Recycle hydrocracking, extinction

In this paper we compare behavior of catalysts in extinction recycle hydrocracking. In such a processing scheme, all of the feed is ultimately converted to product boiling below a certain predefined temperature. The reaction paths of individual feed components may differ from catalyst to catalyst. Product distributions and properties are examined to determine the general effects of changes in catalytic properties. 

The properties of the 650° F+ fraction of the hydrotreated shale oil also indicate that it will be an appropriate feed to an extinction recycle hydrocracker in situations where jet fuel is a desired product. Supporting pilot plant studies are described elsewhere (1,2,3). 

HCO is the sidecut stream from the main column that boils between LCO and decanted oil (DO). HCO is often used as a pumparound stream to transfer heat to the fresh feed and/or to the debutanizer reboiier. HCO is recycled to extinction, withdrawn as a product and processed in a hydrocracker, or blended with the decant oil. 

Figure 5. Reactor temperature and specific gravity of the recycle feed as a function of time-on-stream for recycle-to-extinction and single-pass modes of hydrocracking using NiW/RE-X catalyst. (Reproduced from reference 45, Copyright 1983 American Chemical Society.)...

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