Identification by 13C NMR of carbon types in shale oil and their relationship to pyrolysis conditions

A number of samples of shale oil prepared under various conditions have been examined by 13C NMR using multiple-pulse techniques that allow carbon-type assignments. Previous assignments by Netzel et al (1981) are confirmed and several new ones made. Product chemistry is then examined as a function of heating conditions. New or verified observations are: (1) isoprenoids are evolved in the early stages of oil generation, and the average length of normal hydrocarbons in the evolved oil is approximately independent of the extent of kerogen conversion, (2) alkene content depends strongly on the heating rate during pyrolysis but average normal chain length does not, and (3) the ratio of isoprenoid to normal carbons and the average normal chain length in bitumen are greater than in shale oil, but there are greater questions about the correct equation for calculating the average normal chain length of bitumen.