Abstract

Neutral heterocompounds are one of the major fractions of the pyrolysis or hydrogenation products of brown coals. They are classified into two groups by chromatographic methods. The first group (thiophenes, aliphatic ketones) elutes from the normal phase with non-polar eluents, in analogy with aromatic hydrocarbons. They can be separated from aromatic hydrocarbons by complex formation with palladium chloride [ Fuel, 65 (1986) 270-273; J. Chromatogr., 509 (1990) 27–32]. The second group elutes from the normal phase with polar eluents. The neutral heterocompounds in an extract of heat-pretreated brown coal were separated by semipreparative high-performance liquid chromatography. They were fractionated by increasing polarity and subsequently characterized by Fourier transform infrared spectrometry, protonnuclear magnetic resonance and mass spectrometry. Results to these spectrometric methods ( i.e. the existence of hydroxy and carbonyl residues) could be verified by derivatization with 2,4-dinitrophenylhydrazine and 3,5-dinitrobenzoylchloride followed by qualification of these derivatives by reversed-phase chromatography. The neutral heterocompounds were hydrogenated in two steps, and the resulting hydrocarbons were characterized by semipreparative and analytical high-performance liquid chromatography, as well as by capillary gas chromatography. General conclusions about the structures, as result of the combination of the different applied methods, could be made.

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