Hydrodesulfurization
Hydrodesulfurization , HDS for short , also hydrofinishing , hydrofining , hydrotreating , is the desulfurization of mineral oil products through hydrogenation (reaction of sulfur compounds with hydrogen ). The process is of considerable importance in the petroleum industry. Components for the production of gas oils ( diesel fuel , EL heating oil ) are hydrogenated, but intermediate products ( naphtha ) for further processing ( catalytic reforming , isomerization ) are also treated in order to protect sensitive catalysts from sulfur contamination, for example the noble metal catalysts platinum or rhenium which are poisoned by very low sulfur concentrations . In addition to sulfur compounds, olefins , nitrogen and oxygen compounds are hydrogenated during this process .
history
Although some reactions involving the catalytic hydrogenation of organic substances were already known, the property of finely divided nickel to catalyze the fixation of hydrogen to hydrocarbon double bonds was not discovered until 1897 by the French chemist Paul Sabatier . His work showed that unsaturated hydrocarbons in the vapor phase can be converted into saturated ones with the aid of hydrogen and a catalytic metal . This was the basis for the modern catalytic hydrogenation process.
Soon after, the German chemist Wilhelm Normann showed that catalytic hydrogenation could be used for the hydrogenation of unsaturated fatty acids or glycerides in the liquid phase. He was awarded a patent in 1902 in Germany and 1903 in Britain. This was the beginning of what is now a global industry.
In the mid-1950s, the first precious metal catalytic reforming process , known as the platformer process, was commercialized . At the same time, the catalytic hydrodesulfurization of naphtha feed for reformers was commercialized. Today almost all oil refineries worldwide have one or more HDS units.
application
Due to the strict environmental protection regulations nowadays almost all important mineral fuels consist of hydrogenated components.
The motor gasoline specification of 10 mg / kg sulfur can be achieved by hydrogenating all components. This low value is necessary to protect the sulfur-sensitive platinum-doped vehicle catalyst.
A significant proportion of the kerosene is hydrogenated. However, this is not done to remove the sulfur (Jet A1 may have a sulfur content of 3000 mg / kg), but to hydrogenate other harmful compounds ( naphthenic acids , measured using the so-called Total Acid Number = TAN).
The production of diesel fuel with 10 mg / kg sulfur requires the hydrogenation of all components ( kerosene , gas oils ). In the engine, the sulfur content burns to SO 2 or SO 3 . The finest SO 3 droplets represent condensation nuclei for carbon particles, so high sulfur concentrations lead to increased soot formation.
Heating oil EL will soon have a sulfur content of <50 mg / kg and thus also consist only of hydrogenated components.
In some refineries with a Cat Cracker ( FCC ) system, the vacuum gas oil is hydrogenated to reduce the sulfur content of the finished FCC products.
In the manufacture of medical white oils and petroleum jelly from base oils from petroleum processing, hydrodesulfurization is used in industry.
process
Depending on the requirements, naphtha, kerosene and gas oils of various origins can be used as input products in the process. As catalysts are nickel - molybdenum or cobalt -molybdenum catalysts. The liquid feed is preheated (together with hydrogen-rich gas) by means of a heat exchanger , brought to the required reaction temperature of approx. 320 to 360 ° C in an oven and then fed into the reactor. At the reactor inlet, the feed is then - depending on the conditions - gaseous (naphtha, kerosene) or is in the 2-phase state (gaseous / liquid, e.g. gas oils). At pressures of 20 to 80 bar, depending on the design of the plant and the specific feedstock, the mixture reacts on the catalyst (if the feed is in a 2-phase state, the system catalyst-gaseous hydrocarbons -liquid hydrocarbons is called the trickle phase System). The hydrogenation reaction taking place on the catalyst (see picture) ultimately leads to H 2 S and the hydrogenated hydrocarbon residue. The sulfur- reduced product, unused hydrogen and small amounts of light hydrocarbons (C1-C4) and hydrogen sulfide formed by cracking are located in the reactor outlet .
In a first stage, the mixture is cooled and a hydrogen-rich gas is recycled back into use (so-called recycle gas). Sometimes there is a (high pressure) amine wash in the recycle to remove the H 2 S from the recycle stream (increase of the hydrogen partial pressure). In a next step, the product mixture is stripped to remove the H 2 S and the light constituents . The stripped gas (H 2 S, C1-C4) is freed from H 2 S in what is known as an amine scrubber and used as refinery fuel gas. The H 2 S bound to the amine is released from the solution in a regenerator (“stripping column” for amine solution) and moved to the so-called Claus plant . There it is converted into pure sulfur . The sulfur from desulfurization plants now makes a significant contribution to global sulfur production. The finished product of the HDS plant is low-sulfur naphtha, kerosene, gas oil or vacuum gas oil .
literature
- Hydrodesulfurization and Hydrodenitrogenation (Hardcover) by Toshiaki Kabe, Atsushi Ishihara, Weihua Qian, Verlag Wiley-VCH (2000), ISBN 978-3-527-30116-4 .
- L. Harwell, S. Thakkar, S. Polcar, RE Palmer, PH Desai: Study outlines optimum ULSD hydrotreater design . In: Oil & Gas Journal . tape 101 , no. 29 , July 28, 2003, p. 50-56 ( online ).
- Sunggyu Lee (Ed.): Encyclopedia of Chemical Processing (Print) . Taylor & Francis, New York 2005, ISBN 978-0-8247-5563-8 , pp. 1289 ( limited preview in Google Book Search).
- James G. Speight (Ed.): The Desulfurization of Heavy Oils and Residua . 2nd Edition. M. Dekker-Verlag, New York 1999, ISBN 978-0-203-90992-8 , pp. 226 ( limited preview in Google Book search).
Individual evidence
- ^ Paul Sabatier, J.-B. Senderens: Action du nickel sur l'éthylène. Synthèse de l'éthane . In: Comptes rendus hebdomadaires des séances de l'Académie des sciences . tape 124 , 1897, pp. 1358–1361 (French, digitized in Gallica ).
- ^ Paul Sabatier, J.-B. Senderens: Hydrogenations directes réalisées en présence de nickel réduit: preparation de l'hexahydrobenzène . In: Comptes rendus hebdomadaires des séances de l'Académie des sciences . tape 132 , 1901, pp. 210–212 (French, digitized in Gallica ).
- ^ Armand Lattes: De l'hydrogénation catalytique à la théorie chimique de la catalyse: Paul Sabatier, chimiste de génie, apôtre de la decentralization . In: Comptes rendus de l'Académie des sciences - Series IIC - Chemistry . tape 3 , no. 9 , 2000, pp. 705-709 , doi : 10.1016 / S1387-1609 (00) 01184-1 .
- ↑ DE Patent DE141029 (Espacenet, record not available)
- ↑ Patent GB190301515 : Process for Converting Unsaturated Fatty Acids or their Glycerides into Saturated Compounds. Published on November 26th, 1903 , inventor: Wilhelm Normann.