Studies on Chemical Structure of Coal (II)

Comparison of carbon distribution based on pyrolysis data with those from solid state NMR data

Abstract

Authors have previously proposed a method to evaluate chemical structure of Akabira coal by combined use of pyrolysis and solid state ¹³C-NMR data. This method is to evaluate distribution of aromatic compounds using pyrolysis data of its extracts. Adjustment of distribution of aliphatic and aromatic carbons was carried out by using CP/MAS ¹³C-NMR data of raw coal.
In this method, volatile fraction of extracts in pyrolysis is assumed to represent whole constituents of the extracts. In order to examine whether above assumption is correct or not, distribution of 9 kinds of carbons in the coal, which is comparable with those from solid state NMR measurement, was calculated based on pyrolysis data. Above calculation was carried out for Illinois No.6 and Miike coals by using several assumptions (i) all alkyl aromatics are present as methylated derivatives, (ii) isomers ratio is equivalent, (iii) non protonated aromatic carbons are included in Ar-C, and (iv) aromatic carbons next to oxygen atom in benzo- and dibenzofuran are included in Ar-O. These results were compared with that of raw coal from CP/MAS ¹³C-NMR. This comparison brought about relatively good coincidence between the carbon distributions of Illinois No.6 coal from pyrolysis and NMR data, while there was a little discrepancy between these carbon distributions for Miike coal. This tendency was discussed briefly.