Composition and Structural Characteristics of Heavy Distillate from Xinjiang High Temperature Coal Tar

Abstract

Heavy distillate (HD) derived from the high temperature coal tar was extracted in parallel with carbon disulfide (CDS) and isometric carbon disulfide/acetone mixture (IMCDSAM) to obtain extracts 1 and 2 (E₁ and E₂) and extraction residues 1 and 2 (R₁ and R₂), respectively. R₁ was extracted again with IMCDSAM to obtain extract 3 (E₃) and extraction residue 3 (R₃). The extracts and extraction residues were analyzed by Fourier transform infrared spectrometry (FTIR), gas chromatography/mass (GC/MS) spectrometry and Orbitrap mass spectrometry (Orbitrap MS) to obtain the composition, structural characteristics, and distribution of organic matters in the samples. The condensation degree of E₁ is high, indicating that E₁ contains more aromatic compounds, and the absorption peak intensity of >C=O in E₂ is significance demonstration, indicating that oxygen-containing compounds in E₂ mainly exist in the form of ketones, acids, and esters. E₃ contains more heteroatom-containing organic compounds rather than aromatic. Relative abundances of ON compounds in E₁, E₂, and E₃ had a significance advantage, indicating ON compounds is the main component in HD, and O₁N_x-O₆N_x compounds were further analyzed. R₁, R₂, and R₃ were analyzed by FTIR, thermogravimetric (TG), N2 adsorption-desorption and scanning electron microscopy (SEM). There is an obvious absorption peak of aromatic-nitrile (-C≡N) in R₁, and the difference from functional group distribution and mass loss of R₂ and R₃ is subtle which can be related to the similar structure after completely extracted by IMCDSAM. R₂ and R₃ show a higher specific surface area than R₁. The surface morphology of R₁ is more shaggy which may an important reason cause large mass loss of it.

Keywords: High temperature coal tar, Heavy distillate, extraction, Residues