Abrupt changes (jumps) in reflectance values and chemical compositions of artificial charcoals and inertinite in coals

Abrupt changes (jumps) in reflectance values and chemical compositions of c harcoals during heating experiments in muffle and thermal gravimetric analy zer ovens occur at mean maximum reflectance values of about 0.50-0.60%, 1.1 0-1.20%, 1.40-1.50'%, 2.20-2.30%, 2.80-2.90% and 3.70-3.90% (R-max). These abrupt changes are similar to the so called 'coalification jumps' in vitrin ite or liptinite in coals. Jumps are much more notable in low temperature c harcoals (formed at less than 400 degrees C) than in high temperature charc oals (formed at greater than 400 degrees C). Abrupt changes in chemical com position are coincident with jumps in reflectance as evident from sudden de creases or increases in functional groups as determined by FTIR-spectra. Th e jumps in composition of charcoals (intertinites) during charring experime nts explains the multi-modal reflectance distributions commonly documented in coals. The distribution of reflectance values and FTIR spectral characte ristics of inertinite in some Western Canadian coals is consistent with a m odel of charring that incorporates discrete compositional jumps. The 'jumps ' in reflectance values and chemical compositions probably reflect progress ive breaking of chemical bonds in response to attainment of specific thresh old activation energies. (C) 1999 Elsevier Science B.V. All rights reserved .