Infrared Spectrum and Principal Component Analysis of Heavy Tar Cut by Different Fractions from Tar-Rich Coal

The composition and content of heavy tar vary significantly depending on the pyrolysis conditions and separation methods. This study aimed to effectively identify the main components and content of heavy coal tar and provide a theoretical basis for its subsequent utilization. To achieve this, simulated distillation and infrared spectrum analysis of heavy coal tar were conducted with a focus on understanding the impact of simulated distillation on the composition and structure of tar. The results showed that the fraction content in the tar underwent significant changes after simulated distillation at different temperatures. Specifically, the content of light oil decreased from 4.3 to 0.1%, while the asphalt content increased from 77.6 to 90.6%. Infrared spectrum and peak fitting revealed that the distilled coal tars exhibited similar characteristic peaks in regions associated with hydroxyl, aliphatic hydrocarbon, oxygen-containing functional group, and aromatic hydrocarbon structure. Based on the infrared spectrum of heavy coal tar, principal component analysis was conducted on different fractions. When using two principal components, the cumulative value reached 96.93%. It was found that PC1 displayed strong peak signals around 749 and 687 cm–1, while PC2 exhibited strong peak signals near 2356 and 1143 cm–1.