| 词条 | Cumene process |
| 释义 |
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 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.[5] Steps of the processCumene is formed in the gas-phase Friedel-Crafts alkylation of benzene by propylene. 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 oxidized in air, which removes the tertiary benzylic hydrogen from cumene and hence forms a cumene radical: The cumene radical then bonds with an oxygen molecule to give cumene peroxide radical, which in turn forms cumene hydroperoxide (C6H5C(CH3)2-O-O-H) 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 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[6] and also the oxidation step of hydroboration-oxidation.[7] 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. Modifications and related reactionsModified cumene processes include different approaches. Mitsui & Co. developed additional step(s) to hydrogenating the acetone product and dehydrating the isopropanol product to propene, which is recycled as a starting reactant. Employing a starting feedstock mixture of 1 and 2-butenes, which is known as Raffinate-2, produces phenol and a mixture of acetone and butanone instead of only phenol and acetone in the original. Shell Chemicals in Houston, Texas could possibly employ such modification. [8] Hydroquinone, also known as benzene-1,4-diol, is prepared by dialkylation of benzene with propene to give 1,4-diisopropylbenzene. This compound reacts with air to afford the bis(hydroperoxide), which is structurally similar to cumene hydroperoxide and rearranges in acid to give acetone and hydroquinone. Oxidation of hydroquinone gives 1,4-Benzoquinone. In other words, 1,4-Benzoquinone is prepared by oxidation of diisopropylbenzene via a reaction related to the Hock rearrangement: C6H4(CHMe2)2 + 3 O2 → C6H4O2 + 2 OCMe2 + H2O The reaction proceeds via the bis(hydroperoxide). Acetone is a coproduct.[9] 2-Naphthol can also be produced by a method analogous to the cumene process.[10]See also
References1. ^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. ^{{webarchive |url=https://web.archive.org/web/20070409042033/http://www.chemistry.org/portal/a/c/s/1/feature_pro.html?id=c373e908e6e847ac8f6a17245d830100 |date=* |title=Direct Routes to Phenol}} 6. ^{{cite book|last=Streitwieser|first=A|author2=Heathcock, C.H.|others=Kosower, E.M.|title=Introduction to Organic Chemistry|publisher=MacMillan|location=New York|year=1992|edition=4th|pages=1018|chapter=30|isbn=0-02-418170-6}} 7. ^{{cite book|last=K.P.C.|first=Vollhardt|author2=N.E. Schore|authorlink2=Neil E. Schore|title=Organic Chemistry: Structure and Function|publisher=Freeman|location=New York|year=2003|edition=4th|pages=988|chapter=22|isbn=0-7167-4374-4}} 8. ^{{webarchive |url=https://web.archive.org/web/20070409042033/http://www.chemistry.org/portal/a/c/s/1/feature_pro.html?id=c373e908e6e847ac8f6a17245d830100 |date=* |title=Direct Routes to Phenol}} 9. ^Gerhard Franz, Roger A. Sheldon "Oxidation" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2000 {{DOI|10.1002/14356007.a18_261}} 10. ^Gerald Booth "Naphthalene Derivatives" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. {{DOI|10.1002/14356007.a17_009}}. External links
1 : Chemical processes |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。