Hydrodenitrogenation (HDN) is an industrial process for the removal of

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

from

petroleum Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring un ...

. Organonitrogen compounds, even though they occur at low levels, are undesirable because they cause poisoning of downstream catalysts. Furthermore, upon combustion, organonitrogen compounds generate

NOx In atmospheric chemistry, is shorthand for nitric oxide () and nitrogen dioxide (), the nitrogen oxides that are most relevant for air pollution. These gases contribute to the formation of smog and acid rain, as well as affecting tro ...

, a pollutant. HDN is effected as general

hydroprocessing Hydroprocessing is a catalytic term relating to the processes of hydrocracking and hydrotreating. These process are for the removal of sulfur, oxygen, nitrogen and metals from crude oil, this is done in the refining of fuel A fuel is any ma ...

, which traditionally focuses on

hydrodesulfurization Hydrodesulfurization (HDS), also called hydrotreatment or hydrotreating, is a catalytic chemical process widely used to desulfurization, remove sulfur (S) from natural gas and from oil refinery, refined petroleum products, such as gasoline, g ...

(HDS) because sulfur compounds are even more problematic. To some extent,

hydrodeoxygenation Hydrodeoxygenation (HDO) is a hydrogenolysis process for removing oxygen from oxygen-containing compounds. Typical HDO catalysts commonly are sulfided nickel-molybdenum or cobalt-molybdenum on gamma alumina. An idealized reaction is: :R2O + 2 H2 ...

(HDO) is also effected. Typical organonitrogen compounds in petroleum include

quinoline Quinoline is a heterocyclic aromatic organic compound with the chemical formula C9H7N. It is a colorless hygroscopic liquid with a strong odor. Aged samples, especially if exposed to light, become yellow and later brown. Quinoline is only sl ...

s and

porphyrin Porphyrins ( ) are heterocyclic, macrocyclic, organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges (). In vertebrates, an essential member of the porphyrin group is heme, w ...

s and their derivatives. The total nitrogen content is typically less than 1% and the targeted levels are in the ppm range. As described in

organic geochemistry Organic geochemistry is the study of the impacts and processes that organisms have had on the Earth. It is mainly concerned with the composition and mode of origin of organic matter in rocks and in bodies of water. The study of organic geochemistr ...

, organonitrogen compounds are derivatives or degradation products of the compounds in the living matter that comprised the precursor to fossil fuels. In HDN, the organonitrogen compounds are treated at high temperatures with

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

in the presence of a

catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

, the net transformation being: :R₃N + 3 H₂ → 3 RH + NH₃ The catalysts generally consist of

cobalt Cobalt is a chemical element; it has Symbol (chemistry), symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. ...

and

nickel Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...

as well as

molybdenum disulfide Molybdenum disulfide (or moly) is an inorganic chemistry, inorganic compound composed of molybdenum and sulfur. Its chemical formula is . The compound is classified as a transition metal dichalcogenide. It is a silvery black solid that occurs as ...

or less often tungsten disulfide supported on

alumina Aluminium oxide (or aluminium(III) oxide) is a chemical compound of aluminium and oxygen with the chemical formula . It is the most commonly occurring of several aluminium oxides, and specifically identified as aluminium oxide. It is commonly ...

. The precise composition of the catalyst, i.e. Co/Ni and Mo/W ratios, are tuned for particular feedstocks. A wide variety of catalyst compositions have been considered, including metal

phosphide In chemistry, a phosphide is a compound containing the ion or its equivalent. Many different phosphides are known, with widely differing structures. Most commonly encountered on the binary phosphides, i.e. those materials consisting only of pho ...

s.Oyama, S. Ted; Gott, Travis; Zhao, Haiyan; Lee, Yong-Kul "Transition metal phosphide hydroprocessing catalysts: A review" Catalysis Today 2009, vol. 143, pp. 94-107 {{doi, 10.1016/j.cattod.2008.09.019

References

Oil refining Chemical processes Natural gas technology