The stepwise hydrocracking of heptane-soluble polar fraction (Po) and asphaltene (As) isolated from wandoan coal-derived residue was carried out over a presulfided Ni-Mo/Al2O3 catalyst at 375 °C to investigate their chemical structures. Five nonpolar samples (Po/NP, Po/Po/NP, As/NP, As/As/NP, As/Po/NP) were obtained from the hydrocracking products as shown in Fig. 1.
The nonpolar products (Po/NP, As/NP) from the first hydrocracking of Po and As had lower molecular weights than those (Po/Po/NP, As/As/NP, As/Po/NP) from the second hydrocracking of the recovered polar materials. Each nonpolar product was separated into seven compound-types by HPLC equipped with a semipreparative Bondapak-NH2 column. Fr.3 and Fr.6 were analyzed by field ionization mass spectrometry (FIMS). The same compound-type fractions were shown to con-sist of similar polycyclic hydroaromatic structures, although those from the second hydrocracking have more naphthenic rings which resulted in higher molecular weights.
