Improved characterization of coal tar distillation cuts (200–500 °C): 1. Preparative separation into hydrocarbons and polar aromatics and characterization of polycyclic aromatic hydrocarbons by capillary g.c.-m.s. of anthracene oil

Abstract

Quantitative characterization of distillation cuts of high and low temperature coal tars has been carried out in two parts, first a separation of the basic nitrogen polyaromatic compounds on acid-modified silica, and second a semi-preparative liquid chromatography on aminosilane delivering the polyaromatic hydrocarbons (PAH), the neutral nitrogen (N-PAH) and the hydroxylated polyaromatic compounds (H-PAH). From the mass balances thus obtained, the evolution of these classes of compounds can be seen, depending on both the boiling points of the distillation cut and on the carbonization temperature. As far as identification and quantitative determination of the compounds (in each class) are concerned, two mass spectrometric analyses were performed. First with low energy electron impact mass spectrometry, the sample corresponding to one class of compounds was characterized by its distribution in groups according to carbon numbers. Second, with high energy electron impact mass spectrometry coupled to capillary column gas chromatography, identification of the individual structures was obtained while their quantitative determination is made by an independent capillary column gas chromatography. As an example, the complete analysis of an anthracene oil was performed and the results concerning the polycyclic aromatic hydrocarbons fraction are described in this paper. The analysis of the nitrogen (basic and neutral) and the hydroxylated polycyclic aromatic fractions will be the subject of a later publication.