Everything about Cumene Process totally explained
Cumene process is an
industrial process for developing
phenol and
acetone from
benzene and
propylene. The term stems from
cumene (isopropyl benzene), the intermediate material during the process.
This process converts two relatively cheap starting materials,
benzene and
propylene, into two more valuable ones, phenol and acetone. Other reactants required are
oxygen from air and small amounts of a
radical initiator. Most of the worldwide production of phenol and acetone is now based on this method.
The overall chemical process is summarised below.
Technical description
Benzene and propylene are compressed together to a pressure of 30
standard atmospheres at 250 °
C (482°
F) in presence of a
catalytic Lewis acid.
Phosphoric acid is often favored over
aluminum halides. Cumene is formed in the gas-phase
Friedel-Crafts alkylation of benzene by propylene:
Cumene is oxidized in slightly
basic conditions in presence of a
radical initiator, which removes the tertiary
benzylic hydrogen from cumene and hence forms a cumene
radical:
This cumene radical then
bonds with an oxygen molecule to give cumene
hydroperoxide radical, which in turn forms cumene hydroperoxide (C
6H
5C(CH
3)
2-O-O-H) by abstracting benzylic hydrogen from another cumene molecule. This latter cumene converts into cumene radical and feeds back into subsequent chain formations of cumene hydroperoxides. A pressure of 5 atm is used to ensure that the unstable peroxide is kept in liquid state.
Cumene hydroperoxide is then
hydrolysed in an
acidic medium to give
phenol and
acetone. Loss of a water molecule from the hydroperoxide leaves an
electron-deficient oxygen. Migration of the phenyl to the oxygen leads to a more stable
resonance hybridized structure of tertiary benzylic radical, which in turn produce acetone and phenol after an attachment of a water molecule and rearrangement. Research suggests the loss of water molecule and phenyl migration may take place simultaneously, in other words the step of the mechanism is concerted.
The products are extracted by
distillation.
Further Information
Get more info on 'Cumene Process'.
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