Saturate Acts as Both a “Lubricant” and an “Activator” during the Conversion Process of Mesophase in Fluid Catalytic Cracking Slurry Oil

Saturate (Sa), the lightest component in fluid catalytic cracking (FCC) slurry oil, exhibits a poorly understood influence on the formation and development of mesophase, thereby constraining the production of premium-quality mesophase pitch. To address this issue, Sa is isolated from FCC slurry oil, and its concentration is modulated to investigate its impact on the formation and development of mesophase. The results indicate that Sa contains a high concentration of long alkane side chains and naphthenic structures, which render it an effective "lubricant" and "activator" within the reaction system. The addition of a small amount of Sa (≤5 wt %) maintains a low viscosity state of the reaction system, further facilitating the migration of aromatic molecules and promoting mesophase formation. It is crucial to note that excessive amounts of Sa (>10 wt %) significantly reduce the aromaticity and reactivity of the reaction system, further delaying the formation of mesophase. The reaction system exhibits moderate aromaticity and reactivity with low viscosity at 10 wt % Sa, leading to the formation of mesophase pitch with a moderate softening point (270 °C) and a wide-area optical texture (anisotropy length >60 μm, width >10 μm) within a short time of 6 h. This work establishes a robust theoretical foundation for producing premium-quality mesophase pitch through the regulation of raw material components.