Analysis of organic compounds in coal macerals by infrared laser micropyrolysis

Laser micropyrolysis combined with gas chromatography-mass spectrometry (GC-MS) was used for analyzing organic compounds in three macerals of an immature, sub-bituminous coal: telocollinite, dearadinite, and cutinite. To limit thermal effects on the area surrounding the irradiation point, we shortened the irradiation duration by using a pulsed laser, and we used an aperture to cut off the edge of the laser beam. Aromatic hydrocarbons such as phenol, cresol, and methylguaiacol were the main compounds detected in telocollinite. Prist-1-ene, a series of n-alkaneshi-alkenes, and aromatic compounds such as phenol and cresol were detected in degradinite; and cutinite generated compounds similar to those found in dearadinite. We concluded that prist-1-ene and n-alkanes/n-alkenes were generated from wavy layers in the cutinite. The morphological changes observed after irradiation and the fact that the generated organic compounds changed with the maceral species indicated that the thermal effects of irradiation were restricted to the image area and that the pyrolysis reaction and thermal evaporation of the organic molecules in the macerals were limited as well. (C) 2003 Elsevier B.V. All rights reserved.