Cocarbonization properties of three dewaxed FCC DOs were studied with a low sulfur crude vacuum residue (LSVR) as complements to obtain better quality needle coke. The needle coke lump produced by cocarbonization in the tube bomb was evaluated in terms of its coefficient of thermal expansion (CTE) and amount of bottom mosaic coke. All initial DOs formed very large amounts of bottom mosaic coke in the cocarbonized lumps, while their middle portions were of excellent needle coke. One of dewaxed

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... s produced an excellent quality coke without any bottom mosaic coke, whereas others produced a very little of the former and a significant amount of the latter. Dewaxing slightly increased the CTE values of cokes cocarbonized at 480℃, which was optimum for the blend of LSVR and original DOs. Higher carbonization temperature appeared favorable to obtain lower CTE of the carbonized dewaxed DOs. The analyses of light aromatic fractions in dewaxed DOs indicate that extent of alkyl substitution and its length are fairly different from each other, and that higher aromaticity of the fraction in both terms is favorable to eliminate bottom mosaic coke. The optimum carbonization temperature, which is influenced by the dewaxing, is also discussed in relation to the structure of carbonization feed.