A study of the carbonization of ethylene tar pitch and needle coke formation

Abstract

Carbonization of ethylene tar pitch (ETP) and its hydrogenated products was studied in a tube bomb to find the appropriate carbonization conditions for producing a good needle coke. At the relatively low temperature of 460 °C under a pressure of 784 kPa for 10 h, ETP produced lump coke of low CTE and of excellent flow texture without any mosaic coke being formed at the bottom of the reactor (bottom mosaic coke). A higher carbonization temperature (480 °C) gave a mosaic texture coke of large CTE, although the carbonization was complete in 6 h. A lower carbonization temperature (440 °C) or pressures above 784 kPa resulted in bottom mosaic coke. The catalytic hydrogenation of ETP improved the anisotropic texture of coke carbonization at 480 °C, but could not eliminate the mosaic coke forming at the reactor bottom. N.m.r. and g.p.c. analysis revealed that ETP contained some olefins and high molecular weight substances in the major 2–3 ring aromatic hydrocarbons. The roles of such minor components in the formation of needle and mosaic cokes are discussed.