Insight on microscopic mechanisms of CH4 and CO2 adsorption of coal with different ranks

Sun, Yangying; Wang, Liang; Zheng, Siwen; Liao, Xiaoxue; Zhu, Zusong; Zhao, Yuchen

doi:10.1016/j.fuel.2022.125715

Cited by 35 publications

(20 citation statements)

References 37 publications

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“…From Figures and , it can be seen that the number of both molecules decreases at 298–318 K. Among the coal molecules, CH 4 molecules were distributed in low-density scattering and CO 2 molecules were distributed in high-density aggregation in the pores, which confirmed that coal has a complex pore structure with different sizes, in accordance with the study of Sun . Among them, Figure shows that both CH 4 /CO 2 values peaked at 298 K (0.039 g/0.36 g·cm –3 ).…”

Section: Resultsmentioning

confidence: 99%

“…The enthalpy change Δ H can be expressed as the energy change of the adsorption process as shown in eq , : normalΔ H = − Q st where Q st is the heat of adsorption, kJ/mol.…”

Section: Models and Methodsmentioning

confidence: 99%

“…where P c is the critical pressure, MPa; T c is the critical temperature of adsorbate molecules, K. The enthalpy change ΔH can be expressed as the energy change of the adsorption process as shown in eq 8 45,46 :…”

Section: Adsorption Calculatormentioning

confidence: 99%

“…From Figures 3 and 4, it can be seen that the number of both molecules decreases at 298−318 K. Among the coal molecules, CH 4 molecules were distributed in low-density scattering and CO 2 molecules were distributed in high-density aggregation in the pores, which confirmed that coal has a complex pore structure with different sizes, in accordance with the study of Sun. 46 Among them, Figure 4 shows that both CH 4 /CO 2 values peaked at 298 K (0.039 g/0.36 g•cm −3 ). However, there are positive and negative values of CO 2 mass density with increasing temperature, and due to its dynamic exchange with the outside of the supercell, CO 2 is present at the boundary line of the cell, while CH 4 is not reflected because the CO 2 adsorption capacity is much larger than that of CH 4 .…”

Section: Adsorption Calculatormentioning

confidence: 99%

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Molecular Simulation of Thermodynamic Properties of CH₄/CO₂ Adsorption by Coal Molecules at Different Temperatures and Moisture Contents under Variable Pressure Conditions

Jia,

Wu,

2023

ACS Omega

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In order to further elucidate the thermodynamic mechanism of CH 4 /CO 2 adsorption by coal molecules, the adsorption behavior of a molecular model of coal (C 206 H 128 O 36 N 2 ) at Wucaiwan, Zhundong was investigated by applying Materials Studio 2020 and Monte Carlo (GCMC) simulation methods, and the adsorption behavior of CH 4 and CO 2 was studied from the thermodynamic point of view under the conditions of different temperatures, pressures, and moisture contents. The results showed that at different temperatures or moisture contents, CH 4 molecules had a low-density scattering distribution and CO 2 molecules had a high-density polymerization distribution. Temperature and moisture content and adsorption constants a and b were negatively correlated. Under the same conditions, the relationship between single- and binary-component adsorption amounts was CO 2 > CH 4 and the relationship between heat of adsorption was CO 2 > CH 4 . When adsorption potential energy or entropy of adsorption was the same, the adsorption capacity was CO 2 > CH 4 . Temperatures and moisture contents were negatively correlated with the total adsorption capacity of CH 4 /CO 2 ; pressure was positively correlated with the total adsorption capacity of CH 4 /CO 2 . The effect of temperature on the equivalent heat of adsorption was greater than that of pressure at different temperatures, and the entropy of adsorption was positively correlated between temperature and CH 4 /CO 2 , while the amount of adsorption was negatively correlated with the entropy of adsorption. The effect of moisture content on the equivalent heat of adsorption was greater than that of pressure at different moisture contents, and the entropy of adsorption was negatively correlated between moisture content and amount of adsorption. The adsorption entropy of CH 4 /CO 2 was negatively correlated, and the adsorption amount was positively correlated to the adsorption entropy. At a temperature above 318 K or moisture content above 10%, the total CH 4 /CO 2 adsorption decreased significantly and the CO 2 adsorption decreased significantly. From a thermodynamic point of view, the presence of a large amount of H 2 O had a much greater effect on CO 2 than on CH 4 , and an increase in temperature or moisture content was unfavorable for CO 2 sequestration, CO 2 ...

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Section: Resultsmentioning

confidence: 99%

“…The enthalpy change Δ H can be expressed as the energy change of the adsorption process as shown in eq , : normalΔ H = − Q st where Q st is the heat of adsorption, kJ/mol.…”

Section: Models and Methodsmentioning

confidence: 99%

Section: Adsorption Calculatormentioning

confidence: 99%

Section: Adsorption Calculatormentioning

confidence: 99%

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Molecular Simulation of Thermodynamic Properties of CH₄/CO₂ Adsorption by Coal Molecules at Different Temperatures and Moisture Contents under Variable Pressure Conditions

Jia,

Wu,

2023

ACS Omega

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“…Among them, the adsorption capacity of CH 4 and CO 2 has good linear relationships with the variation of pore volumes obtained from the respective molecular kinetic diameter probes (Figure 13a), and a similar variation pattern was observed between the adsorption capacity and the specific surface area (Figure 13b). Wang et al 27 and Sun et al 46 also suggested that the adsorption of gases in coals with different degrees of metamorphism has a positive correlation with the volume of the micropores. The strain response of coal under compression stress changes the pore structure and reduces the pore volume, specific surface area, and pore connectivity of coal, and a series of changes in pore structure leads to a decrease in adsorption performance.…”

Section: Effect Of Compression Stress On Adsorption Properties 331 Is...mentioning

confidence: 99%

Molecular Simulation of the Pore Structure and Adsorption Properties of Coal under Compression Stress

2023

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The deformation of the macromolecular structure of coal under compression stress may affect the pore structure and adsorption properties. In this study, the Grand Canonical Monte Carlo and molecular dynamics methods were used to investigate the effects of compression stress on the pore structure and adsorption properties of coal, and the coupling relationships between stress, strain, pore structure, and adsorption properties were explored. A macromolecular model of coal was constructed, and uniaxial compression simulation was conducted. The increase of compression stress reduces the pore volume, specific surface area, and connectivity of coal and concentrates the pore size distribution in pores with smaller sizes. The increase of stress leads to a different degree of reduction in the adsorption performance of coal on CH 4 and CO 2 , and the stress sensitivity of CH 4 is slightly stronger than that of CO 2 . The results of adsorption configurations in the pores under different strains indicate that the reduction of adsorption properties is controlled by the pore volume and pore connectivity. The adsorption performance of CH 4 and CO 2 in coal at different strains has a good linear relationship with the volume and specific surface area of the pores; the smaller the volume and specific surface area of the pores, the weaker the adsorption performance of coal. This study clarifies the control of the strain response under compression stress on the pore structure and adsorption properties of coal and provides guidance for the study of adsorption, desorption, and diffusion of CBM.

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In‐situ temperature‐depth profile evaluation of South African unmineable coal seams to determine CO₂ sequestration potential

Premlall,

Kipyegon

2023

Can J Chem Eng

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This study aimed to investigate the sorption behaviour of South African coal seams with relation to the effect of temperature during CO2 sequestration. The excess adsorption isotherms of CO2 adsorption were undertaken using a high‐pressure volumetric system for four coals of different coal rank (denoted by Somkele [SK], anthracite KZN [AN], Tshikondeni [TD], and Syferfontein [SF]). The volumetric pressure step method was conducted at increments of system temperature of 35, 45, 55, and 65°C for pure CO2 adsorption at incremental pressures up to 93 bar. The results showed that high temperatures have a very significant negative effect on the amount of CO2 adsorbed on the coal samples. The high‐rank coal samples (SK and AN) demonstrated elevated CO2 adsorption capacity across all tested temperatures due to their high vitrinite content. The medium‐rank coals (TD and SF) exhibited comparatively lower CO2 adsorption capacity, attributed to the presence of adsorption hindrances such as higher ash content and volatile and mineral matter. The isosteric heat of adsorption revealed an increasing trend with coverage for all coal samples, with higher rank coals displaying greater slopes. The determined range of the isosteric heat of adsorption, spanning from 10 to 59 kJ/mol, indicated that the adsorption process is primarily of a physisorption nature. Three theoretical models (Langmuir, Freundlich, and Temkin) were evaluated and fitted to the sorption experimental data. The Temkin model exhibited superior fitting compared to the Langmuir and Freundlich isotherms. The Temkin isotherm parameters suggest that the adsorption of CO2 onto coal is a physisorption process.

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Insight on microscopic mechanisms of CH4 and CO2 adsorption of coal with different ranks

Cited by 35 publications

References 37 publications

Molecular Simulation of Thermodynamic Properties of CH₄/CO₂ Adsorption by Coal Molecules at Different Temperatures and Moisture Contents under Variable Pressure Conditions

Molecular Simulation of Thermodynamic Properties of CH₄/CO₂ Adsorption by Coal Molecules at Different Temperatures and Moisture Contents under Variable Pressure Conditions

Molecular Simulation of the Pore Structure and Adsorption Properties of Coal under Compression Stress

In‐situ temperature‐depth profile evaluation of South African unmineable coal seams to determine CO₂ sequestration potential

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Insight on microscopic mechanisms of CH4 and CO2 adsorption of coal with different ranks

Cited by 35 publications

References 37 publications

Molecular Simulation of Thermodynamic Properties of CH4/CO2 Adsorption by Coal Molecules at Different Temperatures and Moisture Contents under Variable Pressure Conditions

Molecular Simulation of Thermodynamic Properties of CH4/CO2 Adsorption by Coal Molecules at Different Temperatures and Moisture Contents under Variable Pressure Conditions

Molecular Simulation of the Pore Structure and Adsorption Properties of Coal under Compression Stress

In‐situ temperature‐depth profile evaluation of South African unmineable coal seams to determine CO2 sequestration potential

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Molecular Simulation of Thermodynamic Properties of CH₄/CO₂ Adsorption by Coal Molecules at Different Temperatures and Moisture Contents under Variable Pressure Conditions

Molecular Simulation of Thermodynamic Properties of CH₄/CO₂ Adsorption by Coal Molecules at Different Temperatures and Moisture Contents under Variable Pressure Conditions

In‐situ temperature‐depth profile evaluation of South African unmineable coal seams to determine CO₂ sequestration potential