Structure and stabilization reactivity of mesophase pitch derived from f c c-decant oils

Abstract

Structure and stabilization reactivities of three mesophase pitches (MP-1-3) derived from fluid catalytic cracking (f c c)-decant oils were compared to reveal the structure-reactivity correlation in the stabilization reaction, which is the slowest step of the pitch-based carbon fibre production. Analyses of the toluene soluble fraction in mesophase pitches using ¹H-, ¹³C-nuclear magnetic resonance (NMR), infrared and FD-mass spectroscopy suggested that the most abundant molecules in MP-2 and MP-3, which should have the highest and lowest softening points, respectively, consisted of a 7-ring aromatic skeleton with two phenyl groups, molecular weight 478 and a 10-ring aromatic skeleton with a phenyl and four methyl groups, molecular weight 556, respectively. MP-3 exhibited much more rapid stabilization and oxygen up take than MP-2. The analysis of stabilized fibre with Fourier transform-infrared spectroscopy indicated that the oxidative stabilization consisted of the following three steps: (1) oxygen up take to produce functional groups such as carbonyl, phenolic and ether groups; (2) growth of the aromatic ring; and (3) molecular association through hydrogen bonding. The first step of oxidation occurred at substituent alkyl, naphthenic and isolated aromatic hydrogens in the mesogen molecules regardless of the mesophase pitches. The reactivity of the mesophase pitch appears to be correlated to the number of such groups present.