Methyl tert-butyl ether

Last updated
Methyl tert-butyl ether
MTBE-2D.svg
Methyl tert-butyl ether 3D ball.png
Names
Preferred IUPAC name
2-Methoxy-2-methylpropane
Other names
  • Methyl tertiary-butyl ether
  • Methyl t-butyl ether
  • MTBE
  • tert-Butyl methyl ether
  • tBME
  • tert-BuOMe
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.015.140 OOjs UI icon edit-ltr-progressive.svg
KEGG
PubChem CID
UNII
  • InChI=1S/C5H12O/c1-5(2,3)6-4/h1-4H3 Yes check.svgY
    Key: BZLVMXJERCGZMT-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C5H12O/c1-5(2,3)6-4/h1-4H3
    Key: BZLVMXJERCGZMT-UHFFFAOYAA
  • O(C(C)(C)C)C
Properties
C5H12O
Molar mass 88.150 g·mol−1
Appearancecolourless liquid
Density 0.7404 g/cm3
Melting point −108.6 °C (−163.5 °F; 164.6 K)
Boiling point 55.5 °C (131.9 °F; 328.6 K)
26 g/L (20 °C) [1]
Vapor pressure 27kPa (20ºC)
Viscosity 3.4·10-4 Pa·s (at 25ºC)
Hazards
NFPA 704 (fire diamond)
NFPA 704.svgHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
3
0
Flash point −32.78 °C (−27.00 °F; 240.37 K)
435 °C (815 °F; 708 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

Methyl tert-butyl ether (MTBE), also known as tert-butyl methyl ether, is an organic compound with a structural formula (CH3)3COCH3. MTBE is a volatile, flammable, and colorless liquid that is sparingly soluble in water. [1] Primarily used as a fuel additive, MTBE is blended into gasoline to increase its octane rating and knock resistance, and reduce unwanted emissions. [2] [3]

Contents

Production and properties

MTBE is manufactured via the chemical reaction of methanol and isobutylene. Methanol is primarily derived from natural gas, [4] where steam reforming converts the various light hydrocarbons in natural gas (primarily methane) into carbon monoxide and hydrogen. [5] The resulting gases then further react in the presence of a catalyst to form methanol. [6] Isobutylene can be produced through a variety of methods. n-butane can be isomerized into isobutane which can be dehydrogenated to isobutylene. [7] In the Halcon process, t-Butyl hydroperoxide derived from isobutane oxygenation is reacted with propylene to produce propylene oxide and t-butanol. The t-butanol can be dehydrated to isobutylene.

MTBE production in the U.S. peaked in 1999 at 260,000 barrels per day [8] before dropping down to about 50,000 barrels per day and holding steady, [9] mostly for the export market. After the purchase of SABIC, [10] [11] oil giant Saudi Aramco is now considered to be the world's largest producer [12] with an estimated production capacity of 2.37 million metric tons per year (mt/yr). [13] Worldwide production capacity of MTBE in 2018 was estimated to be 35 million metric tons. [14]

Uses

MTBE is used as a fuel component in fuel for gasoline engines. It is one of a group of chemicals commonly known as oxygenates because they raise the oxygen content of gasoline.

As anti-knocking agent

In the U.S. MTBE has been used in gasoline at low levels since 1979, replacing tetraethyllead (TEL) as an antiknock (octane rating) additive to prevent engine knocking. [15] Oxygenates also help gasoline burn more completely, reducing tailpipe emissions. Oxygenates also dilute or displace gasoline components such as aromatics (e.g., benzene). Before the introduction of other oxygenates and octane enhancers, refiners chose MTBE for its blending characteristics and low cost.

Alternatives to MTBE as an anti-knock agent

Other oxygenates are available as additives for gasoline including ethanol and other ethers such as ETBE.

Ethanol has been advertised as a safe alternative by agricultural and other interest groups in the U.S. and Europe. In 2003, California was the first U.S. state to start replacing MTBE with ethanol.

An alternative to ethanol is ETBE, which is manufactured from ethanol and isobutene. Its performance as an additive is similar to MTBE, but due to the higher price of ethanol compared to methanol, it is more expensive.

Higher quality gasoline is also an alternative, so that additives such as MTBE are unnecessary. Iso-octane itself is used. MTBE plants can be retrofitted to produce iso-octane from isobutylene. [16] [17]

As a solvent

MTBE is used in industry as a safer alternative to diethyl ether (which is commonly used in academic research) as the tert-butyl group prevents MTBE from forming potentially explosive peroxides. It also is used as a solvent in academic research, [18] [19] [20] although it is used less commonly than diethyl ether. Although an ether, MTBE is a poor Lewis base and does not support formation of Grignard reagents. It is also unstable toward strong acids. It reacts dangerously with bromine. [21]

MTBE forms azeotropes with water (52.6 °C; 96.5% MTBE) [22] and methanol (51.3 °C; 68.6% MTBE). [23]

In a medical procedure called contact dissolution therapy, MTBE is injected directly into the gallbladder to dissolve gallstones. [24] [25]

MTBE is used in organic chemistry as a relatively inexpensive solvent with properties comparable to diethyl ether, but with a higher boiling point and less solubility in water. As a solvent, MTBE has one distinct advantage over most ethers - it has a much lower tendency to form explosive organic peroxides. It is widely used as a solvent in industry where, for safety and regulatory reasons, handling diethyl ether or other ethers is much more difficult and expensive. MTBE as a solvent is used in the oil refining industry as a method for dewaxing waxy petroleum fractions.

Persistence and pervasiveness in the environment

MTBE gives water an unpleasant taste at very low concentrations. MTBE often is introduced into water-supply aquifers by leaking underground storage tanks (USTs) at gasoline stations or by gasoline containing MTBE being spilled onto the ground. The higher water solubility and persistence of MTBE cause it to travel faster and farther than many other components of gasoline when released into an aquifer. [26]

MTBE is biodegraded by the action of bacteria. In the proper type of bioreactor, such as a fluidized bed bioreactor, MTBE may be removed rapidly and economically from water to undetectable levels. Activated carbon produced from coconut shells and optimized for MTBE adsorption may reduce MTBE to undetectable levels, [27] although this level of reduction is likely to occur only in the most ideal circumstances. There are currently no known published cases of any in-situ treatment method that has been capable of reducing contaminant concentrations to baseline (pre-development) conditions within the aquifer soil matrix.

According to the International Agency for Research on Cancer (IARC), a cancer research agency of the World Health Organization, MTBE is not classified as a human carcinogen. MTBE may be tasted in water at concentrations of 5–15 µg/L (5-15ppb). [28]

As of 2007, researchers have limited data about the health effects of ingestion of MTBE. The United States Environmental Protection Agency (EPA) has concluded that available data are inadequate to quantify health risks of MTBE at low exposure levels in drinking water, but the data support the conclusion that MTBE is a potential human carcinogen at high doses. [29]

Regulation and litigation in the U.S.

Restrictions on MTBE manufacturing and use

In 2000, EPA drafted plans to phase out the use of MTBE nationwide over four years.[ citation needed ] Some states enacted MTBE prohibitions without waiting for federal restrictions. California banned MTBE as a gasoline additive in 2002. [30] The State of New York banned the use of MTBE as a "fuel additive", effective in 2004. [31] However, MTBE is still legal in the state for other industrial uses. [32]

The Energy Policy Act of 2005, as approved by the U.S. House of Representatives, did not include a provision for shielding MTBE manufacturers from water contamination lawsuits. This provision was first proposed in 2003 and had been thought by some to be a priority of Tom DeLay and Rep. Joe Barton, then chairman of the Energy and Commerce Committee. [33] This bill did include a provision that gave MTBE makers, including some major oil companies, $2 billion in transition assistance while MTBE was phased out over the following nine years. [34] Due to opposition in the Senate, [35] the conference report dropped all MTBE provisions. The final bill was signed into law by President George W. Bush. [36] The lack of MTBE liability protection is resulting in a switchover to the use of ethanol as a gasoline additive.

Cleanup costs and litigation

MTBE removal from groundwater and soil contamination in the U.S. was estimated to cost from $1 billion [37] to US$30 billion, [38] including removing the compound from aquifers and municipal water supplies and replacing leaky underground oil tanks. In one case, the cost to oil companies to clean up the MTBE in wells belonging to the city of Santa Monica, California was estimated to exceed $200 million. [39] In another case, New York City estimated a $250 million cost for cleanup of a single wellfield in the borough of Queens in 2009. [40] In 2013 a jury awarded the State of New Hampshire $236 million in damages in order to treat groundwater contaminated by MTBE. [41]

Many lawsuits are still pending regarding MTBE contamination of public and private drinking water supplies.

Drinking water regulations

EPA first listed MTBE in 1998 as a candidate for development of a national Maximum Contaminant Level (MCL) standard in drinking water. [42] As of 2020 the agency has not announced whether it will develop an MCL. [43] EPA uses toxicity data in developing MCLs for public water systems. [44]

California established a state-level MCL for MTBE, 13 micrograms per liter, in 2000. [45]

See also

Related Research Articles

<span class="mw-page-title-main">Alcohol (chemistry)</span> Organic compound with at least one hydroxyl (–OH) group

In chemistry, an alcohol is a type of organic compound that carries at least one hydroxyl functional group bound to a saturated carbon atom. Alcohols range from the simple, like methanol and ethanol, to complex, like sugar alcohols and cholesterol. The presence of an OH group strongly modifies the properties of hydrocarbons, conferring hydrophilic (water-loving) properties. The OH group provides a site at which many reactions can occur.

<span class="mw-page-title-main">Ether</span> Organic compounds made of alkyl/aryl groups bound to oxygen (R–O–R)

In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two organyl groups. They have the general formula R−O−R′, where R and R′ represent organyl groups. Ethers can again be classified into two varieties: if the organyl groups are the same on both sides of the oxygen atom, then it is a simple or symmetrical ether, whereas if they are different, the ethers are called mixed or unsymmetrical ethers. A typical example of the first group is the solvent and anaesthetic diethyl ether, commonly referred to simply as "ether". Ethers are common in organic chemistry and even more prevalent in biochemistry, as they are common linkages in carbohydrates and lignin.

<span class="mw-page-title-main">Methanol</span> CH3OH; simplest possible alcohol

Methanol is an organic chemical compound and the simplest aliphatic alcohol, with the chemical formula CH3OH. It is a light, volatile, colorless and flammable liquid with a distinctive alcoholic odour similar to that of ethanol . Methanol acquired the name wood alcohol because it was once produced chiefly by the destructive distillation of wood. Today, methanol is mainly produced industrially by hydrogenation of carbon monoxide.

Butanol (also called butyl alcohol) is a four-carbon alcohol with a formula of C4H9OH, which occurs in five isomeric structures (four structural isomers), from a straight-chain primary alcohol to a branched-chain tertiary alcohol; all are a butyl or isobutyl group linked to a hydroxyl group (sometimes represented as BuOH, 1-BuOH, i-BuOH, and t-BuOH). These are 1-butanol, two stereoisomers of sec-butyl alcohol, isobutanol and tert-butyl alcohol. Butanol is primarily used as a solvent and as an intermediate in chemical synthesis, and may be used as a fuel. Biologically produced butanol is called biobutanol, which may be n-butanol or isobutanol.

<span class="mw-page-title-main">Petrochemical</span> Chemical product derived from petroleum

Petrochemicals are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable sources such as maize, palm fruit or sugar cane.

<span class="mw-page-title-main">Biofuel</span> Type of biological fuel

Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels such as oil. Biofuel can be produced from plants or from agricultural, domestic or industrial biowaste. Biofuels are mostly used for transportation, but can also be used for heating and electricity. Biofuels are regarded as a renewable energy source. The use of biofuel has been subject to criticism regarding the "food vs fuel" debate, varied assessments of their sustainability, and possible deforestation and biodiversity loss as a result of biofuel production.

Ethyl <i>tert</i>-butyl ether Oxygenate gasoline additive in the production of gasoline from crude oil

Ethyl tertiary-butyl ether (ETBE), also known as ethyl tert-butyl ether, is commonly used as an oxygenate gasoline additive in the production of gasoline from crude oil. ETBE offers equal or greater air quality benefits than ethanol, while being technically and logistically less challenging. Unlike ethanol, ETBE does not induce evaporation of gasoline, which is one of the causes of smog, and does not absorb moisture from the atmosphere.

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

Diisopropyl ether is a secondary ether that is used as a solvent. It is a colorless liquid that is slightly soluble in water, but miscible with organic solvents. It is used as an extractant and an oxygenate gasoline additive. It is obtained industrially as a byproduct in the production of isopropanol by hydration of propylene. Diisopropyl ether is sometimes represented by the abbreviation DIPE.

<span class="mw-page-title-main">Isobutylene</span> Unsaturated hydrocarbon compound (H2C=C(CH3)2)

Isobutylene is a hydrocarbon with the chemical formula (CH3)2C=CH2. It is a four-carbon branched alkene (olefin), one of the four isomers of butylene. It is a colorless flammable gas, and is of considerable industrial value.

<i>tert</i>-Butyl alcohol Chemical compound

tert-Butyl alcohol is the simplest tertiary alcohol, with a formula of (CH3)3COH (sometimes represented as t-BuOH). Its isomers are 1-butanol, isobutanol, and butan-2-ol. tert-Butyl alcohol is a colorless solid, which melts near room temperature and has a camphor-like odor. It is miscible with water, ethanol and diethyl ether.

To oxygenate means to impregnate, combine, or supply something with oxygen, while oxygenates are hydrocarbons containing at least one oxygen atom that are used as fuel additives to promote complete combustion in fuel mixtures. Oxygenates can also be employed to reduce air pollution by reducing carbon monoxide production and soot particle size and compounds such as aromatic hydrocarbons, polyaromatic hydrocarbons, and nitrated polyaromatic hydrocarbons that are side-products caused by incomplete combustion.

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An antiknock agent is a gasoline additive used to reduce engine knocking and increase the fuel's octane rating by raising the temperature and pressure at which auto-ignition occurs. The mixture known as gasoline or petrol, when used in high compression internal combustion engines, has a tendency to knock and/or to ignite early before the correctly timed spark occurs.

The MTBE controversy concerns Methyl tert-butyl ether (MTBE), a gasoline additive that replaced tetraethyllead. MTBE is an oxygenate and raises gasoline's octane number. Its use declined in the United States in response to environmental and health concerns. It has polluted groundwater due to MTBE-containing gasoline being spilled or leaked at gas stations. MTBE spreads more easily underground than other gasoline components due to its higher solubility in water. Cost estimates for removing MTBE from groundwater and contaminated soil range from $1 billion to $30 billion, including removing the compound from aquifers and municipal water supplies, and replacing leaky underground oil tanks. Who will pay for remediation is controversial. In one case, the cost to oil companies to clean up the MTBE in wells belonging to the city of Santa Monica, California is estimated to exceed $200 million.

tert-Amyl methyl ether (TAME) is an ether used as a fuel oxygenate. TAME derives from C5 distillation fractions of naphtha. It has an ethereous odor. Unlike most ethers, it does not require a stabilizer as it does not form peroxides on storage.

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<i>tert</i>-Amyl ethyl ether Chemical compound

tert-Amyl ethyl ether (TAEE) is a chemical compound, classified as an ether, with the molecular formula C7H16O. It is used as an additive in gasoline fuels as an oxygenate and also as a solvent in organic chemistry.

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Reformulated Blendstock for Oxygenate Blending (RBOB) is a gasoline futures contract traded on the New York Mercantile Exchange (NYMEX). It is the benchmark futures contract for wholesale gasoline in the United States.

References

  1. 1 2 Record of Methyl tert-butyl ether in the GESTIS Substance Database of the Institute for Occupational Safety and Health
  2. ↑ "Methyl tertiary butyl ether prices, markets & analysis". ICIS Explore. Retrieved 2020-06-28.
  3. ↑ "Oxygenates". www.api.org. Retrieved 2020-06-28.
  4. ↑ "How is Methanol Produced". METHANOL INSTITUTE. Retrieved 2020-06-29.
  5. ↑ Anzelmo, Bryce; Wilcox, Jennifer; Liguori, Simona. "Hydrogen production via natural gas steam reforming in a Pd-Au membrane reactor. Investigation of reaction temperature and GHSV effects and long-term stability" (PDF). Journal of Membrane Science: 25–32.[ permanent dead link ]
  6. ↑ "methanol | Properties, Production, Uses, & Poisoning". Encyclopedia Britannica. Retrieved 2020-06-29.
  7. ↑ "Methyl Tertiary Butyl Ether (MTBE) Production and Manufacturing Process". ICIS Explore. Retrieved 2020-06-29.
  8. ↑ "The United States continues to export MTBE, mainly to Mexico, Chile, and Venezuela - Today in Energy - U.S. Energy Information Administration (EIA)". www.eia.gov. Retrieved 2020-06-28.
  9. ↑ "United States | Methyl Tertiary Butyl Ether (MTBE): Production | Economic Indicators". www.ceicdata.com. Retrieved 2020-06-28.
  10. ↑ "Aramco completes its acquisition of a 70% stake in SABIC from the Public Investment Fund (PIF)". www.saudiaramco.com. 17 June 2020. Retrieved 2020-06-29.
  11. ↑ "Saudi Aramco buys SABIC shares on market as it completes acquisition". Reuters. 2020-06-14. Retrieved 2020-06-29.
  12. ↑ "Saudi Aramco to have largest MTBE capacity in Middle East and Asia" . Retrieved 2020-06-29.
  13. ↑ "Saudi Aramco's MTBE trading volume likely to rise after Sabic purchase | S&P Global Platts". www.spglobal.com. 2019-04-09. Retrieved 2020-06-29.
  14. ↑ "MTBE annual production capacity globally 2023". Statista. Retrieved 2020-06-28.
  15. ↑ "Overview | Methyl Tertiary Butyl Ether (MTBE) | US EPA". archive.epa.gov. Retrieved 2021-04-07.
  16. ↑ "NExOCTANE™ - Neste Jacobs". www.nesteengineering.com. Archived from the original on January 6, 2006.
  17. ↑ "KBR - NExOCTANE™". Archived from the original on 2006-01-06. Retrieved 2006-01-31.
  18. ↑ Matyash, V.; Liebisch, G.; Kurzchalia, T. V.; Shevchenko, A.; Schwudke, D. (2008). "Lipid extraction by methyl-tert-butyl ether for high-throughput lipidomics". The Journal of Lipid Research . 49 (5): 1137–1146. doi: 10.1194/jlr.D700041-JLR200 . PMC   2311442 . PMID   18281723.
  19. ↑ Vopička, Ondřej; Pilnáček, Kryštof; Číhal, Petr; Friess, Karel (2016-03-01). "Sorption of methanol, dimethyl carbonate, methyl acetate, and acetone vapors in CTA and PTMSP: General findings from the GAB Analysis". Journal of Polymer Science Part B: Polymer Physics . 54 (5): 561–569. Bibcode:2016JPoSB..54..561V. doi:10.1002/polb.23945. ISSN   1099-0488.
  20. ↑ Vopička, Ondřej; Radotínský, Daniel; Friess, Karel (2016-02-01). "Sorption of vapour mixtures of methanol and dimethyl carbonate in PTMSP: Cooperative and competitive sorption in one system". European Polymer Journal . 75: 243–250. doi:10.1016/j.eurpolymj.2015.12.015.
  21. ↑ "Interaction between bromine and tert-butyl methyl ether". UK Chemical Reaction Hazards Forum. Archived from the original on 13 March 2011. Retrieved 13 May 2010.
  22. ↑ Zeon Corporation Archived 2011-07-22 at the Wayback Machine
  23. ↑ CRC Handbook of Chemistry and Physics , 90th edition
  24. ↑ Schoenfield LJ, Marks JW (1993). "Oral and contact dissolution of gallstones". Am. J. Surg. 165 (4): 427–30. doi:10.1016/S0002-9610(05)80934-1. PMID   8480875.
  25. ↑ "Health Guide: Gallstones". New York Times.
  26. ↑ San Francisco Bay Area Regional Water Quality Control Board Integrated Basin Management Plan (2004) Archived 2008-02-29 at the Wayback Machine
  27. ↑ link text Archived 2011-07-28 at the Wayback Machine
  28. ↑ Fischer A, Oehm C, Selle M, Werner P (2005). "Biotic and abiotic transformations of methyl tertiary butyl ether (MTBE)". Environ Sci Pollut Res Int. 12 (6): 381–6. doi:10.1065/espr2005.08.277. PMID   16305145. S2CID   97168152.
  29. ↑ "Methyl Tertiary Butyl Ether (MTBE) | US EPA".
  30. ↑ "California Reformulated Gasoline Phase 3". Sacramento, CA: California Air Resources Board. 2015-07-24. Archived from the original on 2018-04-07. Retrieved 2018-04-07.
  31. ↑ "Spill Response & Remediation FAQ". Chemical and Pollution Control. Albany, NY: New York State Department of Environmental Conservation. Retrieved 2018-04-06.
  32. ↑ State of New York. New York Consolidated Laws, Agriculture and Markets Law. "AGM § 192-g. Methyl tertiary butyl ether; prohibited."
  33. ↑ http://www.cnn.com/2005/POLITICS/04/21/energy.bill.mtbe.ap/ Archived 2005-04-22 at the Wayback Machine
  34. ↑ "House approves $12 billion energy package". NBC News . 2005-04-22.
  35. ↑ Charles Babington, House Again Passes GOP Energy Measures, Washington Post, June 16, 2004, at A4 (House passes Energy Bill, but Senate opponents of MTBE provision in House Bill have the votes to prevent its enactment).
  36. ↑ United States. Energy Policy Act of 2005. Pub. L. Tooltip Public Law (United States)  109–58 (text) (PDF). Approved 2005-08-08.
  37. ↑ "MTBE Cleanup Estimates". SIGMA Weekly Report. Fairfax, VA: Society of Independent Gasoline Marketers of America (SIGMA). 2005-05-23. Archived from the original on 2009-10-09.
  38. ↑ "Long Island Utility Fighting to Defeat MTBE Safe Harbor". The MTBE e-Resource. New York, NY: Napoli Bern, LLP. 2004-03-16. Archived from the original on 2007-10-20.
  39. ↑ "Oil Companies Pay Santa Monica MTBE Cleanup Costs". Environment News Service. Ecology Prime Media, Inc. 2005-02-17.
  40. ↑ Navarro, Mireya (2009-10-20). "City Awarded $105 Million in Exxon Mobil Lawsuit". The New York Times. Retrieved 2010-05-12.
  41. ↑ Earle, Sarah (2013-04-09). "Exxon Mobil is Found Negligent in New Hampshire MTBE Use". Bloomberg.
  42. ↑ EPA (1998-03-02). "Announcement of the Drinking Water Contaminant Candidate List." Federal Register, 63 FR 10274
  43. ↑ "Drinking Water Regulations Under Development or Review". EPA. 2020-01-27.
  44. ↑ "How EPA Regulates Drinking Water Contaminants". EPA. 2017-05-03.
  45. ↑ "MTBE: Regulations and Drinking Water Monitoring Results". Sacramento, CA: California State Water Resources Control Board. 2014-08-04.
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