Isobutylene (or 2-methylpropene) is a
hydrocarbon with the
chemical formula . 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.
Production
Polymer and chemical grade isobutylene is typically obtained by dehydrating
tertiary butyl alcohol (TBA) or
catalytic
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recy ...
dehydrogenation of
isobutane (Catofin or similar processes).
[.] Gasoline additives
methyl tert-butyl ether (MTBE) and
ethyl tert-butyl ether
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 etha ...
(ETBE), respectively, are produced by reacting
methanol or
ethanol with isobutylene contained in butene streams from olefin steam crackers or refineries, or with isobutylene from dehydrated TBA. Isobutylene is not isolated from the olefin or refinery butene stream before the reaction, as separating the ethers from the remaining butenes is simpler. Isobutylene can also be produced in high purities by "back-cracking" MTBE or ETBE at high temperatures and then separating the isobutylene by distillation from methanol or
Isobutylene is a byproduct in the
ethenolysis of
diisobutylene to prepare
neohexene:
:
Uses
Isobutylene is used in the production of a variety of products. It is alkylated with butane to produce
isooctane or dimerized to diisobutylene (DIB) and then hydrogenated to make
isooctane, a fuel additive. Isobutylene is also used in the production of
methacrolein.
Polymerization of isobutylene produces
butyl rubber
Butyl rubber, sometimes just called "butyl", is a synthetic rubber, a copolymer of isobutylene with isoprene. The abbreviation IIR stands for isobutylene isoprene rubber. Polyisobutylene, also known as "PIB" or polyisobutene, (C4H8)n, is the h ...
(polyisobutylene or PIB). Antioxidants such as
butylated hydroxytoluene (BHT) and
butylated hydroxyanisole
Butylated hydroxyanisole (BHA) is a synthetic, waxy, solid petrochemical. Its antioxidant properties have caused it to be widely used as a preservative in food, food packaging, animal feed, cosmetics, pharmaceuticals, rubber, and petroleum produc ...
(BHA) are produced by
Friedel-Crafts alkylation of
phenols with isobutylene.
''tert''-Butylamine is produced commercially by amination of isobutylene using
zeolite
Zeolites are microporous, crystalline aluminosilicate materials commonly used as commercial adsorbents and catalysts. They mainly consist of silicon, aluminium, oxygen, and have the general formula ･y where is either a metal ion or H+. These p ...
catalyst
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recy ...
s:
:
NH3 + CH2=C(CH3)2 -> H2NC(CH3)3
Safety
Isobutylene is a highly flammable gas.
See also
*
Butyl rubber
Butyl rubber, sometimes just called "butyl", is a synthetic rubber, a copolymer of isobutylene with isoprene. The abbreviation IIR stands for isobutylene isoprene rubber. Polyisobutylene, also known as "PIB" or polyisobutene, (C4H8)n, is the h ...
*
Polythene
*
Polybutene Polybutene is an organic polymer made from a mixture of 1-butene, 2-butene, and isobutylene. Ethylene steam cracker C4s are also used as supplemental feed for polybutene. It is similar to polyisobutylene (PIB), which is produced from essentially ...
References
External links
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{{Hydrocarbons
Alkenes