The smaller molecules obtainable from coal and their significance: Part 1. Solvent extraction of a weakly-caking coal at atmospheric pressure

Spence, J. A.; Vahrman, M.

doi:10.1016/s0016-2361(70)80004-7

Cited by 26 publications

(4 citation statements)

References 6 publications

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“…Coal being so heterogeneous and, thus, complex, it is rather difficult to characterize and know exactly its molecular structure. Hence, to date, none of the many proposed models (Spackman 1958;Given 1960Given , 1976Spence and Vharman 1970;Vharman 1970;Wiser 1973;Larsen and Kovac 1978;Solomon 1981;van Krevelen 1981;Gavalas 1982;Marzec 1986;Hüttinger and Mchenfelder 1987;Lucht and Pepas 1987;Solomon et al 1988;Rouzaud 1990;Carlson 1991;Carlson and Grannoff 1991;Muntean and Stock 1991;van Heek et al 1994;Kovac and Larsen 1997) has been accepted by the overall scientific community. The molecular structure of coal has been studied critically in several articles (Davidson 1982;Green et al 1982;Given 1984;Berkwitz 1987;Gorbaty 1994).…”

Section: Carbonization and Demineralization Of Coals: A Study By Meanmentioning

confidence: 99%

“…Coal seems to consist of a three-dimensional network of chains formed by aromatic and hydro-aromatic *Author for correspondence units. Chains join themselves by covalent bonds, hydrogen bonds or Van der Waals forces (Spence and Vharman 1970;Vharman 1970;van Krevelen 1981;Lucht and Pepas 1987). Inside the three-dimensional network there are some lower-weighted molecular fragments, lightly bonded to or physically trapped into the pore system (macro-, meso-and micropores) of coal.…”

Section: Carbonization and Demineralization Of Coals: A Study By Meanmentioning

confidence: 99%

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Carbonization and demineralization of coals: A study by means of FT-IR spectroscopy

et al. 2003

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Coal basically consists of two parts-a crystalline, inorganic part, and an amorphous, organic part. Based on this, we intended to study the changes that occurred on the composition and on the chemical structure of coals after carbonization at 1000 or 900°°C and demineralization treatments with hydrochloric and hydrofluoric acids. For this, four coals of different categories (or levels) were chosen: semianthracite (A-O) and high volatile bituminous coal (B-O), which are high level coals, and lignite (Li-O) and leonardite (Le-O), these being low level coals. The coals were first analysed in terms of their proximate and elemental compositions and then carbonized and demineralized. Also, the starting coals and the prepared samples were examined by infrared spectroscopy. In addition, a study of the optimization of the application of this technique for only A-O was carried out. For A-O and B-O, the spectra recorded intense absorption bands that are ascribable to vibration modes in mineral components as quartz and aluminosilicates, such as kaolinite. For Li-O and Le-O, the spectra displayed some other bands as well, also quite intense, which have been assigned to bond vibrations in functional groups and structures of their organic part. The carbonization of the coals resulted in significant changes in their inorganic part as the content of quartz increased and the content of aluminosilicates decreased. In addition, the thermal decomposition of mineral carbonates occurred. The carbonization greatly affects the organic part of the coals, especially in Li-O and Le-O, as most functional groups and structures are not thermally stable under heating conditions. With regard to demineralization, HF is a more effective agent than HCl, achieving products with higher organic content. The mass losses are higher in Li-O and Le-O than in A-O and B-O. So, the infrared spectroscopy allows the analysis of both inorganic and organic parts of the coals and of their carbonization and demineralization products. These processes facilitate subsequent analysis of the inorganic and organic parts of coals by infrared spectroscopy. In the application of this technique, both the coal : KBr ratio and the thickness for the disks should be controlled, owing to the influence on the infrared absorption.

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Section: Carbonization and Demineralization Of Coals: A Study By Meanmentioning

confidence: 99%

Section: Carbonization and Demineralization Of Coals: A Study By Meanmentioning

confidence: 99%

Carbonization and demineralization of coals: A study by means of FT-IR spectroscopy

et al. 2003

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“…This heterogeneity leads to difficulties in accurately characterizing its structure, and there is no universally accepted model for the molecular structure of coal. However, it appears to have been generally accepted that coal consists of alkyl chain substituted aromatic and hydroaromatic units linked by covalent bonds and noncovalent bonds such as hydrogen bonding and van der Waals interactions, with entanglements of skeletal chain structure to form a three-dimensional network structure. − Apart from its three-dimensional cross-linked macromolecular structure, coal is viscoelastic and partially dissolves in, and swells when exposed to, some solvents (pyridine, quinoline, 2-methylpyrrolidinone or in combination with carbon disulfide, and so on). The extent of swelling is thought to be controlled by the cross-link density and the magnitude of interaction of coal macromolecule with the solvent. − …”

Section: Introductionmentioning

confidence: 99%

A Novel Orthogonal Microscope Image Analysis Method for Evaluating Solvent-Swelling Behavior of Single Coal Particles

et al. 1998

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A novel orthogonal microscope image analysis method was developed to observe and evaluate quantitatively the dynamic solvent-swelling behavior and characteristics of coal particles separated using density gradient centrifugation technique. The important results obtained using the new method are as follows: (1) The maximum statistic probability of anisotropic swelling ratio from 1.1 to 1.3 measured in this work agrees very well with the data measured by Cody et al.; in addition, the samples with high vitrinite concentrate and high swelling ratios seem to have high anisotropic swelling feature. (2) The existence of a characteristic distribution of volumetric swelling ratio in the vitrinite concentrates strongly suggests the existence of a characteristic distribution of the molecular weight between cross-link points. (3) The average volumetric swelling ratios measured using the new method are comparable to that measured by the traditional packed bed method. (4) The simulated results using modified Painter's disinterspersion model based on the measured characteristic swelling ratios suggest that each cluster has aromatic and hydroaromatic rings from 1 to 3 in PDC-HV coal and from 1 to 5 in Witbank coal. Moreover, the relatively short average virtual bond length per carbon atom and the random walk of the chains are the main features of the coals in pyridine. (5) Although the case II and super-case II are dominant as for diffusion of pyridine in the coal particles, a few cases of Fickian and anomalous diffusion are also existing for two kinds of coal. In addition, because the value of diffusion exponents, n, of some PDC-HV coal samples changes from 0.22 to 0.39, which does not match to any classical diffusion mechanism, it seems to be the reflection of one diffusion mechanism.

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“…Vahrman et al (30,32,37,42,43) in their several investigations have established that molecules with molecular weights of less than 1000 exist in bituminous coal in quantities larger than so far believed to be present. These molecules have been classified into two categories.…”

Section: Chemical Constitution Of Coalmentioning

confidence: 99%

Liquid Fuels and Chemical Feedstocks from Coal by Supercritical Gas Extraction

Gangoli¹,

Thodos²

1977

Product R&D

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He received his B.Tech (Honors) from Osmania University, India, in 1970, and his M.S. from Northwestern University in 1971. He has co-authored four papers in the water pollution area. His research interests are in environmental sciences, thermodynamics, and synthetic fuels. Mr. Gangoli is a member of the American Institute of Chemical Engineers, Sigma Xi, and Tau Beta Pi; he will be joining the Environmental Control

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The smaller molecules obtainable from coal and their significance: Part 1. Solvent extraction of a weakly-caking coal at atmospheric pressure

Cited by 26 publications

References 6 publications

Carbonization and demineralization of coals: A study by means of FT-IR spectroscopy

Carbonization and demineralization of coals: A study by means of FT-IR spectroscopy

A Novel Orthogonal Microscope Image Analysis Method for Evaluating Solvent-Swelling Behavior of Single Coal Particles

Liquid Fuels and Chemical Feedstocks from Coal by Supercritical Gas Extraction

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