Preparation of mesophase carbon microbeads from fluidized catalytic cracking residue oil: The effect of active structures on their coalescence.

• The relationship between olefins and the coalescence of mesophase spheres was investigated. • During thermal polycondensation, the olefins contents of residual oil, HS and HI-TS decreased while that of TI increased. • The involvement of olefins caused sharp increase of the system viscosity. • The involvement of olefins caused the deformation of mesophase spheres. • Catalytic hydrotreatment can shield the deformation of mesophase spheres. Mesophase carbon microbeads (MCMBs) were synthesized by thermal polycondensation with fluidized catalytic cracking residue oil (FRO) as the feedstock. The evolution features of functional groups of the residual oils and the residual solid products from thermal polymerization were analyzed, and the effect of olefinic compounds on the coalescence between mesophase spheres was investigated in depth. The results showed that the olefin contents of residual oil, heptane-soluble, and heptane-insoluble/toluene-soluble decreased simultaneously as the reaction proceeded while that of toluene-insoluble increased, indicating that the olefins in the solvent phase could not only provide molecule sources for the development of carbonaceous mesophase but also directly assemble into the insoluble mesogens. More importantly, the involvement of olefins caused a sharp increase of the system viscosity, making it difficult for the mesophase spheres to completely coalesce into regular large ones after cohering, leading to the apparent deformation. In contrast, catalytic hydrotreatment can saturate olefinic species and enhance the hydrogen transfer ability of FRO to further avoid the induction effect of olefins, slow down the mesophase development, reduce the system viscosity, and consequently avoid the deformation of mesophase spheres. [ABSTRACT FROM AUTHOR]