Disadvantages of hydrocracking1/4/2023 Reaction conditions in the hydrocracking process are very drastic with pressures of 80 - 200 bar and temperatures in the range of 270 - 450 ☌. Hydrocracking does not generate any alkenes because hydrogen reacts with the generated radicals forming alkanes with low boiling points instead. In this process, catalytic cracking is carried out in an atmosphere of hydrogen (300 - 500 m 3 hydrogen per ton of hydrocarbon) with the advantage that impurities, such as sulfur and nitrogen, can be removed from the product easily as hydrogen sulfide and ammonia, respectively. As a hydrogen-addition process, hydrocracking provides high yields of valuable distillates without producing low-grade byproducts (e.g., heavy oils, gas, or coke) as experienced in carbon rejection processes such as coking.For technical reasons, hydrocracking was only made possible in the late Fifties of the last century. With hydrocracking it is possible to convert an aromatic compound to a paraffinic compounds without any loss of carbon, as shown in Figure 7.10. One should note that that the aromatic rings cannot be cracked before they are saturated with hydrogen. The hydrocracking process has two dimensions: Hydrogenation of aromatic rings and cracking of aliphatic compounds, as shown in Figure 7.10, using naphthalene as an example for an aromatic ring system. The principal objective of hydrocracking is to decrease the molecular weight and boiling point of heavy oils to produce saturated hydrocarbons (diesel and jet fuel) from highly aromatic feedstocks (e.g., LCO from FCC) and distillation residua. The advantages of hydrocracking include its ability to handle a wide range of feedstocks that may be difficult to process by catalytic cracking and its flexibility in selectivity between light and middle distillates. The interest in hydrocracking has been attributed to the increasing demand for light and middle distillates, the availability of byproduct hydrogen in large quantities from catalytic reforming, and the environmental regulations limiting sulfur and aromatic hydrocarbons in motor fuels. Catalytic hydrocracking is one of the latest additions to petroleum refining processes, with the first modern commercial unit started up by Chevron in 1958.
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