High severity hydrotreating

Feedstock Characterization. The feedstocks studied in this effort were a Wilmington vacuum gas oil and two hydrotreated products of this gas oil. The specific samples considered were sample No. 1693, an untreated Wilmington vacuum gas oil, a low severity hydrotreated product from sample No. 1693 (sample No. WM-2-2R, hydrotreated at 375° C, 1.5 LHSV, and 1500 psig), and a high severity hydrotreated product (sample No. WM-2-9, hydrotreated at 425° C, 0.5 LHSV, 1500 psig). The available physical properties for each of these feedstocks are given in Table I. 

Hydrocracking40-44 is a highly severe hydrotreating operation and a highly flexible and versatile process. It allows the manufacture of products with wide composition range by selecting appropriate feed, catalyst, and operating conditions. Since... 

Figure 4. Flow diagram refining of SRC-II oil by high severity hydrotreating, case 1...

REFINING SRC-II OIL BY HIGH SEVERITY HYDROTREATING TO PRODUCE 50,000 BARRELS PER CALENDAR DAY OF MOTOR GASOLINE PLUS JET FUEL DOE CONTRACT EF-76-C-01-2315 ... 

Feeds and Products, Barrels per Calendar Day Refinery Input High Severity Hydrotreating Catalytic Reforming Hydrogen Manufacture Recovery and Sulfur Plant Refinery Fuel Motor Gasoline Kerosene Jet Fuel By- Products... 

Figure 2. Simplified flow diagram refining of H-coal syncrude by high severity hydrotreating...

This is consistent with the easy-sulflir/hindered-sulfur h othesis, which predicts that nearly all of the sulfur left behind after high-severity hydrotreating is encased in hindered compoimds. These compounds contain multiple aromatic rings, so they more likely (relative to other sulfur compounds) to be incorporated into the coke that forms on FCC catalysts. When the coke is burned away, the sulfur is converted into sulfur oxides (SOx), which ends up in the regenerator flue gas. 

Performance Analysis. In order to determine the effect of hydrotreating on catalytic cracking performance, the above feedstocks were evaluated at a low severity cracking condition (catalyst-to-oil ratio of 6.0 and reactor temperature of 910° F) and a high severity cracking condition (catalyst-to-oil of 8.0 and reactor temperature of 1010° F). The results from the catalytic cracking of these feedstocks (shown in Tables I and II) are shown in Tables III through V. The results presented in these tables are... 

Table Xb. - Analysis of liquid product fractions from high severity cracking of mildly hydrotreated Wilmington vacuum gas oil (No. WM-2-2R)...

Figure 8. Distribution of sulfur in high severity cracking products as a function of hydrotreating pretreatment.

Figure 14. Effects of hydrotreating severity on catalytic cracking light gas composition — high severity cracking.

In Case 3A, fluid catalytic cracking is evaluated. To eliminate all net products heavier than gasoline, it was necessary to use high severity initial hydrotreating to obtain high enough conversion in the catalytic cracker. 

Supercritical Hydrotreatment of SCE Shale Oil. SCE shale oil was hydrotreated at high severity because of its high nitrogen content (Table i) and extremely high viscosity. The experimental results are shown in Table III. Based on the shale oil fed, the product distribution is the following 12 gases, 52 boiling less than 300°F (calculated by difference) and 36 in the heavy... 

A severe hydrotreating plant will have a flow scheme similar to the hydrofinishing unit shown in Fig. 1.11. Hydrocracking is a highly exothermic reaction, so cold hydrogen must be injected at several points in the catalyst bed to moderate the temperature rise. Operating conditions are severe, with pressures of 100-180 bar and reaction temperatures of 350 20°C. 

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