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Changes in the macromolecular structure of coals with pyrolysis temperature

Lookup NU author(s): Dr Francis Ndaji, Emeritus Professor Mark ThomasORCiD


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This paper describes a study of the effect of pyrolysis temperature on the macromolecular structure of coal, using solvent swelling techniques. Heat treatment initially dissociates the intermolecular interactions in the coal and cleaves some cross-links, leading to increase in the solvent swelling of the coal, which indicates a decrease in the cross-link density. The solvent swelling reaches a maximum before cross-linking reactions predominate, causing a progressive increase in cross-link density and a decrease in solvent swelling. For lower-rank coals there appears to be an overlap (near the temperature of minimum cross-link density) of the dissociation of intermolecular interactions and thermal decomposition. Appreciable decrease in the apparent cross-link density of high-rank coals as indicated by increase in solvent swelling was observed only after thermal decomposition had commenced. Major decomposition involves cross-linking reactions leading to the formation of chars. However, the solvent swelling characteristics continue to change above the resolidification temperature, eventually ceasing at ∼600°C. The results are discussed in relation to measurements of thermoplastic properties and devolatilization characteristics. Copyright © 1997 Elsevier Science Ltd.

Publication metadata

Author(s): Ndaji FE, Butterfield IM, Thomas KM

Publication type: Article

Publication status: Published

Journal: Fuel

Year: 1997

Volume: 76

Issue: 2

Pages: 169-177

Print publication date: 01/01/1997

ISSN (print): 0016-2361

ISSN (electronic): 1873-7153

Publisher: Elsevier Ltd


DOI: 10.1016/S0016-2361(96)00175-5


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