Improved Cocarbonization Properties of a Petroleum Vacuum Residue by Catalytic Hydrotreatment Leading to Production of Needle Coke.

Catalytic hydrotreatment of a petroleum low sulfur vacuum residue (LSVR) was studied to improve its carbonization properties since the residue gave bottom mosaic texture in a lump needle coke when it was cocarbonized with a particular paraffinic fluid catalytic cracking decant oil (FCC-DO). A Ni-Mo/ Silica-Alumina catalyst designed for residual oils converted completely the asphaltene fraction in LSVR so as to be soluble in hexane at 400° under 15MPa H₂. Excellent needle coke without bottom mosaic texture was produced from the hydrotreated LSVR via cocarbonization with FCC-DO at 480°. Another catalyst for the heavy distillate left some amount of hexane insoluble asphaltene fraction, although it was certainly depolymerized. Such a hydrotreated LSVR produced still a little but distinct amount of mosaic texture. The cocarbonization at 490° provided a smaller value of CTE (coefficient of thermal expansion) to the lump coke than that at 480°. The hydrotreatment reduces the reactivity of VR, raising slightly the optimum cocarbonization temperature.