Role of quinoline insoluble particles during the processing of coal tars to produce graphene materials

Abstract

This work studies the utilization of a binder grade industrial tar with an inherent content in primary quinolone insoluble particles (QIs) and the correspondent free-QI tar obtained from it by a sedimentation process as raw sources of graphene materials via different preparation procedures. Graphene oxides (GOs) were prepared via the oxidation of binder tar-based graphite and subsequent sonication. The presence of QIs contributes to decreasing both the yield of the oxidation and of the exfoliation steps. This is due to the greater reactivity of QI particles towards oxidation, which modifies the distribution of the oxygen functional groups in the oxidized graphite, impeding its exfoliation. Also, as a consequence of the higher crystallinity of parent graphite without QIs, larger GO sheets were obtained in that case. On the other hand, the presence of QIs in the parent graphite facilitates its solvent exfoliation behavior in N-methyl-pyrrolidinone (NMP) to yield few layer graphene (FLG), but contributes to a decrease in the size of the flakes of the graphene materials obtained.