Effect of acetic acid concentration and dissolution time on the evolution of coal phases: A case report of bituminous coal

Yu, Yanbin; Gao, Chengwei; Yang, Haotian; Cheng, Weimin; Xin, Qilin; Zhang, Xin

doi:10.1016/j.molliq.2021.117298

Cited by 22 publications

(10 citation statements)

References 39 publications

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“…However, due to experimental constraints, the present study focuses solely on analyzing the acidification process at a temperature of 28°C. The dried particles of the coal samples and the standard samples were immersed in the prepared acid solution for 12 hours [ 49 ]. The coal samples were then filtered and dried using a dryer at a temperature of 60°C.…”

Section: Coal Samples and Experimental Methodsmentioning

confidence: 99%

Experimental research on the influence of acid on the chemical and pore structure evolution characteristics of Wenjiaba tectonic coal

Li,

et al. 2024

PLoS ONE

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The chemical and pore structures of coal play a crucial role in determining the content of free gas in coal reservoirs. This study focuses on investigating the impact of acidification transformation on the micro-physical and chemical structure characteristics of coal samples collected from Wenjiaba No. 1 Mine in Guizhou. The research involves a semi-quantitative analysis of the chemical structure parameters and crystal structure of coal samples before and after acidification using Fourier Transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) experiments. Additionally, the evolution characteristics of the pore structure are characterized through high-pressure mercury injection (HP-MIP), low-temperature nitrogen adsorption (LT-N2A), and scanning electron microscopy (SEM). The experimental findings reveal that the acid solution modifies the structural features of coal samples, weakening certain vibrational structures and altering the chemical composition. Specifically, the asymmetric vibration structure of aliphatic CH2, the asymmetric vibration of aliphatic CH3, and the symmetric vibration of CH2 are affected. This leads to a decrease in the contents of -OH and -NH functional groups while increasing aromatic structures. The crystal structure of coal samples primarily dissolves transversely after acidification, affecting intergranular spacing and average height. Acid treatment corrodes mineral particles within coal sample cracks, augmenting porosity, average pore diameter, and the ratio of macro-pores to transitional pores. Moreover, acidification increases fracture width and texture, enhancing the connectivity of the fracture structure in coal samples. These findings provide theoretical insights for optimizing coalbed methane (CBM) extraction and gas control strategies.

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Section: Coal Samples and Experimental Methodsmentioning

confidence: 99%

Experimental research on the influence of acid on the chemical and pore structure evolution characteristics of Wenjiaba tectonic coal

Li,

et al. 2024

PLoS ONE

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“…Existing studies are primarily based on strong acids (e.g., hydrofluoric acid and hydrochloric acid), but in the context of environmental protection, clean energy and the cleanliness of energy have become the key areas of research, and strong acids such as hydrofluoric acid and hydrochloric acid have serious corrosion problems and environmental safety hazards in their use. Yu , shifted the type of acid to acetic acid. This organic weak acid is less harmful to the human body, unregulated, easy to obtain, and environmentally friendly, which has a small degree of ionization and a slower reaction rate.…”

Section: Introductionmentioning

confidence: 99%

“…Based on the practical problem of water injection in low-porosity impermeable coal seams, Yu ,, proposed to study the effect of acetic acid acidification to dissolve the minerals distributed in the pores and fractures of coal, to increase the pore and fracture sizes of the coal, and ultimately to form intertwined through fracture networks to improve the permeability of the coal, improve the amount of water injected into the coal seam, and improve the effect of wetting to achieve the efficacy of strengthening the water injection of coal seams for dust suppression. In this paper, micro-CT was used to conduct scanning tests on bituminous coal samples before and after corrosion with an acetic acid solution of different concentrations, to obtain pore and fracture evolution characteristics before and after corrosion, and to reveal the evolution law of coal microstructure during acetic acid acidification process and its influencing mechanism to provide the experimental basis for acidizing transformation of coal microstructure.…”

Section: Introductionmentioning

confidence: 99%

Porosity and Fracture Changes of Bituminous Coal under Action of Dry–Wet Cycles in Acid Environment

Yu,

Xing,

Cheng

et al. 2024

Energy Fuels

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The application of acetic acid to coal seams can significantly impact the coal's microstructure and properties. In this paper, micro-CT was used to perform CT scanning on two bituminous coal samples before and after 72 h of dissolution with different concentrations of acetic acid solution to quantitatively identify the changes in the components and microstructures of pores, coal matrices, and minerals in the coal with acetic acid concentration. Research has shown that the erosion effect of acetic acid concentration on bituminous coal exhibits a positive correlation, with high concentrations causing more significant open-pore erosion. Additionally, the porosity of coal samples increases with the concentration of acetic acid, and the mineral volume fraction generally decreases. The minerals inside the coal samples are constantly eroded by dissolution and hydrolysis, leading to changes in their state. The interaction of acid corrosion and the dry−wet cycle ultimately causes the deterioration of the physical form of coal and an increase in porosity.

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“…For low-permeability coal seams rich in minerals, acidification technology, which is a type of chemical permeability enhancement, provides a novel strategy for improving the permeability and gas recovery rate of seams. − Zhao et al studied the influence of hydrochloric acid on coal with different metamorphic grades and found a tremendous increase in porosity and permeability after acidification. Xie et al investigated the promoting effects of sodium dodecyl sulfate (SDS) on coal acidification and found that adding SDS to acid solvents can further destroy the initial pore structure of coal and form a complex diversion network.…”

Section: Introductionmentioning

confidence: 99%

Construction of Macromolecular Structural Models of Coal and Simulation of Adsorption under Acidification

He,

Yuan,

et al. 2024

Ind. Eng. Chem. Res.

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We explored the influence of acidification on the structure, wettability, and adsorption capacity of coal based on Xray diffraction, water adsorption tests, elemental analysis, 13 C nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, isothermal adsorption tests, and molecular simulations. The results indicated that the silicate content in the experimental coal samples was high and the optimal acidification condition for improving wettability was 4% hydrofluoric acid with a 6 h reaction time. Under acidification, the aromatic structure in coal changed slightly, while the aliphatic structure and functional groups were significantly altered. In addition, the aliphatic chains were broken to form shorter chains, and the carbon structures changed from methylene and hypomethylene to methyl. Moreover, acidification removed nitrogen atoms and generated a greater number and variety of oxygen-containing groups. The macromolecular structural models of the coal samples and the acidified samples were constructed according to the above tests, and adsorption simulations were subsequently performed by using the models. In the CH 4 adsorption simulation, the adsorption capacity decreased after acidification, and the changing trend was highly consistent with the isothermal adsorption tests. In the simulation of the adsorption of H 2 O molecules and gas−water binary components, the macromolecular model of acidified coal exhibited better performance in absorbing H 2 O, and the improved wettability further inhibited its adsorption capacity for CH 4 . Our findings are crucial for exploring the mechanisms underlying the acid modification of wettability and adsorption capacity of coal at the microscopic level.

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Effect of acetic acid concentration and dissolution time on the evolution of coal phases: A case report of bituminous coal

Cited by 22 publications

References 39 publications

Experimental research on the influence of acid on the chemical and pore structure evolution characteristics of Wenjiaba tectonic coal

Experimental research on the influence of acid on the chemical and pore structure evolution characteristics of Wenjiaba tectonic coal

Porosity and Fracture Changes of Bituminous Coal under Action of Dry–Wet Cycles in Acid Environment

Construction of Macromolecular Structural Models of Coal and Simulation of Adsorption under Acidification

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