Pyrolysis and hydropyrolysis of coal asphaltenes and preasphaltenes -relationships between reactivity and structural parameters derived from chemical and spectroscopic analyses

Four asphaltene and preasphaltene pairs derived from successive stages in the British Coal donor solvent extraction process have been catalytically hydrogenated (at 450 °C and ˜ 8.7 MPa) to determine the relative ease with which they underwent subsequent reaction to oils and other products. An attempt has been made to correlate the observed reactivity differences with a comprehensive characterization of their structures, using elemental analysis, phenolic oxygen content, molecular weight determinations and ¹H and ¹³C n.m.r. spectroscopy. For the four asphaltenes, the heteroatom contents (O, N and S) decreased with the extent of hydrogenation: for oxygen this was due to a decrease in the phenolic oxygen content, the non-phenolic oxygen content remaining constant. Decreased reactivity correlated well with increasing carbon content, and with increased condensation (as measured by n.m.r. analysis). For the four preasphaltenes, trends in the heteroatom contents were similar, although not completely uniform (particularly for N): the yield structures after hydrogenation were alike for all four, and this was mirrored in the ¹H and ¹³C n.m.r. data which revealed no differences among them in terms of hydrogen or carbon type distribution. © 1989.