Abstract: By means of in-situ diffuse reflectance FTIR, the IR spectra of 6 coals with different ranks were obtained from room temperature to 230 ℃. A new curve fitting method was used to recognize the different hydrogen bonds in the coals, and the influence of coal ranks on the distribution of hydrogen bonds(HBs) in the coals and their thermal stability were discussed. The results show that there is another new HB(around 2514 cm^-1) between the -SH in mercaptans or thiophenols and the nitrogen in the pyridine-like compounds in the coals, and the evidence for that was provided. The controversial band of the HB between hydroxyl and the nitrogen of the pyridine-like compounds was determined in the range of 3028-2984 cm^-1, and the result is consistent with but more specific than that of Painter et al.. It was found that the stability of different HBs in the coals is influenced by both coal rank and temperature. For some HBs, the higher the coal rank, the higher the stability of them. Within the temperature range of our research, the stability of the HB between the hydroxyl and the π bond increases to some extent for some coals at temperatures higher than 110 or 140 ℃.

Key words: Hydrogen bonding, Thermal stability, Coal rank, Coal, In-situ diffuse reflectance FTIR