Analysis of oxygen-functional groups in brown coals

Distribution of oxygen-functional groups (alcohol, phenol, carboxyl, carbonyl, and ether groups) in four brown coals, Australian Yallourn (abbreviated as YL), Indonesian South Banko (SB) and Adaro (AD), and US Beulah Zap (BZ), was evaluated based on chemical analysis and C-13 NMR measurement. Concentrations of carbonyl and ether groups were about 20%, based on total oxygen in coal, while the distribution of carboxyl, alcohol, and phenol changed from coal to coal. The evaluation of the amount of reactive ether groups was conducted by treating the sample coals with SiCl4-NaI, which is able to cleave alkylaryl- and dialkylethers. The results indicate that the sample coals contained reactive ether groups ranging from 0.3 to 1.8 groups per 100 carbon in coal. The relationships between the amounts of oxygen-functional groups and the solubility of coal were also investigated. (C) 2000 Elsevier Science B.V. All rights reserved.