Analyses of the Soluble Products of Yubari and Taiheiyo Coals Treated with Zinc and Butyl lodide

Abstract

Yubari and Taiheiyo coals were converted to hexane soluble products in high yields by the repetitive butylation using zinc and butyl iodide under mild conditions (130 °C, under atmospheric pressure). The hexane soluble products were fractionated into seven fractions by column chromatography (CC), and the CC fractions were further separated by gel permeation chromatography (GPC) to investigate the chemical structure of the solvent-soluble products and the mechanism of the coal solubilization.
The GPC fractions of both coals had high σ_al (degree of aliphatic chain substitution ) and low fa (aromaticity), because of the introduction of many butyl groups to coal aromatic moieties. The size of aromatic rings of the GPC fractions seemed to be small, 2-3 rings for Yubari coal; these small aromatic ring size may be caused by reductive butylation. The lower aliphatic chain length (L=2.1-2.9) of the GPC fractions, than expected from the introduction of many butyl groups (L = 4), also indicated the occurrence of reductive butylation. In addition, the yields (based on original coals) of the GPC fractions with average molecular weight below 800 were small 7.7 wt% for Yubari coal and 17.8 wt% for Taiheiyo coal, indicating that the linkage connecting aromatic moieties of coal was not broken so much.
These characteristics of GPC fractions indicate that the high extractabilities of the bu tylated coals with solvents are mainly caused by the reductive butylation of aromatic moieties of the colas.