Dehydrogenation

Source: Wikipedia, the free encyclopedia.
Compare Deprotonation.

In

aromatics.[1] As a problematic reaction, the fouling and inactivation of many catalysts arises via coking, which is the dehydrogenative polymerization of organic substrates.[2]

dehydrogenases
.

Heterogeneous catalytic routes

Styrene

Dehydrogenation processes are used extensively to produce aromatics in the

unsaturated fats. One of the largest scale dehydrogenation reactions is the production of styrene by dehydrogenation of ethylbenzene. Typical dehydrogenation catalysts are based on iron(III) oxide, promoted by several percent potassium oxide or potassium carbonate.[4]

C6H5CH2CH3 → C6H5CH=CH2 + H2

Other alkenes

The cracking processes especially fluid catalytic cracking and steam cracker produce high-purity mono-olefins from

chromium (III) oxide catalyst at 500 °C. Target products are propylene, butenes, and isopentane, etc. These simple compounds are important raw materials for the synthesis of polymers and gasoline additives.[citation needed
]

Oxidative dehydrogenation

Relative to thermal cracking of alkanes, oxidative dehydrogenation (ODH) is of interest for two reasons: (1) undesired reactions take place at high temperature leading to coking and catalyst deactivation, making frequent regeneration of the catalyst unavoidable, (2) thermal dehydrogenation is expensive as it requires a large amount of heat. Oxidative dehydrogenation (ODH) of n-butane is an alternative to classical dehydrogenation, steam cracking and fluid catalytic cracking processes.[5][6]

vanadium oxides. In the commonly used formox process, methanol and oxygen react at ca. 250–400 °C in presence of iron oxide in combination with molybdenum and/or vanadium to produce formaldehyde according to the chemical equation:[9]

CH3OH + O2 → 2 CH2O + 2 H2O

Homogeneous catalytic routes

A variety of dehydrogenation processes have been described for

pincer complexes.[13][14]

Stoichiometric processes

Dehydrogenation of amines to

reagents, such as Iodine pentafluoride (IF
5).[citation needed
]

In typical aromatization, six-membered alicyclic rings, e.g. cyclohexene, can be aromatized in the presence of hydrogenation acceptors. The elements sulfur and selenium promote this process. On the laboratory scale, quinones, especially 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) are effective.[citation needed]

Main group hydrides

Dehydrogenation of ammonia borane.

The dehydrogenative coupling of silanes has also been developed.[15]

n PhSiH3 → [PhSiH]n + n H2

The dehydrogenation of amine-boranes is related reaction. This process once gained interests for its potential for hydrogen storage.[16]

References

  1. ^
    ISBN 9780471651543
    .
  2. doi:10.1016/S0926-860X(00)00845-0
    .
  3. ISBN 9780471651543
    .
  4. ^ Denis H. James William M. Castor, "Styrene" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.
  5. doi:10.1016/j.cattod.2012.07.013
    .
  6. ISBN 978-0615702162
    .
  7. ISSN 0926-860X
    .
  8. ISSN 1381-1169
    .
  9. doi:10.1002/14356007.a11_619
  10. PMID 21391561
    .
  11. PMID 19938813
    .
  12. PMID 21391566
    .
  13. ^ "1". Alkane C-H Activation by Single-Site Metal Catalysis | Pedro J. Pérez | Springer. pp. 1–15.
  14. ISBN 9789048136971
    .
  15. doi:10.1139/v87-303
    .
  16. PMID 20672860
    .
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