1H n.m.r. evidence to support the host/guest model of brown coals☆

Lynch, Leo J.; Sakurovs, Richard; Webster, David; Redlich, Peter J.

doi:10.1016/0016-2361(88)90367-5

Cited by 42 publications

(22 citation statements)

References 5 publications

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“…Following those studies, the present authors [8][9][10][11] proposed binderless briquetting of lignite at temperature up to 200°C by taking advantage of its thermophysical behavior; a sort of plasticization that is arisen from local mobility of relatively flexible macromolecular network. [12][13][14] The hot briquetting enabled to prepare highly densified briquettes from a Victorian lignite. 8) Subsequent carbonization by heating the briquettes up to 900°C transformed them into cokes with tensile strength ranging from 20 to 40 MPa.…”

Section: Introductionmentioning

confidence: 99%

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Production of High-strength Cokes from Non-/Slightly Caking Coals. Part I: Effects of Coal Pretreatment and Variables for Briquetting and Carbonization on Coke Properties

et al. 2019

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In continuation of the present authors' studies on production of high strength coke from lignite by sequential binderless hot briquetting and carbonization, this study has been carried out aiming at proposing methods to produce high strength coke from non-/slightly caking coals of subbituminous to bituminous rank. This paper firstly demonstrates preparation of cokes with cold tensile strengths above 10 MPa from two single non-caking coals (particle size; < 106 μm) by applying briquetting at temperature and mechanical pressure of over 200°C and 100 MPa, respectively. Such strength of coke is obtained over a wide range of heating rate, 3-30°C/min, during carbonization with final temperature of 1 000°C. Then, a simple pretreatment, fine pulverization of coal to particle sizes smaller than 10 or 5 μm, is examined. This pretreatment enables to prepare coke with tensile strength even over 25 MPa, by decreasing porosity of resulting coke and more extensively the size of macropores simultaneously. The coke strength changes with carbonization temperature having a particular feature; significant development of strength at 600-1 000°C, i.e., after completion of tar evolution, in which macropores and non-porous (dense) part of coke shrink in volume, inducing bonding and coalescence of particles and thereby arising the strength.

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Section: Introductionmentioning

confidence: 99%

“…On the other hand, it is believed that organic matrices of subbituminous/bituminous coals are less plasticizable than lignites at temperature as low as 100-200°C. 12,13) It may therefore be necessary to introduce a reasonable and effective pretreatment before the briquetting.…”

Section: Introductionmentioning

confidence: 99%

Production of High-strength Cokes from Non-/Slightly Caking Coals. Part I: Effects of Coal Pretreatment and Variables for Briquetting and Carbonization on Coke Properties

et al. 2019

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“…It is well agreed that stress relaxation of becomes more extensive and rapid as the temperature increases. 9) Figure 3 exhibits SEM photographs of polished fractured surfaces from cokes prepared from W-FP coals (except W-FP IS) with T b = 40°C. The porous nature of coke is qualitatively evaluated from the photographs.…”

Section: Cokes From Single Coalsmentioning

confidence: 99%

Production of High-strength Cokes from Non- and Slightly Caking Coals. Part II: Application of Sequence of Fine Pulverization of Coal, Briquetting and Carbonization to Single Coals and Binary Blends

et al. 2019

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Sequential coal briquetting and carbonization was applied to preparation of cokes from 9 non-or slightly caking coals with carbon contents (f C) of 67-85 wt%-daf. Coal pulverization to sizes of < 106 μm and briquetting at 40°C enabled to prepare cokes with tensile strength (σ) over 10 MPa from 4 coals with f C of 82-85 or 67 wt%-daf. Then, by introducing fine pulverization to sizes of < 10 μm before the briquetting, 7 coals were converted successfully into cokes with σ = 11-25 MPa. Increasing the briquetting temperature to 240°C further increased σ to 19-35 MPa for all the 9 coals. It was thus demonstrated that the hot briquetting of finely pulverized coal was a method to prepare high strength coke regardless of the rank of parent coal. Cokes were also prepared from 14 binary coal blends. All the cokes prepared by applying the fine pulverization and hot briquetting had σ of 20-35 MPa, which agreed well with that calculated by weighted average of those from the component coals. On the other hand, positive and also negative synergistic effects of blending occurred when blends were briquetted at 40°C. Characteristics of bonding/ coalescence among particles of different types of coals were responsible for such synergies.

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“…A physically associated coal model was set against the molecular/macromolecular model. Evidence to date suggests that the molecular/macromolecular model might apply to lignites, brown coals and sub-bituminous coals [55,56], but not so well to bituminous coals. While the debate on these opposite structure models is continuing, new 1 H NMR experiments appear to reveal that a correlation between molecular mobility derived from proton relaxation times and molecular/macromolecular phases is much more complicated than previously thought [52,53].…”

Section: Organic Structurementioning

confidence: 99%

“…There coal is regarded as a mono-phase of associated macromolecules with average molar masses in the order of a few thousand g mol −1 and a network structure is held together mainly by non-covalent bonds, which include ionic forces, hydrogen bonding, charge-transfer and aromatic π -π interactions [10,[47][48][49][50][51]. The average molecular size and the cross-linking in bituminous coals seem to decrease with increasing rank to a minimum at around 86% carbon [55][56][57]. Moreover, the characterization of solvent-swollen coal by proton spin diffusion and small-angle neutron scattering indicated that part of the volume expansion in solvent swelling is related to a formation of nanoscalic phase-separated domains, and this micro-heterogeneity makes the application of statistical mechanical theories to the swelling of coal dubious [54].…”

Section: Organic Structurementioning

confidence: 99%

Catalysis in Direct Coal Liquefaction

Haenel¹

2008

Handbook of Heterogeneous Catalysis

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The sections in this article are Introduction Coal Structure Organic Structure Inorganic Structure Physical Structure Fundamental Transformations in Direct Coal Liquefaction Coal Properties Primary Liquefaction Products Solvent Catalysis in Direct Coal Liquefaction Dissolution Catalysts in the First Liquefaction Stage Supported Catalysts Dissolved Catalysts Perspectives for Direct Coal Liquefaction

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1H n.m.r. evidence to support the host/guest model of brown coals☆

Cited by 42 publications

References 5 publications

Production of High-strength Cokes from Non-/Slightly Caking Coals. Part I: Effects of Coal Pretreatment and Variables for Briquetting and Carbonization on Coke Properties

Production of High-strength Cokes from Non-/Slightly Caking Coals. Part I: Effects of Coal Pretreatment and Variables for Briquetting and Carbonization on Coke Properties

Production of High-strength Cokes from Non- and Slightly Caking Coals. Part II: Application of Sequence of Fine Pulverization of Coal, Briquetting and Carbonization to Single Coals and Binary Blends

Catalysis in Direct Coal Liquefaction

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