Process for producing pitch for using as raw material for carbon fibers

Claim 1

A process for producing a pitch used as a raw material for producing carbon fibers, which comprises the steps of: (A) catalytically cracking a hydrogenated residual oil having a sulfur content of 0.7% by weight or less, a vanadium content of 10.0 ppm or less, a nickel content of 5.0 ppm or less and an asphaltene content of 1.0% by weight or less, said hydrogenated residual oil being produced by subjecting a petroleum heavy residual oil to hydrogenation treatment in the presence of a hydrogenation catalyst at a temperature of 370° to 450° C., a pressure of 70 to 210 kg/cm 2 G, a liquid space velocity of 0.4 to 2.0 per hour and a ratio of hydrogen/oil of 700 to 1,700 Nm/Kl, or catalytically cracking a mixture of said hydrogenated residual oil and a hydrogenated distillate oil having a sulfur content of 0.4% by weight or less, said hydrogenated distillate oil being produced by processing a petroleum heavy residual oil by reduced pressure distillation to prepare a reduced pressure distillate oil having 95% or more of a distillate fraction having a boiling point of 300° to 550° C. at atmospheric pressure, and subjecting the resulting distillate oil to hydrogenation in the presence of a hydrogenation catalyst at a temperature of 300° to 410° C., a pressure of 40 to 150 kg/cm 2 G, a liquid space velocity of 0.5 to 3.0 per hour and a ratio of hydrogen/oil of 260 to 1,700 Nm 3 /Kl, said catalytic cracking being carried out using a catalytic cracking catalyst at a temperature of 470° to 540° C., a pressure of 0.5 to 5.0 kg/cm 2 G, and a ratio of catalyst:oil of 5:1 to 15:1 (by weight); (B) distilling the resulting cracking oil to produce a high boiling point fraction having a boiling point of 300° C. or more; and (C) thermally modifying the resulting fraction at a temperature of 390° to 430° C. and a heating time of 1 to 30 hours.