Cocarbonization Properties of Heat-Treated Petroleum Vacuum Residue with FCC Decant Oils in Production of Needle Coke.

Pyrolytic modification of asphaltene fraction in a low sulfur vacuum residue(LSVR) was studied to eliminate the bottom mosaic coke formation in cocarbonization with a predominantly paraffinic FCCDO. Highly restrictive conditions for pyrolytic modification of LSVR, at 420℃C for 1-5h, were found to be effective to eliminate bottom mosaic coke in the cocarbonization at 460℃C. Pyrolytic modification, at higher of lower temperature caused formation of the bottom mosaic. The analyses of heat treated LSVR suggested that the heat treatment depolymerized the asphaltene and improved its aromaticity, while producing closely limited amounts of benzene insoluble(BI) or mesophase. Such a modified LSVR may obtain thermal stability and solubility in blending with FCC-DO, to control cocarbonization, preventing phase separation at early stage of mesophase, eliminating reactive asphaltene fraction to form bottom mosaic texture.