Adsorption/desorption Characteristicsmentioning

confidence: 94%

Thermodynamic Characteristics of Methane Adsorption and Desorption on Varied Rank Coals: A Systematic Study

Qiu,

Cai,

Zhou

et al. 2023

Energy Fuels

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“…According to the research of Tanaka, η 1 = 0.3878, η 2 = 1.035, η 3 = 0.4249, and η 4 = 1; thus, the d of the hard sphere is 0.37 nm and the volume V is 2.67 × 10 –2 nm 3 . It is worth noting that the diameter of the hard sphere is not the distance between the hydrogen atoms on the methane molecule but can be understood as the size of the electrostatic potential on the methane molecule, − as shown in Figure .…”

Section: Model Constructionmentioning

confidence: 99%

Modeling Methane Adsorption Distance Using Carbon Nanotubes and Bituminous Coal Pore Models

Zha,

Lin,

Liu

et al. 2024

Energy Fuels

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To simplify the analysis of the adsorption of methane by coal, single-walled carbon nanotubes (SWCNTs), slit graphene lamellae, and bituminous coal pore models were constructed, and the adsorption of methane molecules in the three models was studied using molecular dynamics and density functional theory. The results show that methane molecules cannot be adsorbed within carbon nanotubes with a pore size of 0.5 nm. In carbon nanotubes with a pore size of 1 nm, adsorbed methane is influenced by the inner wall of the SWCNTs to induce dipoles and to interact with nearby methane molecules. In large-pore-size carbon nanotubes and graphene sheets, methane molecules adsorb and accumulate on the wall surface to form adsorption rings, the thickness of which gradually increases with the pore size under the effect of curvature, ranging from 0.455 to 0.521 nm. This criterion for adsorption was applied to the pore model of bituminous coal, and 52 adsorbed methane states were determined. Furthermore, the Brunauer–Emmett–Teller equation was used to fit the methane isothermal adsorption curve of the bituminous coal pore model, and the adsorption quantity of methane in a single molecular layer was 54, confirming that the adsorption criterion of 0.521 nm is reasonable.

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“…Furthermore, the conceptual models of bituminous coal and anthracite were constructed using the Amorphous Cell module and the modified basic structural units. Finally, micropores in the two coals were visualized using the Connolly surface [55][56][57].…”

Section: Molecular Structure Simulationmentioning

confidence: 99%

Targeted Stimulation of Micropores by CS2 Extraction on Molecular of Coal

Zhang,

Liu,

Wang

et al. 2024

Molecules

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The targeted stimulation of micropores based on the transformation of coal’s molecular structure is proposed due to the chemical properties and difficult-to-transform properties of micropores. Carbon disulfide (CS2) extraction is used as a targeted stimulation to reveal the internal evolution mechanism of micropore transformation. The variations of microcrystalline structures and micropores of bituminous coal and anthracite extracted by CS2 were analyzed with X-ray diffraction (XRD), low-temperature carbon dioxide (CO2) adsorption, and molecular simulation. The results show that CS2 extraction, with the broken chain effect, swelling effect, and aromatic ring rearrangement effect, can promote micropore generation of bituminous coal by transforming the microcrystalline structure. Furthermore, CS2 extraction on bituminous coal can decrease the average micropore size and increase the micropore volume and area. The aromatic layer fragmentation effect of CS2 extraction on anthracite, compared to the micropore generation effect of the broken chain effect and swelling effect, can enlarge micropores more remarkably, as it induces an enhancement in the average micropore size and a decline in the micropore volume and area. The research is expected to provide a theoretical basis for establishing reservoir stimulation technology based on CS2 extraction.

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Control mechanism of small organic molecules on methane adsorption capacity of coal

Cited by 22 publications

References 38 publications

Thermodynamic Characteristics of Methane Adsorption and Desorption on Varied Rank Coals: A Systematic Study

Thermodynamic Characteristics of Methane Adsorption and Desorption on Varied Rank Coals: A Systematic Study

Modeling Methane Adsorption Distance Using Carbon Nanotubes and Bituminous Coal Pore Models

Targeted Stimulation of Micropores by CS2 Extraction on Molecular of Coal

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