Study on the reactivity of oxygen-containing functional groups in coal with and without adsorbed water in low-temperature oxidation

Xi, Zhilin; Li, Xue; Ke, Xi

doi:10.1016/j.fuel.2021.121454

Cited by 36 publications

(13 citation statements)

References 29 publications

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“…According to the ΔE of all reactions, the reaction sequences can be inferred, that is, they gradually occur from small to large. According to previous experimental analyses, 35,43,44 when ΔE = 0, the reaction can occur spontaneously. When ΔE < 40 kJ/mol, the reaction can occur at room temperature and pressure (T < 30 °C).…”

Section: Inference Of Chain Reactions Of Coal Spontaneous Combustionmentioning

confidence: 84%

Quantum Chemistry Calculation Study on Chain Reaction Mechanisms and Thermodynamic Characteristics of Coal Spontaneous Combustion at Low Temperatures

Huo

Zhu

et al. 2021

ACS Omega

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The coal spontaneous combustion phenomenon seriously affects the safety production of coal mines. Aiming at the problem of complex coal molecular structure and incomplete reaction sequences at present, the mechanisms and thermodynamic parameters of coal spontaneous combustion chain reactions were explored by combining experimental detections and molecular simulations. First, the active groups on the surface of coal were obtained by Fourier transform infrared spectroscopy (FTIR), mainly including methyl (−CH3), methylene (−CH2), methyne (−CH), phenolic hydroxyl (−ArOH), alcohol hydroxyl (−ROH), carboxyl (−COOH), aldehyde (−CHO), and ether (−O−), and the coal molecular models containing functional groups and radicals were established. According to the charge density, electrostatic potential, and frontier orbital theories, the active sites and active bonds were obtained, and a series of reactions were given. The thermodynamic and structural parameters of each reaction were explored. In the chain initiation reaction stage, O2 chemisorption and the self-reaction of radicals play a leading role. In this stage, heat gradually accumulates and various radicals begin to generate, where the intramolecular hydrogen transfer reaction of a peroxide radical (−C–O–O·) can produce the key hydroxyl radical (−O·). In the chain propagation reaction stage, O2 and −O· continuously consume active sites to accelerate the reaction sequences and increase the temperature of coal, and index gases such as CO and CO2 generate, causing the chain cycle reactions to gradually form. The chain termination reaction stage is the formation of stable compounds such as ethers, esters, and quinones, which can inhibit the development of chain reactions. The results can further explain the reaction mechanism of coal spontaneous combustion and provide references for the development and utilization of chemical inhibitors.

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Section: Inference Of Chain Reactions Of Coal Spontaneous Combustionmentioning

confidence: 84%

Quantum Chemistry Calculation Study on Chain Reaction Mechanisms and Thermodynamic Characteristics of Coal Spontaneous Combustion at Low Temperatures

Huo

Zhu

et al. 2021

ACS Omega

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“…On one hand, the adsorbed H 2 O of coal can affect low-temperature oxidation of the oxygenic functional group, C–O, CO, and −COOH in particular . Generally, the low-temperature oxidation occurs for CO under equilibrium H 2 O conditions due to the fact that the energy barrier is 76.14 kJ/mol, much lower than that of C–O (97.14 kJ/mol) and −COOH (120.77 kJ/mol) . On the other hand, H 2 O mainly adsorbs on C–O and −COOH of the coal matrix via hydrogen bonds, leading to a decrease in their content .…”

Section: Resultsmentioning

confidence: 99%

“…73 Generally, the lowtemperature oxidation occurs for CO under equilibrium H 2 O conditions due to the fact that the energy barrier is 76.14 kJ/mol, much lower than that of C−O (97.14 kJ/mol) and −COOH (120.77 kJ/mol). 77 On the other hand, H 2 O mainly adsorbs on C−O and −COOH of the coal matrix via hydrogen bonds, leading to a decrease in their content. 78 However, during low-temperature oxidation, −H with low bond energy in −CH 3 of coal can be substituted for −OH in H 2 O, thereby leading to increasing C−O.…”

Section: Modelingmentioning

confidence: 99%

Influence of H₂O on Adsorbed CH₄ on Coal Displaced by CO₂ Injection: Implication for CO₂ Sequestration in Coal Seam with Enhanced CH₄ Recovery (CO₂-ECBM)

Liu

Wang

Lun

et al. 2021

Ind. Eng. Chem. Res.

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CO 2 -ECBM is capable of realizing CO 2 sequestration and coalbed methane (CH 4 ) production simultaneously. Practical coal seam contains H 2 O, thus significantly influencing adsorption, desorption, diffusion, and flow capability of CO 2 and CH 4 . Accordingly, the impacts of H 2 O on adsorbed CH 4 on coal displaced by CO 2 were investigated to gain a further understanding on CO 2 -ECBM. The results derived from this study indicate that the occurrence of H 2 O with coal positively relates to oxygenic functional groups and mesopores of coal. Particularly, the oxygenic functional group of the coal matrix acts as a primary adsorption site for H 2 O. The mesopore of coal is the main space for H 2 O occurrence. Furthermore, the impact of H 2 O on CO 2 adsorption on coal depends on dissolution capability and competitive adsorption of H 2 O. With respect to coal with a low H 2 O content, the dissolution of CO 2 in H 2 O is dominant at high CO 2 adsorption equilibrium pressure, thus leading to increasing CO 2 adsorption capability of coal, while the opposite trend is applicable for coal with a high H 2 O content. With regard to the displacement process, injecting CO 2 promotes desorption of adsorbed CH 4 from dry and moist-equilibrated coals. The absolute adsorption amount of CO 2 at the equilibrium state for displacement is lower than that in single-component adsorption for both dry and moisture-equilibrated coals at equilibrium pressures below 3 MPa, whereas the adverse trend exists for a high equilibrium pressure range of 3−4 MPa. Moreover, the elevated CO 2 injection pressure favors both CO 2 adsorption and CH 4 desorption on dry and moisture-equilibrated coals. The presence of H 2 O decreases the CO 2 adsorption amount and CH 4 desorption amount of the coals. Therefore, practical implementation of CO 2 -ECBM should focus on the H 2 O dependence of CO 2 sequestration and CH 4 recovery.

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“…Due to the influence of different mine water samples and inhibitors, the functional groups of coal would be changed in different degrees . In order to study the effect of mine water and chloride on functional groups, an infrared spectrometer (Nicolet 380) was used to determine the content of functional groups in different coal samples. , The coal sample and KBr were mixed and ground at a ratio of 1:100. The mold containing the powder was placed in a tablet press and held at a pressure of 10 MPa for 30 s. The fabricated flakes were placed in a Nicolet iS50 Fourier transform infrared spectrometer, and the scanning wavelength range was 4000–400 cm –1 .…”

Section: Experimental Materials and Methodsmentioning

confidence: 99%

Influence of High Sulfate Mine Water on Spontaneous Combustion of Coal

et al. 2022

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Mine water cannot be discharged until it has been treated, which increases the cost of mining and causes environmental damage. This paper attempted to use sulfate mine water as a flame retardant material for the treatment of coal spontaneous combustion (CSC) in underground mines. The temperature-programed experimental device and gas chromatograph were used to simulate the low-temperature oxidation process of coal. Infrared spectroscopy was used to study the influence and inhibition mechanism of mine water and chloride inhibitor on active functional groups. It was found that although the sulfate mine water inhibited the formation of −OH, it accelerated the cleavage of the aromatic ring. The thermogravimetric experiment was used to analyze the ignition temperature and activation energy of different coal samples. It was found that mine water had an obvious effect on inhibiting CSC in the combustion stage, which could increase the oxidation temperature of coal.

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Study on the reactivity of oxygen-containing functional groups in coal with and without adsorbed water in low-temperature oxidation

Cited by 36 publications

References 29 publications

Quantum Chemistry Calculation Study on Chain Reaction Mechanisms and Thermodynamic Characteristics of Coal Spontaneous Combustion at Low Temperatures

Quantum Chemistry Calculation Study on Chain Reaction Mechanisms and Thermodynamic Characteristics of Coal Spontaneous Combustion at Low Temperatures

Influence of H₂O on Adsorbed CH₄ on Coal Displaced by CO₂ Injection: Implication for CO₂ Sequestration in Coal Seam with Enhanced CH₄ Recovery (CO₂-ECBM)

Influence of High Sulfate Mine Water on Spontaneous Combustion of Coal

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Study on the reactivity of oxygen-containing functional groups in coal with and without adsorbed water in low-temperature oxidation

Cited by 36 publications

References 29 publications

Quantum Chemistry Calculation Study on Chain Reaction Mechanisms and Thermodynamic Characteristics of Coal Spontaneous Combustion at Low Temperatures

Quantum Chemistry Calculation Study on Chain Reaction Mechanisms and Thermodynamic Characteristics of Coal Spontaneous Combustion at Low Temperatures

Influence of H2O on Adsorbed CH4 on Coal Displaced by CO2 Injection: Implication for CO2 Sequestration in Coal Seam with Enhanced CH4 Recovery (CO2-ECBM)

Influence of High Sulfate Mine Water on Spontaneous Combustion of Coal

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Influence of H₂O on Adsorbed CH₄ on Coal Displaced by CO₂ Injection: Implication for CO₂ Sequestration in Coal Seam with Enhanced CH₄ Recovery (CO₂-ECBM)