Insight into the reactivity of aromatic-rich fractions co-carbonized with polyethylene glycol for preparation of isotropic pitch with superior spinnability

Co-carbonization of aromatic-rich distillate oil (HCTO-RF) with polyethylene glycol (PEG) is a reliable process to prepare isotropic pitch with superior spinnability for producing carbon fibers. In the study, HCTO-RF was fractioned into light fraction, middle fraction, and heavy fraction. The chemical structural features of each fraction and their co-carbonization routes with PEG under the same reaction conditions were characterized and investigated. The results reveal that the light fraction was mainly composed of molecules containing one and two aromatic hexagonal rings with numerous longer alkyl side chains. The middle fraction was rich in less polycondensed two and three aromatic hexagonal ring compounds, which contained a certain number of naphthenic structures. The heavy fraction was mainly composed of four aromatic hexagonal ring compounds with higher condensation degrees and less short alkyl side chains. The co-carbonization reaction of PEG and the three fractions proceed by the routes: the radicals produced from the homolysis of the C-O and C-C bonds of PEG molecules; the activation of the aromatic units triggered by abstracting hydrogen; the polycondensation of activated aromatic units. The heavy fraction exhibited the most availability for co-carbonization reaction, followed by the middle fraction and the light fraction the worst.