Mesophase pitches prepared from methylnaphthalene by the aid of HF BF₃

Mesophase pitches were prepared from methylnaphthalenes using HF BF₃ as a catalyst to improve their spinning and stabilization properties in comparison with those from naphthalene. Methylnaphthalene-derived mesophase pitch carried a number of methyl groups in addition to naphthenic groups which were introduced by nondehydrogenative polymerization reaction of naphthalene rings. Many methyl groups in methylnaphthalene were left in the mesophase pitch to be very effective for lowering the softening point and improving the spinnability and stabilization reactivity, stabilization being achieved within 10 minutes at 270°C. It was found that the methyl group migrated between 1-and 2-positions on the naphthalene ring in the presence of super strong acid of HF BF₃, giving the same structure and properties of mesophase pitches regardless of its positions in the starting materials. Effects of the methyl group on the reactivity and structural changes of the stabilization were discussed based on the infrared (IR) spectra.