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Effects of coal molecular structure and pore morphology on methane adsorption and accumulation mechanism

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Frontiers of Earth Science 2023年第1期17卷 262-272页

作者： Jingshuo ZHANG Xiaoming NI Ying HAN Junfeng LIN School of Energy Science and Engineering Henan Polytechnic UniversityJiaozuo 454000China

The adsorption,diffusion,and aggregation of methane from coal are often studied based on slit or carbon nanotube models and isothermal adsorption and thermodynamics theories.However,the pore morphology of the slit model involves a single slit,and the carbon nanotube model does not consider the molecular structure of coal.The difference of the adsorption capacity of coal to methane was determined without considering the external environmental conditions by the molecular structure and pore morphology of coal.The study of methane adsorption by coal under single condition cannot reveal its mechanism.In view of this,elemental analysis,FTIR spectrum,XPS electron energy spectrum,13C NMR,and isothermal adsorption tests were conducted on the semi-anthracite of Changping mine and the anthracite of Sihe Mine in Shanxi Province,China.The grand canonical Monte Carlo(GCMC)and molecular dynamics simulation method was used to establish the coal molecular structure model.By comparing the results with the experimental test results,the accuracy and practicability of the molecular structure model are confirmed.Based on the adsorption potential energy theory and aggregation model,the adsorption force of methane on aromatic ring structure,pyrrole nitrogen structure,aliphatic structure,and oxygen-containing functional group was calculated.The relationship between pore morphology,methane aggregation morphology,and coal molecular structure was revealed.The results show that the adsorption force of coal molecular structure on methane is as follows:aromatic ring structure(1.96 kcal/mol)>pyridine nitrogen(1.41 kcal/mol)>pyrrorole nitrogen(1.05 kcal/mol)>aliphatic structure(0.29 kcal/mol)>oxygen-containing functional group(0.20 kcal/mol).In the long and narrow regular pores of semi-anthracite and anthracite,methane aggregates in clusters at turns and aperture changes,and the adsorption and aggregation positions are mainly determined by the aromatic ring structure,the positions of pyrrole nitrogen and pyridine nitrogen.The degree of aggregati

关键词： Grand Canonical Monte Carlo pore morphology methane adsorption molecular structure of coal

Behavior and controlling factors of methane adsorption in Jurassic continental shale,northeastern Sichuan Basin

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能源地球科学(英文)

能源地球科学(英文) 2023年第1期4卷 83-92页

作者： Qian-wen Li Zhong-bao Liu Fei-Ran Chen Kun Zhang Ling Tang Sinopec Petroleum Exploration and Production Research Institute Beijing102206China Sinopec Southern Company of Exploration ChengduSichuan 610041China School of Geoscience and Technology Southwest Petroleum UniversityChengduSichuan 610059China CNOOC Research Institute Ltd. Beijing100029China

The behavior and controlling factors of natural gas adsorption in the Jurassic continental shale in the northeastern Sichuan Basin are studied based on the organic geochemical features,mineral compositions and pore structure parameters through a series of experiments on samples from the shale.Results show that the total gas content of the shale measured on-site is 0.1-5.3 cm^(3)/g,with an average of 0.7 cm^(3)/g.The methane isothermal adsorption curves show a trend of increasing first and then decreasing,indicating an obvious excessive adsorption.The shale has a maximum adsorption capacity(V^(L))of 0.44-3.59 cm^(3)/g,with an average of 1.64 cm^(3)/g,lower than that of marine shale in the same basin.The organic matter content and pore structure characteristics are identified as the two main factors controlling the adsorption capacity of the shale.Micropores in the shale are the main storage space for gas to be adsorbed.Due to well developed shell laminae and interlayers in the shale,calcite plays a more important role than clay minerals in affecting the adsorption of gas to the rock.The formation temperature and water content also significantly inhibit the gas adsorption to the shale.Compared with marine shale in the basin,the Jurassic continental shale is more heterogeneous and lower in TOC values.Furthermore,with a more widely developed clayey shale lithofacies and shell limy shale lithofacies as well as relatively less developed organic pores and micropores,the continental shale is inferior to marine shale in terms of gas adsorption capacity.

关键词： methane adsorption Controlling factors Continental shale Jurassic Sichuan basin

Main controlling factor and mechanism of gas-in-place content of the Lower Cambrian shale from different sedimentary facies in the western Hubei area, South China

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Petroleum Science 2024年第3期21卷 1488-1507页

作者： Gang Li Xian-Ming Xiao Bo-Wei Cheng Chen-Gang Lu Yue Feng Dong-Sheng Li School of Energy Resources China University of Geosciences (Beijing) Frontiers Science Center for Deep-time Digital Earth China University of Geosciences (Beijing)

The Lower Cambrian shale gas in the western Hubei area, South China has a great resource prospect, but the gas-in-place（GIP） content in different sedimentary facies varies widely, and the relevant mechanism has been not well understood. In the present study, two sets of the Lower Cambrian shale samples from the Wells YD4 and YD5 in the western Hubei area, representing the deep-water shelf facies and shallowwater platform facies, respectively, were investigated on the differences of pore types, pore structure and methane adsorption capacity between them, and the main controlling factor and mechanism of their methane adsorption capacities and GIP contents were discussed. The results show that the organic matter（OM） pores in the YD4 shale samples are dominant, while the inorganic mineral（IM） pores in the YD5 shale samples are primary, with underdeveloped OM pores. The pore specific surface area（SSA） and pore volume（PV） of the YD4 shale samples are mainly from micropores and mesopores, respectively,while those of the YD5 shale samples are mainly from micropores and macropores, respectively. The methane adsorption capacity of the YD4 shale samples is significantly higher than that of the YD5 shale samples, with a maximum absolute adsorption capacity of 3.13 cm3/g and 1.31 cm3/g in average,respectively. Compared with the shallow-water platform shale, the deep-water shelf shale has a higher TOC content, a better kerogen type and more developed OM pores, which is the main mechanism for its higher adsorption capacity. The GIP content models based on two samples with a similar TOC content selected respectively from the Wells YD4 and YD5 further indicate that the GIP content of the deep-water shelf shale is mainly 3 4 m3/t within a depth range of 1000—4000 m, with shale gas exploration and development potential, while the shallow-water platform shale has normally a GIP content of <1 m3/t,with little shale gas potential. Considering the geological and geochemical conditions of shale gas formation and preservation, the deep-w

关键词： Lower Cambrian shale Deep-water shelf facies Shallow-water platform facies Pore structure methane adsorption Gas-in-place content Controlling factor

adsorption Isotherm and Kinetic Study of methane on Palm Kernel Shell-Derived Activated Carbon

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Journal of Bioresources and Bioproducts 2023年第1期8卷 66-77页

作者： Mohd Saufi Md Zaini Muhammad Arshad Syed Shatir A.Syed-Hassan School of Chemical Engineering College of EngineeringUniversiti Teknologi MARA Cawangan TerengganuKampus Bukit BesiDungun 23200Malaysia Department of Basic Science Jhang-Campus University of Veterinary and Animal ScienceLahore 35200Pakistan School of Chemical Engineering College of EngineeringUniversiti Teknologi MARAShah Alam 40450Malaysia

Activated carbon(AC)was synthesized from palm kernel shell(PKS)using different activating agents,i.e.,steam,carbon dioxide(CO 2),and CO 2-steam,in order to analyze the impact of acti-vating agents on the pore opening of AC.In this study,AC produced from PKS was found to have great potential as an adsorbent for methane storage.The different molecular diffusivity and reac-tivity of the combination of CO 2 and steam succeeded in producing AC with the highest burn-offof 78.57%,a surface area of 869.82 m 2/g,a total pore volume of 0.47 cm 3/g,and leading to maximum methane gas adsorption capacity of 4.500 mol/kg.All types of ACs exhibited the best fit with the Freundlich isotherm model,with the correlation coefficient(R 2)ranging from 0.997 to 0.999,indicating the formation of multilayer adsorption.In addition,the adsorption kinetic data for all ACs followed the pseudo-first-order model showing that the rate of adsorption was dependent on both the adsorbent and the adsorbate and was governed primarily by physical ad-sorption between the pore surface and methane gas.The results of intraparticle diffusion model indicated that the adsorption of methane was affected by both pore diffusion and exterior layer diffusion due to the different adsorption rates.

关键词： Palm kernel shell Activated carbon methane adsorption Kinetic model Isotherm model

K_2S-activated carbons developed from coal and their methane adsorption behaviors

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Chinese Physics B 2014年第10期23卷 573-580页

作者：冯艳艳杨文储伟 Department of Chemical Engineering Sichuan University

The main purpose of this work is to prepare various activated carbons by K2S activation of coal with size fractions of 60-80 meshes, and investigate the microporosity development and corresponding methane storage capacities. Raw coal is mixed with K2S powder, and then heated at 750 ℃-900 ℃ for 30 min-150 min in N2 atmosphere to produce the adsorbents. The texture and surface morphology are characterized by a N2 adsorption/desorption isotherm at 77 K and scanning electron microscopy （SEM）. The chemical properties of carbons are confirmed by ultimate analysis. The crystal structure and degree of graphitization are tested by X-ray diffraction and Raman spectra. The relationship between sulfur content and the specific surface area of the adsorbents is also determined. K2S activation is helps to bring about better development of pore texture. These adsorbents are microporous materials with textural parameters increasing in a range of specific surface area 72.27 m2/g-657.7 m2/g and micropore volume 0.035 cm3/g-0.334 cm3/g. The ability of activated carbons to adsorb methane is measured at 298 K and at pressures up to 5.0 MPa by a volumetric method. The Langmuir model fits the experimental data well. It is concluded that the high specific surface area and micropore volume of activated carbons do determine methane adsorption capacity. The adsorbents obtained at 800 ℃ for 90 min with K2S/raw coal mass ratios of 1.0 and 1.2 show the highest methane adsorption capacities amounting to 106.98 mg/g and 106.17 mg/g, respectively.

关键词： coal K2S activation microporosity methane adsorption

Pore structure characterization and its effect on methane adsorption in shale kerogen

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Petroleum Science 2021年第2期18卷 565-578页

作者： Tian-Yu Wang Shou-Ceng Tian Qing-Ling Liu Gen-Sheng Li Mao Sheng Wen-Xi Ren Pan-Pan Zhang State Key Laboratory of Petroleum Resources and Prospecting China University of Petroleum(Beijing)Beijing102249China Harvard SEAS-CUPB Joint Laboratory on Petroleum Science 29 Oxford StreetCambridgeMA02138USA China National Oil and Gas Exploration and Development Company Ltd Beijing100034China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum UniversityChengdu610500China

Pore structure characterization and its effect on methane adsorption on shale kerogen are crucial to understanding the fundamental mechanisms of gas storage,transport,and reserves evaluation.In this study,we use 3D scanning confocal microscopy,scanning electron microscopy(SEM),X-ray nano-computed tomography(nano-CT),and low-pressure N2 adsorption analysis to analyze the pore structures of the shale.Additionally,the adsorption behavior of methane on shales with different pore structures is investigated by molecular simulations.The results show that the SEM image of the shale sample obviously displays four different pore shapes,including slit pore,square pore,triangle pore,and circle pore.The average coordination number is 4.21 and the distribution of coordination numbers demonstrates that pores in the shale have high connectivity.Compared with the adsorption capacity of methane on triangle pores,the adsorption capacity on slit pore,square pore,and circle pore are reduced by 9.86%,8.55%,and 6.12%,respectively.With increasing pressure,these acute wedges fill in a manner different from the right or obtuse angles in the other pores.This study offers a quantitative understanding of the effect of pore structure on methane adsorption in the shale and provides better insight into the evaluation of gas storage in geologic shale reservoirs.

关键词： Shale methane adsorption Pore structure Kerogen Molecular simulation

Surface Modification of Bituminous Coal and Its Effects on methane adsorption

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Chinese Journal of Chemistry 2013年第8期31卷 1102-1108页

作者： Yanyan Feng Wen Yang Daijun Liu[*] Wei Chu[*] Department of Chemical Engineering Sichuan University Chengdug Sichuan 610065 China Email: Daijun Liu (liudj721@***) Wei Chu (chuwei1965scu@***)[*]Department of Chemical Engineering Sichuan University Chengdug Sichuan 610065 China Tel.: 0086-028-8540 3836

This paper studied the role of O-containing groups over the coal surface in methane adsorption. The coal was modified with H2SO4, （NH4）2S208 or H2SO4/（NH4）2S2Os）, respectively, to introduce O-containing functional groups, and characterized by proximate analysis, ultimate analysis, Boehm titration, X-ray photoelectron spectroscopy （XPS） and nitrogen adsorption. The results of ultimate analysis, Boehm titration and XPS indicate that there were increases in terms of both the content of oxygen and the quantities of O-containing groups over the modified coals surface, especially for the carboxyl. Nitrogen adsorption shows that the modified coals possessed higher surface area and pore volume than that of 0-XQ. The methane adsorption data were measured at 298 K at pressures up to 4.0 MPa by the volumetric method and fitted well by Langmuir model. Experimental results implied that O-containing groups and pore structure affected methane adsorption. The adsorption capacities decreased as increasing quantities of O-containing groups.

关键词： modification O-containing groups pore structure methane adsorption

methane adsorption AT LOW TEMPERATURE OVER HZSM-5 ZEOLITE AND Mo/HZSM-5

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Chinese Journal of Catalysis 1995年第1期 5-6页

作者： Chen. Lai-yuan Lin. Li-wu Xin. Qin Xu. Zhu-sheng Zhang, Tao Ying, Pin-Hang Li, Guo-qiang and Li, Can(Laboratory of Catalysis by Metals and New Materials, Stale Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116C23)

The recent development of methane conversion over HZSM-5 and Mo/NZSM-5 arouses great interest .As these catalysts are strong solid acidin nature,it is thus speculated that the reaction mechanism is different fromthose of OCM and partial oxidation of methane.Therefore,the study on theinteraction of methane with their surfaces is of importance to the under-standing of the new route of methane conversion.

关键词： methane adsorption HZSM-5 Mo/HZSM-5 IR spectra

Theoretical and Experimental Study on the adsorption and Desorption of methane by Granular Activated Carbon at 25℃

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Journal of Natural Gas Chemistry 2007年第4期16卷 415-422页

作者： E.Salehi V.Taghikhani C.Ghotbi E.Nemati Lay A.Shojaei Department of Chemical and Petroleum Engineering Sharif University of Technology TehranIran

A theoretical and experimental study was conducted to accurately determine the amount of adsorption and desorption of methane by various Granular Activated Carbon （GAC） under different physical conditions. To carry out the experiments, the volumetric method was used up to 500 psia at constant temperature of 25℃. In these experiments, adsorption as well as desorption capacities of four different GAC in the adsorption of methane, the major constituent of natural gas, at various equilibrium pressures and a constant temperature were studied. Also, various adsorption isotherm models were used to model the experimental data collected from the experiments. The accuracy of the results obtained from the adsorption isotherm models was compared and the values for the regressed parameters were reported. The results shows that the physical characteristics of activated carbons such as BET surface area, micropore volume, packing density, and pore size distribution play an important role in the amount of methane to be adsorbed and desorbed.

关键词： methane adsorption volumetric method activated carbon two-term TVFM isotherm