The cumene process (cumene-phenol process, Hock process) is an industrial process for synthesizing phenol and acetone from benzene and propylene. The term stems from cumene (isopropyl benzene), the intermediate material during the process. It was invented by R. Ūdris and P. Sergeyev in 1942 (USSR),[1] and independently by Heinrich Hock in 1944.[2][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 2022, nearly 10.8 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.[5]
First stage of Hock process: alkylation of benzene with propylene.Second stage of Hock process: autoxidation of cumene.
The cumene radical then bonds with an oxygen molecule to give cumene peroxide radical, which in turn forms cumene hydroperoxide (C6H5C(CH3)2O2H) by abstracting a 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 undergoes a rearrangement reaction 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[6] and Criegee rearrangement reactions, and also the oxidation step of the hydroboration–oxidation process.[7] In 2009, an acidified bentonite clay was proven to be a more economical catalyst than sulfuric acid as the acid medium.
The resulting carbocation is then attacked by water, forming a hemiacetal-like structure. After transfer of a proton from the hydroxy oxygen to the ether oxygen, the ion falls apart into phenol and acetone.
Related reactions and modificationsedit
Alternatives to acetone co-productionedit
Cyclohexylbenzene can replace isopropylbenzene. Via the Hock rearrangement, cyclohexylbenzene hydroperoxide cleaves to give phenol and cyclohexanone. Cyclohexanone is an important precursor to some nylons.[8]
Starting with the alkylation of benzene with mixture of 1 and 2-butenes, the cumene process produces phenol and butanones.[5]
Alternatives to phenol productionedit
Hydroquinone is prepared by dialkylation of benzene with propene to give 1,4-diisopropylbenzene. This compound reacts with air to afford the bis(hydroperoxide). Analogous to the behavior of cumene hydroperoxide, it rearranges in acid to give acetone and hydroquinone. Oxidation of hydroquinone gives 1,4-benzoquinone:[9]
Resorcinol is analogously prepared by converting 1,3-Diisopropylbenzene into the bis(hydroperoxide), which fragments to resorcinol and acetone.[10]
2-Naphthol can also be produced by a method analogous to the cumene process.[11]
3-Chlorophenol, which does not arise by chlorination of phenol, can be produced by Cumene process beginning with the alkylation of chlorobenzene with propylene.[12]
Crude acetone is hydrogenated in the liquid phase over Raney nickel or a mixture of copper and chromium oxide to give isopropyl alcohol. This process is useful, when it is coupled with excess acetone production.[14]Mitsui & Co. developed additional step(s) to hydrogenating acetone and dehydrogenating the isopropanol product to propene, which is recycled as a starting reactant.[5]
^. Archived from the original on 2016-03-03. Retrieved 2011-02-27.
^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
^Concise Encyclopedia Chemistry (1993) Mary Eagleso
^Roger A. Sheldon (1983). Patai, Saul (ed.). Syntheses and Uses of Hydroperoxides and Dialkylperoxides. PATAI'S Chemistry of Functional Groups. John Wiley & Sons. doi:10.1002/9780470771730.ch6.
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April 15, 2024
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The cumene process cumene phenol process Hock process is an industrial process for synthesizing phenol and acetone from benzene and propylene The term stems from cumene isopropyl benzene the intermediate material during the process It was invented by R udris and P Sergeyev in 1942 USSR 1 and independently by Heinrich Hock in 1944 2 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 2022 nearly 10 8 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 5 First stage of Hock process alkylation of benzene with propylene Second stage of Hock process autoxidation of cumene Contents 1 Steps of the process 2 Related reactions and modifications 2 1 Alternatives to acetone co production 2 2 Alternatives to phenol production 2 3 Acetone processing 2 4 Byproducts 3 See also 4 References 5 External linksSteps of the process editCumene is formed in the gas phase Friedel Crafts alkylation of benzene by propene Benzene and propene are compressed together to a pressure of 30 standard atmospheres at 250 C in presence of a catalytic Lewis acid Phosphoric acid is often favored over aluminium halides Cumene is oxidized in air which removes the tertiary benzylic hydrogen from cumene and hence forms a cumene radical nbsp dd The cumene radical then bonds with an oxygen molecule to give cumene peroxide radical which in turn forms cumene hydroperoxide C6H5C CH3 2O2H by abstracting a 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 nbsp nbsp dd Cumene hydroperoxide undergoes a rearrangement reaction 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 6 and Criegee rearrangement reactions and also the oxidation step of the hydroboration oxidation process 7 In 2009 an acidified bentonite clay was proven to be a more economical catalyst than sulfuric acid as the acid medium nbsp dd The resulting carbocation is then attacked by water forming a hemiacetal like structure After transfer of a proton from the hydroxy oxygen to the ether oxygen the ion falls apart into phenol and acetone nbsp dd Related reactions and modifications editAlternatives to acetone co production edit Cyclohexylbenzene can replace isopropylbenzene Via the Hock rearrangement cyclohexylbenzene hydroperoxide cleaves to give phenol and cyclohexanone Cyclohexanone is an important precursor to some nylons 8 Starting with the alkylation of benzene with mixture of 1 and 2 butenes the cumene process produces phenol and butanones 5 Alternatives to phenol production edit Hydroquinone is prepared by dialkylation of benzene with propene to give 1 4 diisopropylbenzene This compound reacts with air to afford the bis hydroperoxide Analogous to the behavior of cumene hydroperoxide it rearranges in acid to give acetone and hydroquinone Oxidation of hydroquinone gives 1 4 benzoquinone 9 C6H4 CHMe2 2 212O2 C6H4O2 2OCMe2 H2O displaystyle ce C6H4 CHMe2 2 2 1 2 O2 gt C6H4O2 2 OCMe2 H2O nbsp Resorcinol is analogously prepared by converting 1 3 Diisopropylbenzene into the bis hydroperoxide which fragments to resorcinol and acetone 10 2 Naphthol can also be produced by a method analogous to the cumene process 11 3 Chlorophenol which does not arise by chlorination of phenol can be produced by Cumene process beginning with the alkylation of chlorobenzene with propylene 12 Cresols are produced from isopropyltoluene 13 Acetone processing edit Crude acetone is hydrogenated in the liquid phase over Raney nickel or a mixture of copper and chromium oxide to give isopropyl alcohol This process is useful when it is coupled with excess acetone production 14 Mitsui amp Co developed additional step s to hydrogenating acetone and dehydrogenating the isopropanol product to propene which is recycled as a starting reactant 5 Byproducts edit Byproducts of the cumene process to produce phenol and acetone are acetophenone and alpha methylstyrene See also editBisphenol A Dow process phenol Friedel Crafts alkylation Baeyer Villiger oxidation Raschig Hooker process also produces phenol References edit Latvian Archived from the original on 2016 03 03 Retrieved 2011 02 27 Hock H and Lang S 1944 Autoxydation von Kohlenwasserstoffen IX Mitteil Uber Peroxyde von Benzol Derivaten Berichte der deutschen chemischen Gesellschaft A and B Series 77 257 264 doi 10 1002 cber 19440770321 Concise Encyclopedia Chemistry 1993 Mary Eagleso Phenol Market Size Share Analysis amp Forecast 2035 ChemAnalyst ChemAnalyst Retrieved 2024 04 09 a b c Direct Routes to Phenol Archived from the original on 2007 04 09 Retrieved 2006 12 26 Streitwieser A Heathcock C H 1992 30 Introduction to Organic Chemistry Kosower E M 4th ed New York MacMillan pp 1018 ISBN 0 02 418170 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 Plotkin Jeffrey S 2016 03 21 What s New in Phenol Production American Chemical Society Archived from the original on 2019 10 27 Retrieved 2018 01 02 Gerhard Franz Roger A Sheldon Oxidation in Ullmann s Encyclopedia of Industrial Chemistry Wiley VCH Weinheim 2000 doi 10 1002 14356007 a18 261 K W Schmiedel D Decker 2012 Resorcinol Ullmann s Encyclopedia of Industrial Chemistry Weinheim Wiley VCH doi 10 1002 14356007 a23 111 pub2 ISBN 978 3527306732 Gerald Booth Naphthalene Derivatives in Ullmann s Encyclopedia of Industrial Chemistry 2005 Wiley VCH Weinheim doi 10 1002 14356007 a17 009 Francois Muller Liliane Caillard 2011 Chlorophenols Ullmann s Encyclopedia of Industrial Chemistry Weinheim Wiley VCH doi 10 1002 14356007 a07 001 pub2 ISBN 978 3527306732 Roger A Sheldon 1983 Patai Saul ed Syntheses and Uses of Hydroperoxides and Dialkylperoxides PATAI S Chemistry of Functional Groups John Wiley amp Sons doi 10 1002 9780470771730 ch6 Papa A J Propanols Ullmann s Encyclopedia of Industrial Chemistry Weinheim Wiley VCH doi 10 1002 14356007 a22 173 ISBN 978 3527306732 External links editPhenol The essential chemical industry online nbsp Wikimedia Commons has media related to Cumene process Retrieved from https en wikipedia org w index php title Cumene process 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