The disruption of aromatic stacking order in mesophase petroleum coke via reductive alkylation

Abstract

The thermolysis of a 510° C vacuum residuum of petroleum under hydrogen can lead to an insoluble coke material of correlation length in the direction of aromatic stacking (L c) of 7.3 nm, which is more than 3 times greater than that typically found for coals of anthracite rank. In spite of this high degree of stacking order, the coke material can be solubilized via the technique of reductive alkylation. The coke is combined with tetrahydrofuran and potassium metal, and the aromatic “molecules” of the coke form solubilized anions (K° consumption 5–6 mmol/gram). These anions react with alkyl iodides to form alkylated aromatic adducts, of vapor pressure osmometry molecular weight ca. 1000 gram/mole and showing only weak intermolecular paraffin interactions in X-ray diffraction. Thus, a high degree of aromatic stacking, as manifested by a narrow (002) peak in diffraction, does not imply that the material is refractory; the chemical significance of such aromatic-aromatic interactions is currently of interest to those studying both carbon fibers and coal conversion. Heteronuclear correlated 1H/1b 13C NMR is used to elucidate the detailed chemistry of the disruption of aromatic stacking.