Characterization of the residual carbon in retorted oil shale by solid-state 13C n.m.r.

Cross-polarization and magic-angle spinning suggest that the aromatic carbons in oil shales are largely inert to thermal processes and instead are responsible for the carbonaceous residue obtained during retorting. These results are based on ¹³C n.m.r. measurements of the organic carbon distribution of oil shales, before and after Fischer assaying, and for oil shales of different grades, geographic location, geologic ages and formations. The n.m.r. measurements suggest further that measurements of the organic carbon distribution of oil shales heated to various temperatures have practical relevance, and that this information can be of value in discriminating between unconverted kerogen and residual carbon in heated oil shales.