Oleum

Last updated
Oleum
Oleum fuming.jpg
Identifiers
ECHA InfoCard 100.116.872 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 616-954-1
Properties
C9H8O3
Appearancecolorless fuming liquid
Related compounds
Related compounds
 sulfuric acid
sulfur trioxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Oleum (Latin oleum, meaning oil), or fuming sulfuric acid, is a term referring to solutions of various compositions of sulfur trioxide in sulfuric acid, or sometimes more specifically to disulfuric acid (also known as pyrosulfuric acid). [1]

Contents

Oleums can be described by the formula ySO3·H2O where y is the total molar mass of sulfur trioxide content. The value of y can be varied, to include different oleums. They can also be described by the formula H2SO4·xSO3 where x is now defined as the molar free sulfur trioxide content. Oleum is generally assessed according to the free SO3 content by mass. It can also be expressed as a percentage of sulfuric acid strength; for oleum concentrations, that would be over 100%. For example, 10% oleum can also be expressed as H2SO4·0.13611SO3, 1.13611SO3·H2O or 102.25% sulfuric acid. The conversion between % acid and % oleum is:

For x = 1 and y = 2 the empirical formula H2S2O7 for disulfuric (pyrosulfuric) acid is obtained. Pure disulfuric acid is a solid at room temperature, melting at 36 °C and rarely used either in the laboratory or industrial processes — although recent research indicates that pure disulfuric acid has never been isolated yet. [2]

Production

Oleum is produced in the contact process, where sulfur is oxidized to sulfur trioxide which is subsequently dissolved in concentrated sulfuric acid. [3] Sulfuric acid itself is regenerated by dilution of part of the oleum.

The lead chamber process for sulfuric acid production was abandoned, partly because it could not produce sulfur trioxide or concentrated sulfuric acid directly due to corrosion of the lead, and absorption of NO2 gas. Until this process was made obsolete by the contact process, oleum had to be obtained through indirect methods. Historically, the biggest production of oleum came from the distillation of iron sulfates at Nordhausen, from which the historical name Nordhausen sulfuric acid is derived. [1]

Applications

Sulfuric acid production

Oleum is an important intermediate in the manufacture of sulfuric acid due to its high enthalpy of hydration. When SO3 is added to water, rather than dissolving, it tends to form a fine mist of sulfuric acid, which is difficult to manage. However, SO3 added to concentrated sulfuric acid readily dissolves, forming oleum which can then be diluted with water to produce additional concentrated sulfuric acid. [4]

Typically, above concentrations of 98.3%, sulfuric acid will undergo a spontaneous decomposition into sulfur trioxide and water

H2SO4 ⇌ SO3 + H2O

This means that sulfuric acid above said concentration will readily degenerate until it reaches 98.3%; this is impractical in some applications such as synthesis where anhydrous conditions are preferred (like alcohol eliminations). The addition of sulfur trioxide allows the concentration to be increased by means of Le Chatelier's principle.

As an intermediate for transportation

Oleum is a useful form for transporting sulfuric acid compounds, typically in rail tank cars, between oil refineries (which produce various sulfur compounds as a byproduct of refining) and industrial consumers.

Certain compositions of oleum are solid at room temperature, and thus are safer to ship than as a liquid. Solid oleum can be converted into liquid at the destination by steam heating or dilution or concentration. This requires care to prevent overheating and evaporation of sulfur trioxide. To extract it from a tank car requires careful heating using steam conduits inside the tank car. Great care must be taken to avoid overheating, as this can increase the pressure in the tank car beyond the tank's safety valve limit.

In addition, oleum is less corrosive to metals than sulfuric acid, because there is no free water to attack surfaces. [5] Because of that, sulfuric acid is sometimes concentrated to oleum for in-plant pipelines and then diluted back to acid for use in industrial reactions.

In Richmond, California in 1993 a significant release occurred due to overheating, causing a release of sulfur trioxide [6] that absorbed moisture from the atmosphere, creating a mist of micrometre-sized sulfuric acid particles that formed an inhalation health hazard. [7] This mist spread over a wide area. [8]

Organic chemistry research

Oleum is a harsh reagent, and is highly corrosive. One important use of oleum as a reagent is the secondary nitration of nitrobenzene. The first nitration can occur with nitric acid in sulfuric acid, but this deactivates the ring towards further electrophilic substitution. A stronger reagent, oleum, is needed to introduce the second nitro group onto the aromatic ring.

Explosives manufacture

Oleum is used in the manufacture of many explosives with the notable exception of nitrocellulose. [9] (In modern manufacturing of nitrocellulose, the H2SO4 concentration is often adjusted using oleum.) The chemical requirements for explosives manufacture often require anhydrous mixtures containing nitric acid and sulfuric acid. Ordinary commercial grade nitric acid consists of the constant boiling azeotrope of nitric acid and water, and contains 68% nitric acid. Mixtures of ordinary nitric acid in sulfuric acid therefore contain substantial amounts of water and are unsuitable for processes such as those that occur in the manufacture of trinitrotoluene.

The synthesis of RDX and certain other explosives does not require oleum. [10]

Anhydrous nitric acid, referred to as white fuming nitric acid, can be used to prepare water-free nitration mixtures, and this method is used in laboratory scale operations where the cost of material is not of primary importance. Fuming nitric acid is hazardous to handle and transport, because it is extremely corrosive and volatile. For industrial use, such strong nitration mixtures are prepared by mixing oleum with ordinary commercial nitric acid so that the free sulfur trioxide in the oleum consumes the water in the nitric acid. [11]

Reactions

Like concentrated sulfuric acid, oleum is such a strong dehydrating agent that if poured onto powdered glucose, or virtually any other sugar, it will draw the hydrogen elements of water out of the sugar in an exothermic reaction, leaving a residue of nearly pure carbon as a solid. This carbon expands outward, hardening as a solid black substance with gas bubbles in it.[ citation needed ]

Related Research Articles

<span class="mw-page-title-main">Nitroglycerin</span> Chemical compound

Nitroglycerin (NG), also, known as trinitroglycerin (TNG), nitro, glyceryl trinitrate (GTN), or 1,2,3-trinitroxypropane, is a dense, colorless, oily, explosive liquid most commonly produced by nitrating glycerol with white fuming nitric acid under conditions appropriate to the formation of the nitric acid ester. Chemically, the substance is an organic nitrate compound rather than a nitro compound, but the traditional name is retained. Discovered in 1847 by Ascanio Sobrero, nitroglycerin has been used as an active ingredient in the manufacture of explosives, namely dynamite, and as such it is employed in the construction, demolition, and mining industries. It is combined with nitrocellulose to form double-based smokeless powder, which has been used as a propellant in artillery and firearms since the 1880s.

Nitric acid is the inorganic compound with the formula HNO3. It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into oxides of nitrogen. Most commercially available nitric acid has a concentration of 68% in water. When the solution contains more than 86% HNO3, it is referred to as fuming nitric acid. Depending on the amount of nitrogen dioxide present, fuming nitric acid is further characterized as red fuming nitric acid at concentrations above 86%, or white fuming nitric acid at concentrations above 95%.

<span class="mw-page-title-main">Sulfuric acid</span> Chemical compound (H₂SO₄)

Sulfuric acid or sulphuric acid, known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, and hydrogen, with the molecular formula H2SO4. It is a colorless, odorless, and viscous liquid that is miscible with water.

Chromic acid is an inorganic acid composed of the elements chromium, oxygen, and hydrogen. It is a dark, purplish red, odorless, sand-like solid powder. When dissolved in water, it is a strong acid. There are 2 types of chromic acid: molecular chromic acid with the formula H
2CrO
4 and dichromic acid with the formula H
2Cr
2O
7.

<span class="mw-page-title-main">Nitrous acid</span> Chemical compound

Nitrous acid is a weak and monoprotic acid known only in solution, in the gas phase and in the form of nitrite salts. Nitrous acid is used to make diazonium salts from amines. The resulting diazonium salts are reagents in azo coupling reactions to give azo dyes.

Sulfur trioxide (alternative spelling sulphur trioxide, also known as nisso sulfan) is the chemical compound with the formula SO3. It has been described as "unquestionably the most important economically" sulfur oxide. It is prepared on an industrial scale as a precursor to sulfuric acid.

In chemistry, a superacid (according to the original definition) is an acid with an acidity greater than that of 100% pure sulfuric acid (H2SO4), which has a Hammett acidity function (H0) of −12. According to the modern definition, a superacid is a medium in which the chemical potential of the proton is higher than in pure sulfuric acid. Commercially available superacids include trifluoromethanesulfonic acid (CF3SO3H), also known as triflic acid, and fluorosulfuric acid (HSO3F), both of which are about a thousand times stronger (i.e. have more negative H0 values) than sulfuric acid. Most strong superacids are prepared by the combination of a strong Lewis acid and a strong Brønsted acid. A strong superacid of this kind is fluoroantimonic acid. Another group of superacids, the carborane acid group, contains some of the strongest known acids. Finally, when treated with anhydrous acid, zeolites (microporous aluminosilicate minerals) will contain superacidic sites within their pores. These materials are used on massive scale by the petrochemical industry in the upgrading of hydrocarbons to make fuels.

The contact process is the current method of producing sulfuric acid in the high concentrations needed for industrial processes. Platinum was originally used as the catalyst for this reaction; however, as it is susceptible to reacting with arsenic impurities in the sulfur feedstock, vanadium(V) oxide (V2O5) is now preferred.

<span class="mw-page-title-main">Sulfamic acid</span> Chemical compound

Sulfamic acid, also known as amidosulfonic acid, amidosulfuric acid, aminosulfonic acid, sulphamic acid and sulfamidic acid, is a molecular compound with the formula H3NSO3. This colourless, water-soluble compound finds many applications. Sulfamic acid melts at 205 °C before decomposing at higher temperatures to water, sulfur trioxide, sulfur dioxide and nitrogen.

<span class="mw-page-title-main">Disulfuric acid</span> Chemical compound

Disulfuric acid (alternative spelling disulphuric acid) or pyrosulfuric acid (alternative spelling pyrosulphuric acid), also named oleum, is a sulfur oxoacid. It is a major constituent of fuming sulfuric acid, oleum, and this is how most chemists encounter it. As confirmed by X-ray crystallography, the molecule consists of a pair of SO2(OH) groups joined by an oxide.

<span class="mw-page-title-main">Fluorosulfuric acid</span> Chemical compound

Fluorosulfuric acid (IUPAC name: sulfurofluoridic acid) is the inorganic compound with the chemical formula HSO3F. It is one of the strongest acids commercially available. It is a tetrahedral molecule and is closely related to sulfuric acid, H2SO4, substituting a fluorine atom for one of the hydroxyl groups. It is a colourless liquid, although commercial samples are often yellow.

<span class="mw-page-title-main">Potassium bisulfate</span> Chemical compound

Potassium bisulfate/ Potassium bisulphate is an inorganic compound with the chemical formula KHSO4 and is the potassium acid salt of sulfuric acid. It is a white, water-soluble solid.

<span class="mw-page-title-main">Chromyl chloride</span> Chemical compound

Chromyl chloride is an inorganic compound with the formula CrO2Cl2. It is a reddish brown compound that is a volatile liquid at room temperature, which is unusual for transition metal compounds.

The chemical element nitrogen is one of the most abundant elements in the universe and can form many compounds. It can take several oxidation states; but the most common oxidation states are -3 and +3. Nitrogen can form nitride and nitrate ions. It also forms a part of nitric acid and nitrate salts. Nitrogen compounds also have an important role in organic chemistry, as nitrogen is part of proteins, amino acids and adenosine triphosphate.

<span class="mw-page-title-main">Palladium(II) nitrate</span> Chemical compound

Palladium(II) nitrate is the inorganic compound with the formula Pd(NO3)2.(H2O)x where x = 0 or 2. The anhydrous and dihydrate are deliquescent solids. According to X-ray crystallography, both compounds feature square planar Pd(II) with unidentate nitrate ligands. The anhydrous compound, which is a coordination polymer, is yellow.

<span class="mw-page-title-main">Ammonium dinitramide</span> Chemical compound

Ammonium dinitramide (ADN) is the ammonium salt of dinitraminic acid. ADN decomposes under heat to leave only nitrogen, oxygen, and water. The ions are the ammonium ion NH4+ and the dinitramide N(NO2)2−.

The wet sulfuric acid process (WSA process) is a gas desulfurization process. After Danish company Haldor Topsoe introduced this technology in 1987, it has been recognized as a process for recovering sulfur from various process gases in the form of commercial quality sulfuric acid (H2SO4) with the simultaneous production of high-pressure steam. The WSA process can be applied in all industries where sulfur removal presents an issue.

<span class="mw-page-title-main">Antimony(III) sulfate</span> Chemical compound

Antimony sulfate, Sb2(SO4)3, is a hygroscopic salt formed by reacting antimony or its compounds with hot sulfuric acid. It is used in doping of semiconductors and in the production of explosives and fireworks.

Gold(III) sulfide or auric sulfide is an inorganic compound with the formula Au2S3. Auric sulfide has been described as a black and amorphous solid. Only the amorphous phase has been produced, and the only evidence of existence is based on thermal analysis.

References

  1. 1 2 Hinds, John Iredelle Dillard (January 1902). Inorganic Chemistry: With the Elements of Physical and Theoretical Chemistry. J. Wiley & sons.
  2. ↑ Kim, Seong Kyu; Lee, Han Myoung; Kim, Kwang S. (28 October 2015). "Disulfuric acid dissociated by two water molecules: ab initio and density functional theory calculations". Physical Chemistry Chemical Physics. 17 (43): 28556–28564. Bibcode:2015PCCP...1728556K. doi:10.1039/C5CP05201G. PMID   26400266.
  3. ↑ Speight, James G. (2017-01-01), Speight, James G. (ed.), "Chapter Three - Industrial Inorganic Chemistry", Environmental Inorganic Chemistry for Engineers, Butterworth-Heinemann, pp. 111–169, ISBN   978-0-12-849891-0 , retrieved 2021-10-26
  4. ↑ Considine, Douglas M. (1974). Chemical and Process Technology Encyclopedia. McGraw-Hill. pp. 1070–1.
  5. ↑ "Storage Tanks". Sulphuric Acid on the Web. DKL Engineering.
  6. ↑ "Major Accidents at Chemical/Refinery Plants in Contra Costa County". Contra Costa Health Services.
  7. ↑ Baskett, R.L.; Vogt, P.J.; Schalk, W.W. III; Pobanz, B.M. (February 3, 1994). ARAC dispersion modeling of the July 26, 1993 oleum tank car spill in Richmond, California (Report). Office of Scientific and Technical Information (OSTI). doi:10.2172/10137425.
  8. ↑ "CASE STUDY – Richmond, California Oleum Release". EPIcode. Archived from the original on 2013-08-28.{{cite web}}: CS1 maint: unfit URL (link)
  9. ↑ Urbanski, Tadeusz (1965). Chemistry and Technology of Explosives. Vol. 2. Oxford: Pergamon Press. p. 329.
  10. ↑ "Preparation of 1,3,5-trinitro-1,3,5-triazine (RDX, Cyclonit, Hexogen)". PreChem.
  11. ↑ Urbanski, Vol 1, pp 347–349
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.