Preparation of carbon fibre precursors from the pyrolysis and copyrolysis of Avgamasya asphaltite and Göynük oil shale: vacuum distillation and hexane extraction

Göynük oil shale (GOS) and Avgamasya asphaltite (AA) mixed in various ratios were used as raw materials for pitch precursors. Pure GOS and AA and their mixtures were pyrolysed at 550 °C and the resultant tars were vacuum distilled at 300 °C and 3 Torr for 60 min to produce pitch precursors. The pitch obtained in the highest yield was further modified by extraction with hexane. Structural characterisation by FTIR and ¹H and ¹³C NMR, and elemental analysis of the vacuum distillation pitches and the vacuum-distilled hexane-extracted pitch showed that vacuum distillation did not increase the softening point and toluene-insoluble (TI) content of the pitches. Further extraction with hexane removed significant amounts of aliphatic components from the pitch and increased the softening point to 136 °C. The vacuum-distilled, hexane-extracted pitch showed good spinnability into fibres of 15-20 μm diameter. The as-spun fibres were stabilised by nitric acid. The green fibres were pre-treated with air at low temperatures in order to complete stabilisation before the carbonisation process at 1000 °C. SEM images of the carbonised fibres showed surface defects due to pitch composition and/or insufficient stabilisation.