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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Cracking (chemistry) | 3/3 | https://en.wikipedia.org/wiki/Cracking_(chemistry) | reference | science, encyclopedia | 2026-05-05T10:46:56.249729+00:00 | kb-cron |
==== Hydrocracking ==== Hydrocracking is a catalytic cracking process assisted by the presence of added hydrogen gas. Unlike a hydrotreater, hydrocracking uses hydrogen to break C–C bonds (hydrotreatment is conducted prior to hydrocracking to protect the catalysts in a hydrocracking process). In 2010, 265 million tonnes (261,000,000 long tons; 292,000,000 short tons) of petroleum was processed with this technology. The main feedstock is vacuum gas oil, a heavy fraction of petroleum. The products of this process are saturated hydrocarbons; depending on the reaction conditions (temperature, pressure, catalyst activity) these products range from ethane and LPG to heavier hydrocarbons consisting mostly of isoparaffins. Hydrocracking is normally facilitated by a bifunctional catalyst that is capable of rearranging and breaking hydrocarbon chains as well as adding hydrogen to aromatics and olefins to produce naphthenes and alkanes. The major products from hydrocracking are jet fuel and diesel, but low sulphur naphtha fractions and LPG are also produced. All these products have a very low content of sulfur and other contaminants with a goal of reducing the gasoil and naphtha range material to 10 PPM sulfur or lower. It is very common in Europe and Asia because those regions have high demand for diesel and kerosene. In the US, fluid catalytic cracking is more common because the demand for gasoline is higher. The hydrocracking process depends on the nature of the feedstock and the relative rates of the two competing reactions, hydrogenation and cracking. Heavy aromatic feedstock is converted into lighter products under a wide range of very high pressures (6,900–13,800 kilopascals (1,000–2,000 psi)) and fairly high temperatures (399–816 °C; 750–1,500 °F), in the presence of hydrogen and special catalysts. Indicative Isocracking (UOP VGO Hydrocracking) Yields Feedstock: Russian VGO 18.5 API, 2.28% Sulfur by wt, 0.28% Nitrogen by wt, Wax 6.5% by wt. Feedstock Distillation Curve
Products from a UOP Hydrocracker
Hydrocracking is (mostly) a licensed technology due to its complexity. Typically the licensor is also the catalyst provider. Also, unit internals can often be patented by the process licensors and are designed to support specific functions of the catalyst load. Currently, the major process licensors for hydrocracking are:
UOP Axens Chevron Lummus Global Topsoe Shell Criterion Elessent (formerly DuPont) ExxonMobil (iso-dewaxing for lubricant hydrocracking)
== Fundamentals == Outside of the industrial sector, cracking of C−C and C−H bonds are rare chemical reactions. In principle, ethane can undergo homolysis:
CH3CH3 → 2 CH3⋅ Because C−C bond energy is so high (377 kJ/mol), this reaction is not observed under laboratory conditions. More common examples of cracking reactions involve retro-Diels–Alder reactions. Illustrative is the thermal cracking of dicyclopentadiene to produce cyclopentadiene.
== See also == Steam reforming Catalytic reforming
== References ==
== External links == Information on cracking in oil refining from howstuffworks.com www.shukhov.org/shukhov.html — Vladimir Grigorievich Shukhov biography Colorado School of Mines - faculty member John Jechura is one of the best teachers of refining technology in the world, he puts his course materials online free of charge including a good presentation on hydrotreating/hydrocracking.