Page 201 - Synthetic Fuels Handbook

FUELS FROM OIL SHALE 187

TABLE 6.5 Major Compound Types in Shale Oil

Saturates Paraffins
Cycloparaffins
Olefins
Aromatics Benzenes
Indans
Tetralins
Naphthalenes
Biphenyls
Phenanthrenes
Chrysenes
Heteroatom systems Benzothiophenes
Dibenzothiophenes
Phenols
Carbazoles
Pyridines
Quinolines
Nitriles
Ketones
Pyrroles

hydrogen pressures, and hydrotreating conditions are slightly more severe than for comparable
boiling range petroleum stocks, because of the higher nitrogen content of shale oil.
Shale oil contains a large variety of hydrocarbon compounds (Table 6.5) but also has
high nitrogen content compared to a nitrogen content of 0.2 to 0.3 weight percent for a
typical petroleum. In addition, shale oil also has a high olefin and diolefin content. It is the
presence of these olefins and diolefins, in conjunction with high nitrogen content, which
gives shale oil the characteristic difficulty in refining (Table 6.6) and the tendency to form
insoluble sediment. Crude shale oil also contains appreciable amounts of arsenic, iron, and
nickel that interfere with refining.
Upgrading, or partial refining, to improve the properties of a crude shale oil maybe car-
ried out using different options. Hydrotreating is the option of choice to produce a stable
product that is comparable to benchmark crude oils (Table 6.7). In terms of refining and
catalyst activity, the nitrogen content of shale oil is a disadvantage. But, in terms of the use
of shale oil residua as a modifier for asphalt, where nitrogen species can enhance binding

TABLE 6.6 Challenges for Oil Shale Processing
Particulates Plugging on processing
Product quality
Arsenic content Toxicity
Catalyst poison
High pour point Oil not pipeline quality
Nitrogen content Catalyst poison
Contributes to instability
Toxicity
Diolefins Contributes to instability
Plugging on processing