ABSTRACT
Heteroatoms, particularly nitrogen, sulfur, and trace metals (Tables 6.1, 6.2, and 6.3), are present in petroleum and might also be expected to be present in liquid fuels and other products from petroleum. Indeed, this is often the case, although there may have been some skeletal changes induced by the refining process(es). Oxygen is much more difficult to define in petroleum and liquid fuels.
