Characterization of porosity via secondary reactions. Quarterly technical progress report, 1 April 1995--30 June 1995 Page: 4 of 20
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1.0. PROJECT BACKGROUND
1.1. Overview.
Specific surface area, as well as its accessibility to gaseous reactants, are of
paramount importance for all heterogeneous interactions occurring at coal char
surfaces. Accessibility of this surface area is governed by the pore structure
morphology of the char; i.e., pore size distribution, tortuosity, intersections,
shape, etc. The porosity morphology of coal chars varies over a considerable
range and is determined by a large number of factors including the nature of the
porosity of the precursor material prior to carbonization, the carbonization
process, and extent and method of any subsequent activation or gasification. A
persistent problem in this area has been the reliable, quantitative measurement
and characterization of the resultant porosity, especially the micropores. For
example, electron microscopy tends to be qualitative; small angle X-ray or small
angle neutron scattering (SAXS/SANS) can suffer from sensitivity to interpretive
models, and the inability to distinguish porosity that communicates with the
surface from that which does not; and gas adsorption techniques also have several
well known drawbacks. The latter, however, are perhaps the most reliable in
general, but yield pore size distributions indirectly via surface area and pore
volume measurements, and can also be laborious and time-consuming. Therefore,
there is still a critical need for practical and facile techniques to characterize the
porosity of coal chars.
1.2. The Current Project.
The current project is directed at the development of a new approach to
this very old problem. During the course of recent work applying temperature
programmed desorption (TPD) to the determination of energetic distributions of
oxygen complexes on the surfaces of oxidized coal chars (Calo et al., 1989,2
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Calo, J.M.; Hall, P.J.; Antxustegi, M.M. & Zhang, L. Characterization of porosity via secondary reactions. Quarterly technical progress report, 1 April 1995--30 June 1995, report, December 31, 1995; Providence, Rhode Island. (https://digital.library.unt.edu/ark:/67531/metadc667788/m1/4/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.