Preparation of carbon fiber from heavy oil residue through bromination

A pitch precursor for a general purpose carbon fiber was prepared by condensation of pyrolized fuel oil (petroleum residual oil) with bromine under nitrogen blowing. Such a condensation raised the softening point of the pitch from 40°C to 265°C with a yield of 43%. The pitch precursor showed an enhanced aromaticity and enlarged molecular size, which led to a reduction in molecular mobility and optical isotropy. The precursor was spun into fibers of 20 μm diameter at a take-up speed of 700 m/min. The fiber was stepwise stabilized in air and carbonized in Ar gas to obtain an isotropic carbon fiber. The carbon fiber exhibited tensile strengths of 500–800 MPa though the fiber was formed via a crude method. The electric conductivity of the carbon fiber was relatively high, 2.2×10² S/cm, sufficient to be used as electrode materials.