Isobutylene
Encyclopedia
Isobutylene is a hydrocarbon
of significant industrial importance. It is a four-carbon branched alkene
(olefin), one of the four isomers of butylene
. At standard temperature and pressure it is a colorless flammable gas.
and ethanol
in the manufacture of the gasoline oxygenates methyl tert-butyl ether
(MTBE) and ethyl tert-butyl ether (ETBE), respectively. Alkylation
with butane produces isooctane, another fuel additive. Isobutylene is also used in the production of methacrolein
. Polymerization
of isobutylene produces butyl rubber
(polyisobutylene). Antioxidants such as butylated hydroxytoluene
(BHT) and butylated hydroxyanisole
(BHA) are produced by Friedel-Crafts alkylation of phenol
s using isobutylene.
, but the most common industrial method for its production is by catalytic
dehydrogenation
of isobutane
. In the 1990s, the production of isobutylene increased dramatically as the demand for oxygenates such as MTBE grew. Key manufacturers of this product are Texas Petrochemicals(TPC Group) and Lyondell in North America.
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
of significant industrial importance. It is a four-carbon branched alkene
Alkene
In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...
(olefin), one of the four isomers of butylene
Isomers of butylene
Butene, also known as butylene, is an alkene with the formula C4H8. It is a colourless gas that is present in crude oil as a minor constituent in quantities that are too small for viable extraction. It is therefore obtained by catalytic cracking of long chain hydrocarbons left during refining of...
. At standard temperature and pressure it is a colorless flammable gas.
Uses
Isobutylene is used as an intermediate in the production of a variety of products. It is reacted with methanolMethanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...
and ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
in the manufacture of the gasoline oxygenates methyl tert-butyl ether
Methyl tert-butyl ether
Methyl tert-butyl ether, also known as methyl tertiary butyl ether and MTBE, is an organic compound with molecular formula 3COCH3. MTBE is a volatile, flammable, and colorless liquid that is immiscible with water. It has a minty odor vaguely reminiscent of diethyl ether, leading to unpleasant taste...
(MTBE) and ethyl tert-butyl ether (ETBE), respectively. Alkylation
Alkylation
Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbene . Alkylating agents are widely used in chemistry because the alkyl group is probably the most common group encountered in...
with butane produces isooctane, another fuel additive. Isobutylene is also used in the production of methacrolein
Methacrolein
Methacrolein, or methacrylaldehyde, is an unsaturated aldehyde. It is a clear, colorless, flammable liquid that is present in cigarettes when smoking.Industrially, the primary use of methacrolein is in the manufacture of polymers and synthetic resins....
. Polymerization
Polymerization
In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains...
of isobutylene produces butyl rubber
Butyl rubber
Butyl rubber 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, n, is the homopolymer of isobutylene, or 2-methyl-1-propene, on which butyl rubber is based...
(polyisobutylene). Antioxidants such as butylated hydroxytoluene
Butylated hydroxytoluene
Butylated hydroxytoluene , also known as butylhydroxytoluene, is a lipophilic organic compound that is primarily used as an antioxidant food additive as well as an antioxidant additive in cosmetics, pharmaceuticals, jet fuels, rubber, petroleum products, electrical transformer oil, and embalming...
(BHT) and butylated hydroxyanisole
Butylated hydroxyanisole
Butylated hydroxyanisole is an antioxidant consisting of a mixture of two isomeric organic compounds, 2-tert-butyl-4-hydroxyanisole and 3-tert-butyl-4-hydroxyanisole. It is prepared from 4-methoxyphenol and isobutylene. It is a waxy solid used as a food additive with the E number E320...
(BHA) are produced by Friedel-Crafts alkylation of phenol
Phenol
Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...
s using isobutylene.
Manufacture
Isobutylene can be isolated from refinery streams by reaction with sulfuric acidSulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
, but the most common industrial method for its production is by catalytic
Catalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
dehydrogenation
Dehydrogenation
Dehydrogenation is a chemical reaction that involves the elimination of hydrogen . It is the reverse process of hydrogenation. Dehydrogenation reactions may be either large scale industrial processes or smaller scale laboratory procedures....
of isobutane
Isobutane
Isobutane, also known as methylpropane, is an isomer of butane. It is the simplest alkane with a tertiary carbon. Concerns with depletion of the ozone layer by freon gases have led to increased use of isobutane as a gas for refrigeration systems, especially in domestic refrigerators and freezers,...
. In the 1990s, the production of isobutylene increased dramatically as the demand for oxygenates such as MTBE grew. Key manufacturers of this product are Texas Petrochemicals(TPC Group) and Lyondell in North America.