Hydrocracking product specifications

Table 3.22 Yields and product specifications from hydrocracking a Texan vacuum residue using the H-Oil process...

Middle distillates (jet and diesel) from high-conversion hydrocrackers meet or exceed finished product specifications. The heavy naphtha, however, usually goes to a catalytic reformer for octane improvement. The fractionator bottoms from partial conversion units can be sent to an FCC unit, an olefins plant, or a lube plant. 

The selection of the catalysts is of prime importance and must be made according to the characteristics of the feed, the process scheme and the operating conditions and product specifications. One of the keys of catalyst design is the balance between the two association of different hydrotreating and hydrocracking catalysts. 

Throughout these studies, no product other than propane was observed. However, subsequent studies by Sinfelt et al. [249—251] using silica-supported Group VIII metals (Co, Ni, Cu, Ru, Os, Rh, Ir, Pd and Pt) have shown that, in addition to hydrogenation, hydrocracking to ethane and methane occurs with cobalt, nickel, ruthenium and osmium, but not with the other metals studied. From the metal surface areas determined by hydrogen and carbon monoxide chemisorption, the specific activities of... 

Most hydrocracking catalysts of commercial interest are dual functional in nature, consisting of both a hydrogenation-dehydrogenation component and an acidic support. The reactions catalyzed by the individual components are quite different. In specific catalysts, the relative strengths of the two components can be varied. The reactions occurring and the products formed depend critically upon the balance between these two components. 

With pending low-sulfur fuel specifications, hydrocracking efforts will be increased to break complex hydrocarbon compounds and expose embedded sulfur molecules. Notably hydrocracking significantly upgrades feeds to downstream processes and fuel products, especially diesel products. 

Depending upon the specific needs, conventional plants may be converted to hybrid plants to improve capacity and/or product quality. An example of a hybrid configuration is used by Shell to manufacture their XHVI. In this particular case, the plant couples a lube hydrocracker with a solvent dewaxing unit. There are several modifications or improvements of known technologies that can be used as a Mix and Match to Needs to upgrade existing plants. 

Figure 2.9 shows the species-specific evolution profiles for (a) paraffin (b) olefin and (c) alkyl aromatic volatile products for the PE-PtHZSM-5 sample heated in hydrogen. As expected, paraffins dominated the hydrocracking volatile product slate and olefin and alkyl aromatic yields were greatly reduced compared with results obtained when the same sample was heated in helium. The paraffin profile for the PE-PtHZSM-5 sample heated in hydrogen exhibited two maxima. Below 200°C, volatile product mixtures were composed entirely of paraffins. As the sample temperature increased, a wide range of... 

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