Composition analysis of coal tar—fractionation

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Due to the highly complex composition of coal tar, there are estimated to be tens of thousands of organic compound components, of which about 500 have been identified so far. But most components are present in small amounts or trace amounts. There are only 12 components in coal tar whose concentration exceeds 1%, such as naphthalene, methylnaphthalene, oxofluorene, acenaphthene, anthracene, phenanthrene, carbazole, fluoranthene, pyrene, and cresol (including its three isomers). This poses great difficulties for the analysis of tar. In accordance with the national standard (GB515-88) for the determination of the distillation range of petroleum products, the tar obtained from coal carbonization is distilled, and the tar is divided into the following five fractions based on boiling point: 1. Light oil (up to 360°C). Gas chromatography is used for quantitative analysis of the four fractions with boiling points below 360°C; qualitative identification of the main components in coal tar is carried out using reference samples, while quantitative analysis is performed via area normalization. Of course, high-performance liquid chromatography is also available nowadays for analyzing tar, but the tar needs to be pre-treated, and its accuracy is limited.