Evolution characteristics of sulfur-bearing structures of low and medium rank coal with high organic sulfur content

By means of the computer curve-fitting method, the infrared spectra data of nine medium and low-rank high organic sulfur coals were processed and the infrared spectrum characteristics were quantitatively analyzed. The results showed that the ratio of area of mercaptan (SH), double thioether (S-S) to Carbonyl which are called sulfur-bearing structures FT-IR parameters were significant positively correlated with R_max and organic sulfur content. Organic sulfur content and total sulfur ratio is affected by micro environment. In same sample, FeS₂, SH, S-S were decreased progressively in turn. The total of -SH and S-S showed mutually complementary relation with oxygen-containing functional groups, and sharply rises at the point of second coalification jump. The IR parameters of the length and degree of branching aliphatic side chains and aromatization shows that as the rank of metamorphosed coal is high, the degree of branching aliphatic side chains decreased and the extent of aromatization increased, consistent with evolution characteristics of general low sulfur coals.