FTIR STUDY OF PURE VITRAINS AND ASSOCIATED COALS

A semiquantitative analysis of the infrared spectra from 650 to 4000 c m(-1) of six vitrains and the coals associated with three of them is p resented. This analysis supplies information on the concentration of s everal functionalities in the samples. Relationships between infrared data and several parameters (carbon content, vitrinite reflectance, py rolysis data) are discussed. The results thus obtained contribute to a better understanding of vitrinite structure. They also help to explai n the discrepancies between rank parameters obtained from chemical ana lyses and those determined by petrographic measurements. The compariso n between the infrared data of the Cretacic-Albian vitrain from Teruel (Spain) and its associated coal reveals the unusual chemical composit ion of this vitrain. The infrared analysis of this vitrain and the vit rian from Asturias (Jurassic-Malm) shows unusual features in compariso n with ''normal'' coals. The intensity of the aliphatic peaks relative to the aromatic (A factor) in these vitrains is characteristic of imm ature samples, closer to those of type II kerogens than type III. This result agrees with the perhydrous character of these samples and help s to explain volatile matter and pyrolysis data. However, for the vitr ain from Asturias, the intensity of the bands due to aromatic hydrogen and the ratio between aromatic and aliphatic hydrogen are consistent with a stage of evolution that is higher than the diagenesis/catagenes is transition in agreement with other chemical and petrographic data. In the vitrains from Asturias and Teruel an absorption band at 1500 cm (-1) is assigned to aromatic C=C bonds. In these vitrains, the band ce ntered at 815 cm(-1) is the most prominent in the 900-700 cm(-1) regio n. These spectral features are unusual in coal spectra, but they seem to be characteristic of perhydrous coals.