Chemical and Physical Properties of Petroleum Pitch

Tow commercially available petroleum pitches (P-I and P-II) have been characterized through the combination of conventional physicochemical techniques used for pitch characterization, like elemental analysis, penetration, softening point, viscosity, FTIR spectroscopy, TLC-FID, and 1H NMR spectroscopy. Elemental analysis and FTIR spectroscopy were employed to characterize the chemical composition of pitches. It was found that the pitches are similar in the hydrocarbon content and the (H/C) atomic ratio. Higher oxygen content differentiated P-I pitch from P-II pitch. More carbon, hydrogen and sulfur and lesser nitrogen was the distinctive feature observed for all commercial petroleum pitches. The distribution of vanadium and nickel did not show any apparent similarities in pitch samples. The amount of vanadium was almost thrice of that of nickel. TLC-FID was applied for the rapid determination of saturates, aromatics, and polar compounds. It was found that the content of aromatics was considerably higher in all pitch materials (over than 50 wt.%). ¹H NMR analysis confirmed that P-II pitch exhibits higher degree of aromaticity compared to P-I pitch. The similarities found are a consequence of the similar chemical composition of the pitches (determined by FTIR and TLC-FID), as well as the similar process used for the manufacturing of petroleum pitches. However, the results deducted from the set of physical experiments demonstrated that the two selected pitches behaved differently through penetration, softening point, and viscosity tests. These observations can affect later their applications, i.e. in the area of carbon fiber preparation or in the road pavement.