Macroscopic observation of thermal behavior of concentrated solution of coal extracts

Masao Suzuki, Koyo Norinaga, Masashi Iino

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5 Citations (Scopus)


The solvent extracts of Upper Freeport and Illinois No.6 coals were mixed with N-methyl-2-pyrolidinon (NMP) and annealed at 353 K to produce the gelatinous materials. Differential scanning calorimetric measurements revealed that the materials can hold significant amounts of nonfreezable NMP (as much as 3 g NMP per 1 g coal extracts) which disperse in the materials on a molecular scale, indicating the materials are not phase separated. The thermal behaviors were measured macroscopically as a function of the extract concentration using a needle penetrometer during heating from 223 to 360 K. The penetration- temperature curves were analyzed to estimate the apparent viscosity (ηa). During the penetrations, ηa was decreased very rapidly, approximately four orders of the magnitude by a temperature increase of 20 K, suggesting that the coal extracts-NMP mixtures undergoes a gel to sol transition. The heats of dissociation of crosslinks (ΔH m) were estimated by applying Eldridge-Ferry equation. The ΔHm of coal extracts-NMP mixtures was relatively small, i.e. approximately 10 kJ/mol, whereas the ΔHm of polyvinyl alcohol-NMP gel in which the hydrogen bonds contribute the formation of the physical network structures, was about 65 kJ/mol. Not the specific interaction such as hydrogen bonds, but weak interactions such as van der Waals force were likely to contribute the formation of the coal extracts-NMP gel.

Original languageEnglish
Pages (from-to)2177-2182
Number of pages6
Issue number16
Publication statusPublished - Nov 2004
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Organic Chemistry


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