Chemical transformations during pyrolysis of Rundle oil shale

Rundle shale (Queensland, Australia) was pyrolysed at 12.5 K min⁻¹ to 350–500 °C for 10–240 min. The structures of the liquid products and pyrolysis residues were investigated by a number of n.m.r. spectroscopic techniques including cross-polarization and dipolar dephasing. N.m.r. provided a simple method for detecting nitrile carbon and measuring terminal and internal olefinic hydrogen in shale oil. It was found that the ratio of terminal olefinic hydrogen to internal olefinic hydrogen in shale oil increases by a factor of three over the range 350–500 °C. Moreover, the results suggest that aromatic rings in Rundle shale residues are not highly substituted and hence that aromatic ring condensation reactions are not important during pyrolysis. From elemental, yield and n.m.r. data, the conversion of aliphatic carbon to aromatic carbon during pyrolysis was found to be as high as 25% at 500 °C.