Molecular size and structure in pyridine extracts of upper Freeport coal as separated by M41S sieving.

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The determination of the structure of coal has long been of interest due to its crucial importance in research on reactivity and processing. However, the chemically and physically heterogeneous nature of coals makes determination of the chemical nature of even the building blocks complicated, since the molecular structure and molecular weight distribution are not dependent on a single molecule or repeat unit as in technical polymers or biopolymers, but on a complex mixture of molecules and potential connections between them which may vary among coals. Coal extracts have long been used to obtain coal material in solution form that can ... continued below

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7 p.

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Ahrens, M.; Hunt, J. E.; Winans, R. E. & Xu, L. July 2, 1999.

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The determination of the structure of coal has long been of interest due to its crucial importance in research on reactivity and processing. However, the chemically and physically heterogeneous nature of coals makes determination of the chemical nature of even the building blocks complicated, since the molecular structure and molecular weight distribution are not dependent on a single molecule or repeat unit as in technical polymers or biopolymers, but on a complex mixture of molecules and potential connections between them which may vary among coals. Coal extracts have long been used to obtain coal material in solution form that can readily be characterized. However, what part of the total coal structure these extracts represent is not completely known. Pyridine has been a particularly good solvent for coal; for example, the extractability of Upper Freeport has been shown to be as high 30%. Although pyridine extracts of coal have been referred to as solutions, there is good evidence that they are not truly solvated, but are dispersions which are polydisperse in particle size. The particle sizes may span the size range from clusters of small molecules (a few {angstrom}) to extended clusters of large particles (a few hundred {angstrom}), not unlike micelles, where the functional groups of molecules which interact favorably with the pyridine solvent lie at the surface of particles. Mesoporous silicates are attractive candidates for separations due to their high surface areas and porous nature. MCM-41 is one member of a new family of highly uniform mesoporous silicate materials introduced by Mobil, whose pore size can be accurately controlled in the range 1.5{angstrom}-10 nm. This recently discovered M41S class of zeolites should be useful to effect size separation, due to their large pore sizes and thus their potential for the separation of larger compounds or clusters. True molecular sieving on the size range of molecular and cluster types found in coal solutions should be possible with M41S materials by tuning the pore size. We have synthesized a mesoporous silicate material with a surface area of approximately 1100 m{sup 2}/g and pore sizes of approximately 25 {angstrom} and 33 {angstrom}. The results of a study on the ability of this mesoporous materials (M41S) to be used as stationary phases for separations of coal complexes in pyridine is the subject of this paper.

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7 p.

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OSTI as DE00011783

Medium: P; Size: 7 pages

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  • 218th American Chemical Society National Meeting, New Orleans, LA (US), 08/22/1999--08/26/1999

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  • Report No.: ANL/CHM/CP-98923
  • Grant Number: W-31109-ENG-38
  • Office of Scientific & Technical Information Report Number: 11783
  • Archival Resource Key: ark:/67531/metadc623902

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  • July 2, 1999

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  • June 16, 2015, 7:43 a.m.

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  • April 11, 2017, 3:35 p.m.

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Ahrens, M.; Hunt, J. E.; Winans, R. E. & Xu, L. Molecular size and structure in pyridine extracts of upper Freeport coal as separated by M41S sieving., article, July 2, 1999; Illinois. (digital.library.unt.edu/ark:/67531/metadc623902/: accessed September 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.