Effect of Thermal Treatment on Asphaltene: Conversion Composition and Microstructure Analysis

The primary objective of the work presented in this chapter was to investigate and quantify how asphaltene molecules change under thermal stress. Nitrogen-protected pyrolysis of the pitch product of solvent deasphalting (SDA) was carried out in an open tube furnace, and the asphaltene samples were extracted from SDA and its thermal cracking residues based on their solubility properties. The asphaltene samples were characterized to further understand the changes that take place in asphaltenes during thermal cracking. With an increase in the operating temperature or reaction time, the asphaltene content of the thermally cracked residue experienced an increasing trend followed by a steady decline that was accompanied by a gradual increase in the yield of the insoluble toluene. The atomic mole ratio n(H)/n(C) decreased significantly from approximately 1.0569 to 0.6618. A comparison between asphaltenes from thermal treatment and SDA was conducted using infrared data analysis to distinguish the aromaticity changes. On the other hand, the aromaticity index (IAr = I3047/(I3047+I2918)) increased from the 0.021 to 0.097 with a slight decrease of intensity ratio in the CH2/CH3 of the asphaltene molecules, which indicates that thermal treatment promotes the aromaticity of asphaltene. This conclusion was further proved by the weak growth of the D/G ratio (height) during Raman analysis. In addition, the surface of the asphaltene was successfully characterized as a function of the agglomerate particles, numerous porous structures, and smooth surfaces using scanning electron microscopic imaging.