Upgrading
Although raw shale oil can be immediately burnt as a fuel oil, many of its applications require that it be upgraded. The differing properties of the raw oils call for correspondingly various pre-treatments before it can be sent to a conventional oil refinery.
Particulates in the raw oil clog downstream processes; sulfur and nitrogen create air pollution. Sulfur and nitrogen, along with the arsenic and iron that may be present, also destroy the catalysts used in refining. Olefins form insoluble sediments and cause instability. The oxygen within the oil, present at higher levels than in crude oil, lends itself to the formation of destructive free radicals. Hydrodesulfurization and hydrodenitrogenation can address these problems and result in a product comparable to benchmark crude oil. Phenols can be first be removed by water extraction. Upgrading shale oil into transport fuels requires adjusting hydrogen–carbon ratios by adding hydrogen (hydrocracking) or removing carbon (coking).
Shale oil produced by some technologies, such as the Kiviter process, can be used without further upgrading as an oil constituent and as a phenolic compound. Distillate oils from the Kiviter process can also be used as diluents for petroleum-originated heavy oils and as an adhesive-enhancing additive in bituminous materials such as asphalt.
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