Cocarbonization Properties of Solvent Deasphalted Oil from a Petroleum Vacuum Residue in Production of Needle Coke.

Solvent deasphaltene treatment was applied to a low sulfur petroleum vacuum residue (LSVR) to reduce or eliminate bottom mosaic coke which was formed in its cocarbonization with a paraffinic FCC-DO. The C₅, C₆and C₇straight paraffins rejected 9, 3 and 1% of the asphaltene fractions from its heavier portions, respectively, according to their solubilities, giving C₅, C₆and C₇-DAO. The lesser the asphaltene fraction in the deasphalted oils (DAO), the lesser was the amount of bottom mosaic coke formed their separate carbonization. The complete removal, however, was achieved only by the cocarbonization of C₅and C₆DAO and FCC-DO. C₇DAO still formed mosaic coke in its cocarbonization. From analyses of DAOs, it is suggested that the heaviest portion of the asphaltene causes the bottom mosaic coke. The CTE values of coke from DAOs and FCC-DO were certainly greater than that of coke from combination of original LSVR and FCC-DO under optimum conditions. A slightly higher carbonization temperature may become optimum for the combination of DAO and FCC-DO, providing stability in absence of the heaviest portion of the asphaltene.