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Methyl Tert Butyl Ether

Common name: Methyl Tertiary Butyl Ether
Molecular Formula: C5H12O
Chemical name: 2-Methoxy-2-methyl-propane

Introduced as an octane replacement for tetraethyl lead in the 1970s, MTBE was used as an oxygenating agent added to ~30% of U.S. gasoline supply to reduce carbon monoxide emissions of automobiles and meet air quality standards. Almost the entire production of MTBE (9.1 billion pounds in 1992 by 27 companies in the United States) was used as a gasoline additive. Since then, addition of MTBE to gasoline has been phased out by the US EPA and its use as a fuel additive in the US is banned. Alternative uses continue.

mtbe

Solubility: In water, 51.26 g/L @ 25°C

Environmental Fate: Methyl tertiary-butyl ether evaporates when exposed to air and has a turpentine-like odor. Once in air, it is expected to break down to other chemicals and can contribute to the formation of photochemical smog when it reacts with other volatile organic carbon substances in air. MBTE dissolves when mixed with water and does not bind well to soil. In numerous locations, MTBE has reached the groundwater through leaky underground gasoline storage tanks and entered groundwater. In 1999, it was estimated that between 5 and 10% of community drinking water supplies in high MTBE use areas had detectable MTBE levels; as many as 9000 community water supply wells in 31 states may be affected. In Santa Monica, CA, 7 wells supplying half of the community’s water were closed because of MBTE contamination above the action level. Although a xenobiotic and relatively recalcitrant to biodegradation, there is evidence that naturally-occurring microorganisms in sediments can aerobically degrade MTBE to CO2. MTBE is considered a potential human carcinogen and legislation restricts its use. On 20 Mar 2000, EPA administrator Carol M. Browner stated that “Americans deserve both clean air and clean water and never one at the expense of the other” and announced a proposed legislative ban on MTBE, expected to take three years to implement, and amendments to the Clean Air Act that would maintain or increase the use of ethanol in fuel.

Other oxygenates used in gasoline are ethanol, TAME (tertiary amyl methyl ether), TBA (tertiary butyl alcohol), DIPE (di-isopropyl ether), and ETBE (ethyl tertiary butyl ether).

CAS No: 1634-04-4

mtbe_tetra

U.S. Environmental Protection Agency (EPA). 1994. Chemicals in the environment: Methyl-tert-butyl-ether (CAS No. 1634-04-4). OPPT Chemical Fact Sheet.

U.S. Environmental Protection Agency (EPA). 1994. Chemical summary for methyl-tert-butyl ether.

Bradley, P.M., J.E. Landmeyer, and F.H. Chapelle. 1999. Aerobic mineralization of MTBE and tert-butyl alcohol by stream-bed sediment microorganisms. Environ. Sci Technol. 33:1877-1879.

Johnson, R., J. Pankow, D. Bender, C Price, and J. Zagorski. 2000. MTBE: To what extent will past releases contaminate community water supply wells. Environ. Sci Technol. 34:[May 1 2000; available on-line at http://pubs.acs.org/hotartcl/est/2000/research