Separation and analysis of six fractions in low temperature coal tar by column chromatography

Abstract

The low temperature coal tar (CT) is taken as the raw material, and the extraction and column chromatography are used for detailed and accurate characterization in this paper. The n-heptane soluble fraction (CT-HS) and insoluble fraction (CT-HI) were obtained by n-heptane Soxhlet extraction. The extraction rate of CT-HS reached 92.79% (mass), which indicated that there are few heavy compounds in it. Further, different solvents (methylbenzene, benzene, ethyl acetate, methylbenzene-ethanol) were used to elute CT-HS by chromatographic column to obtain five fractions (saturates, aromatics, heteroatoms, phenolics and resins, named CT-SA, CT-AR, CT-HE, CT-PH, CT-RE, respectively). The yields of CT-SA, CT-AR, CT-HE, CT-PH, CT-RE are 42.12%, 10.43%, 2.19%, 9.50% and 6.63% (mass), respectively. Gas chromatography-mass spectrometry analysis of eluting components show that alkanes are the main components in CT, followed by polycyclic aromatics, and the corresponding fractions are CT-SA and CT-AR, respectively. The relative content of aliphatics in CT-SA is 76.93%, and the relative content of aromatics in CT-AR is 75.05%. This separation technology effectively separates and enriches different components in CT, and the activation energy required for the pyrolysis process of a single eluting fraction is lower than that of CT, which is expected to provide an important reference for the separation, analysis and conversion of complex oil products such as coal-oil co-processing products, coal tar and other complex heavy carbon oil products.