Gasoline Hydrotreatment

The chemical objectives of naphtha and gasoline hydrotreatment are essentially the removal of S and N, and up to whether possible, to saturate the monoaromatic rings. One collateral requirement has to do with achieving the objective with no octane losses. The chemistry of the HDN of nitrogen compounds, commonly found in gasoline, has been the subject of studies, some of which are considered in this section. 

For nonhydrotreated feed, the gasoline sulfur level is about 10% of the feed sulfur level. For hydrotreated feed, it is about 5%. For example, if the sulfur content of a nonhydrotreated feed is 1.0 r (10,000 ppm), the sulfur in FCC gasoline will be 1,000 ppm. Assuming 80% desulfurization, feed to the FCC unit will contain 0.2% (2000 ppm) sulfur, resulting in FCC gasoline containing 100 ppm sulfur. Sulfur compounds that survive the hydrotreater are in the heav fraction and tend to end up in the LCO, decanted oil, and coke. 

On sulfided metallic phases the hydrotreatment reactions also takes place. Noble metal catalysts usually include a zeolitic support. They are particularly used for fulfilling two different objectives, in the case of a gasoline oriented HCK their cracking and isomerization activity is the most important (increasing high octane and conversion yield). In a diesel HCK unit, the noble metal catalyst is mainly oriented to aromatic saturation and cetane improvement. However, in this latter case, also sulfided metal catalysts are used, especially NiW. 

Based on correlations, the naphthas from the shale oil hydrotreater can be readily upgraded to high-octane gasolines by catalytic reforming. The middle distillate fractions will require some additional hydrotreating... 

A flow diagram for a proposed shale oil refinery is shown in Figure 5. An FCC unit is used as the primary cracking process. This refinery produces high-octane gasoline and diesel fuel. Jet fuel also could be produced by severely hydrogenating a kerosene cut (10) from the whole-oil hydrotreater or by using a hydrocracker in place of the FCC. The... 

Antos, G.J., Solari, B., and Monque, R. Hydroprocessing to produce reformulated gasolines The ISAL(TM) process. Hydrotreatment and Hydrocracking of Oil Fractions, 1997,... 

The hydrotreated shale oil is fractionated by distillation methods into gasoline, jet, diesel, and 650°F bottoms (residua). The jet and diesel fuel boiling ranges were determined experimentally to meet flash point and freeze or pour point requirements. Some of the residua was recycled back to the hydrotreater to increase jet and diesel fuel yields. 

Description The optimum feed is the mid-fraction of FCC gasoline from 70°C-150°C. This material is fed to the GT-BTX PluS unit, which extracts the sulfur and aromatics from the hydrocarbon stream. The sulfur-plus aromatic components are processed in a conventional hydrotreater to convert the sulfur into hydrogen sulfide (H S). Because the portion of gasoline being hydrotreated is reduced in volume and free of olefins, hydrogen consumption and operating costs are greatly reduced. 

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