![]() The sequence consumes at least 12 molecules of hydrogen and includes three saturation reactions, two dealkylation reactions and at least three ring-opening reactions. 10.16, where a molecule of butyl naphthalene is converted into ethane, octane and whatever happens to be produced by the hydrocracking of ethyl decalin. Hydrocracking reactions release less heat because they are the sum of two reactions – the endothermic breaking of C–C bonds and the exothermic hydrogenation of the resulting olefins.Ĭonsider the sequence of reactions in Fig. In contrast, the saturation of olefins releases 30–32 kcal/mol, the saturation of monoaromatics releases 14–16 kcal/mol, and HDS and HDN release 12–22 kcal/mol. Table 10.4 shows that hydrocracking reactions release from 5–12 kcal/mol of hydrogen consumed. Hydrocracking units are normally made of low-alloy steels with Type 347 cladding or weld overlay to avoid intergranular stress-corrosion cracking as well as avoid hydrogen attack.Fig 10.16. Hydrogenating any sulfur, nitrogen or oxygen compounds in the original feedstock into gaseous hydrogen sulfide, ammonia and water.Hydrogenating unsaturated hydrocarbons to obtain saturated hydrocarbons, usually referred to as paraffins or alkanes.Cracking of high-boiling hydrocarbons found in crude oil into lower-boiling hydrocarbons.Heavy aromatic feedstock is converted into lighter products under a wide range of very high pressures (1,000–2,000 psi) and fairly high temperatures (750–1,500 ☏, 400–815 ☌), in the presence of hydrogen and special catalysts.Ĭatalytic hydrocracking involves three primary chemical processes: The hydrocracking process depends on the nature of the feedstock and the relative rates of the two competing reactions. The cracking function is provided by the acid catalyst support and the hydrogenation function is provided by the metals. Hydrocracking catalysts consist of active metals on solid, acidic supports and have a dual function, specifically a cracking function and a hydrogenation function. The result is that the hydrocracking products are essentially free of sulfur and nitrogen impurities and consist mostly of paraffinic hydrocarbons. The process takes place in a hydrogen-rich atmosphere at elevated temperatures (500–800 ☏, 260–425 ☌) and pressures (35–200 bars).Īny sulfur and nitrogen present in the hydrocracking feedstock are, to a large extent, also hydrogenated and form gaseous hydrogen sulfide (H 2S) and ammonia (NH 3), which are subsequently removed. Hydrocracking is a catalytic chemical process used in petroleum refineries for converting the high-boiling hydrocarbons in petroleum to low-boiling products such as gasoline, kerosene, jet fuel and diesel oil. ![]()
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