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The cumene process (cumene-phenol process, Hock 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. It was invented by Heinrich Hock in 1944[1][2] and independently by R. Ūdris and P. Sergeyev in 1942 (USSR).[3]

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. In 2003, nearly 7 million tonnes of phenol was produced by the cumene process.[4] In order for this process to be economical, there must also be demand for the acetone by-product as well as the phenol.

Overview of the cumene process

Technical description[edit]

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 aluminium halides. Cumene is formed in the gas-phase Friedel-Crafts alkylation of benzene by propylene:


Cumene is oxidized in air 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 (C6H5C(CH3)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 (the Hock rearrangement) to give phenol and acetone. In the first step, the terminal hydroperoxy oxygen atom is protonated. This is followed by a step in which the phenyl group migrates from the benzyl carbon to the adjacent oxygen and a water molecule is lost, producing a resonance stabilized tertiary carbocation. The concerted mechanism of this step is similar to the mechanisms of the Baeyer-Villiger oxidation[5] and also the oxidation step of hydroboration-oxidation.[6] In 2009, an acidified bentonite clay was proven to be a more economical catalyst than sulfuric acid as the acid medium.


As shown below, the resulting carbocation is then attacked by water, a proton is then transferred from the hydroxy oxygen to the ether oxygen, and finally the ion falls apart into phenol and acetone.


The products are separated by distillation.


  1. ^ Hock, H. and Lang, S. (1944), Autoxydation von Kohlenwasserstoffen, IX. Mitteil.: Über Peroxyde von Benzol-Derivaten. Berichte der deutschen chemischen Gesellschaft (A and B Series), 77: 257–264 doi:10.1002/cber.19440770321
  2. ^ Concise Encyclopedia Chemistry (1993) Mary Eagleso
  3. ^ http://izgudrojumi.lza.lv/izg_en.php?id=54
  4. ^ Manfred Weber, Markus Weber, Michael Kleine-Boymann "Phenol" in Ullmann's Encyclopedia of Industrial Chemistry 2004, Wiley-VCH. doi:10.1002/14356007.a19_299.pub2.
  5. ^ Streitwieser, A; Heathcock, C.H. (1992). "30". Introduction to Organic Chemistry. Kosower, E.M. (4th ed.). New York: MacMillan. p. 1018. ISBN 0-02-418170-6. 
  6. ^ K.P.C., Vollhardt; N.E. Schore (2003). "22". Organic Chemistry: Structure and Function (4th ed.). New York: Freeman. p. 988. ISBN 0-7167-4374-4. 

See also[edit]

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4 news items


Tue, 09 Jun 2015 15:47:43 -0700

Due to a conversion inefficiency in the cumene process, benzene costs are absorbed by sellers in a falling market. Following an uptick in May, the June benzene contract settled at $2.25/gal, a decrease of 59 cents/gal. The June benzene movement could ...
Chemicals Technology
Tue, 26 May 2015 03:13:49 -0700

"The new catalysis is claimed to eliminate unnecessary by-products and energy-consumption." Unlike cumene process to produce phenol, the new catalysis is claimed to eliminate unnecessary by-products and energy-consumption. For oxidation of propylene ...
Business Standard
Thu, 28 May 2015 01:01:11 -0700

The existing three-step process for production of phenol, called the cumene process, is energy-consuming, environmentally unfavourable, and disadvantageous for practical operation. This process also produces unnecessary by- products, such as acetone ...

Business Standard

Business Standard
Mon, 29 Dec 2014 20:44:58 -0800

Phenol and acetone are produced from benzene and propylene through the cumene process. Phenol prices have halved from $1,620 a tonne in early August to $850 last week. Phenol has several uses, plywood makers use phenol to laminate wood with ...

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