Vl. Cebolla et al., STUDY OF THE REPRODUCIBILITY AND SELECTIVITY OF COAL-TAR PITCH FRACTIONATION BY EXTROGRAPHY ON ALUMINA, Fuel, 73(6), 1994, pp. 950-956
The potential of extrography on alumina as a fractionation and charact
erization technique of coal tar pitches has been evaluated in terms of
reproducibility and selectivity of separations. Parameters controllin
g extrography were carefully selected, and standard conditions were ad
opted by two different laboratories in a reproducibility study. Result
s relating to mass balances of extrography, selectivity of separation,
thermal behaviour of the separated fractions and coke characteristics
were comparable for interlaboratory runs. Selectivity of the separati
ons was followed by chemical gas chromatography-mass spectrometry (g.c
.-m.s.), nuclear magnetic resonance (n.m.r.), Fourier transform infrar
ed (FT-i.r.) spectroscopy, thin layer chromatography-FID (t.l.c.-FID)
and thermal thermogravimetric (TGA) and differential thermal analysis
(DTA)] characterizations of both fractions and subfractions collected.
Their derived cokes were studied by optical microscopy to determine t
heir respective degree of anisotropy to relate chemical structure, the
rmal reactivity and coke quality. Concerning the mechanism of extrogra
phic elution, analytical data suggest an extractive mechanism for the
first eluted fraction, and dominant chromatographic processes for the
more polar fractions.