In
chemistry, the Halcon process refers to technology for the production of
propylene oxide
Propylene oxide is an acutely toxic and carcinogenic organic compound with the molecular formula CH3CHCH2O. This colourless volatile liquid with an odour similar to ether, is produced on a large scale industrially. Its major application is its us ...
by oxidation of
propylene
Propylene, also known as propene, is an unsaturated organic compound with the chemical formula CH3CH=CH2. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colorless gas with a faint petro ...
with
tert-butyl hydroperoxide
''tert''-Butyl hydroperoxide (tBuOOH) is the organic compound with the formula (CH3)3COOH. It is one of the most widely used hydroperoxides in a variety of oxidation processes, for example the Halcon process. It is normally supplied as a 69– ...
. The reaction requires metal
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 recyc ...
s, which typically contain
molybdenum:
:(CH
3)
3COOH + CH
2=CHCH
3 → (CH
3)
3COH + CH
2OCHCH
3
The byproduct
tert-butanol
''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 r ...
is recycled or converted to other useful compounds. The process once operated at the scale of >2 billion kg/y.
The lighter analogue of propylene oxide,
ethylene oxide
Ethylene oxide is an organic compound with the formula . It is a cyclic ether and the simplest epoxide: a three-membered ring consisting of one oxygen atom and two carbon atoms. Ethylene oxide is a colorless and flammable gas with a faintly sw ...
, is produced by silver-catalyzed reaction of
ethylene with
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...
. Attempts to implement this relatively simple technology to the conversion of
propylene
Propylene, also known as propene, is an unsaturated organic compound with the chemical formula CH3CH=CH2. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colorless gas with a faint petro ...
to
propylene oxide
Propylene oxide is an acutely toxic and carcinogenic organic compound with the molecular formula CH3CHCH2O. This colourless volatile liquid with an odour similar to ether, is produced on a large scale industrially. Its major application is its us ...
fail. Instead only combustion predominates. The problems are attributed to the sensitivity of
allylic C-H bonds.
Mechanism
The oxidation is thought to proceed by formation of Mo(η
2-O
2-tert-Bu) complexes. The peroxy O center is rendered highly electrophilic, leading to attack on the alkene.
History
The Halcon process was developed by
Halcon International.
[{{cite journal , doi=10.1021/cen-v059n007.p016, title=Ralph Landau wins 1981 Perkin Medal, year=1981, last1=Fallwell, first1=William, journal=Chemical & Engineering News Archive, volume=59, issue=7, page=16]
References
Catalysis