Characterization of coal tar and components identification by Raman spectroscopy

Raman spectrum of coal tar was measured by using 355 nm laser at ambient temperature. Simultaneously, Raman spectra of 15 components which each weighted more than 1% in coal tar were also simulated. The calculated results are in good agreement with the experimental ones and the vibrations of Raman spectra of coal tar are assigned. The results indicate that the most components of coal tar are mainly composed of six-membered ring type hydrocarbons with the characteristic bands at 1 660, 1 420 and 1 265 cm^-1, which are attributed to the C-C stretching vibrations. When the hydrocarbons connect each other in a resonant mode and chain-like structure, 1 420 cm^-1 band is demonstrated significantly. When the hydrocarbons are embedded by the five-member ring type hydrocarbons, the intensity of 1 265 and 1 660 cm^-1 band increases significantly. There is little effect on the spectra of the component molecule provided the five-membered ring type hydrocarbons, heteroatom groups and methyl are only connected at the edge of the component molecule.