Carbocatalysis

Image:Carbocatalysis.png

Carbocatalysis is a form of catalysis that uses heterogeneous carbon materials for the transformation or synthesis of organic or inorganic substrates. The catalysts are characterized by their high surface areas, surface functionality, and large, aromatic basal planes. Carbocatalysis can be distinguishable from supported catalysis (such as palladium on carbon) in that no metal is present, or if metals are present they are not the active species.

As of 2010, the mechanisms of reactivity are not well understood.{{citation needed|date=July 2010}}

One of the most common examples of carbocatalysis is the oxidative dehydrogenation of ethylbenzene to styrene discovered in the 1970s.{{cite journal | last1 = Alkhazov | first1 = T. G. | last2 = Lisovskii | first2 = A. E. | last3 = Gulakhmedova | first3 = T. Kh. | year = 1979 | title = Oxidative dehydrogenation of ethylbenzene over a charcoal catalyst | journal = React. Kinet. Catal. Lett. | volume = 12 | issue = 2 | pages = 189–193 | doi = 10.1007/BF02071909 }} Also in the industrial process of (non-oxidative) dehydrogenation of ethylbenzene, the potassium-promoted iron oxide catalyst is coated with a carbon layer as the active phase. In another early example,{{cite journal | last1 = Byung | first1 = H. H. | last2 = Dae | first2 = H. S. | last3 = Sung | first3 = Y. C. | year = 1985 | title = Graphite catalyzed reduction of aromatic and aliphatic nitro compounds with hydrazine hydrate | journal = Tetrahedron Lett. | volume = 26 | issue = 50 | pages = 6233–6234 | doi = 10.1016/S0040-4039(00)95060-3 }} a variety of substituted nitrobenzenes were reduced to the corresponding aniline using hydrazine and graphite as the catalyst.

The discovery of nanostructured carbon allotropes such as carbon nanotubes,{{cite journal | last1 = Iijima | first1 = S. | year = 1991 | title = Helical microtubules of graphitic carbon | journal = Nature | volume = 354 | issue = 6348 | pages = 56–58 | doi = 10.1038/354056a0 | bibcode=1991Natur.354...56I}} fullerenes,{{cite journal | last1 = Kroto | first1 = H. W. | last2 = Heath | first2 = J. R. | last3 = O'Brien | first3 = S. C. | last4 = Curl | first4 = R. F. | last5 = Smalley | first5 = R. E. | year = 1985 | title = C₆₀: Buckminsterfullerene | journal = Nature | volume = 318 | issue = 6042 | pages = 162–163 | doi = 10.1038/318162a0 | bibcode=1985Natur.318..162K}} or graphene{{cite journal | last1 = Novoselov | first1 = K. S. | last2 = Geim | first2 = A. K. | last3 = Morozov | first3 = S. V. | last4 = Jiang | first4 = D. | last5 = Zhang | first5 = Y. | last6 = Dubonos | first6 = S. V. | last7 = Grigorieva | first7 = I. V. | last8 = Firsov | first8 = A. A. | year = 2004 | title = Electric Field Effect in Atomically Thin Carbon Films | journal = Science | volume = 306 | issue = 5696 | pages = 666–669 | doi = 10.1126/science.1102896 | pmid=15499015|arxiv = cond-mat/0410550 |bibcode = 2004Sci...306..666N }} promoted further developments. Oxidized carbon nanotubes were used to dehydrogenate n-butane to 1-butene,{{cite journal | last1 = Zhang | first1 = J. | last2 = Liu | first2 = X. | last3 = Blume | first3 = R. | last4 = Zhang | first4 = A. | last5 = Schlögl | first5 = R. | last6 = Su | first6 = D. S. | year = 2008 | title = Surface-Modified Carbon Nanotubes Catalyze Oxidative Dehydrogenation of n-Butane | url = http://pubman.mpdl.mpg.de/pubman/item/escidoc:737077/component/escidoc:737076/378851_Sci322_73-77.pdf| journal = Science | volume = 322 | issue = 5898 | pages = 73–77 | doi = 10.1126/science.1161916 | pmid=18832641|bibcode = 2008Sci...322...73Z | hdl = 11858/00-001M-0000-0010-FE91-E | hdl-access = free }} and to selectively oxidize acrolein to acrylic acid.{{cite journal | last1 = Frank | first1 = B. | last2 = Blume | first2 = R. | last3 = Rinaldi | first3 = A. | last4 = Trunschke | first4 = A. | last5 = Schlögl | first5 = R. | year = 2011 | title = Oxygen Insertion Catalysis by sp² Carbon | journal = Angew. Chem. Int. Ed. | volume = 50 | issue = 43 | pages = 10226–10230 | doi = 10.1002/anie.201103340 | pmid = 22021211 | doi-access = free | hdl = 11858/00-001M-0000-0012-0B9A-8 | hdl-access = free }} Fullerenes were used in the catalytic reduction of nitrobenzene to aniline in the presence of H₂.{{cite journal | last1 = Li | first1 = B. | last2 = Xu | first2 = Z. | year = 2009 | title = A Nonmetal Catalyst for Molecular Hydrogen Activation with Comparable Catalytic Hydrogenation Capability to Noble Metal Catalyst | journal = J. Am. Chem. Soc. | volume = 131 | issue = 45 | pages = 16380–16382 | doi = 10.1021/ja9061097 | pmid=19845383}} Graphene oxide was used as a carbocatalyst to facilitate the oxidation of alcohols to the corresponding aldehydes/ketones (shown in the picture), the hydration of alkynes, and the oxidation of alkenes.{{cite journal | last1 = Dreyer | first1 = D. R. | last2 = Jia | first2 = H.-P. | last3 = Bielawski | first3 = C. W. | year = 2010 | title = Graphene Oxide: A Convenient Carbocatalyst for Facilitating Oxidation and Hydration Reactions | journal = Angew. Chem. Int. Ed. | volume = 49 | issue = 38 | pages = 6813–6816 | doi = 10.1002/anie.201002160 | pmid = 20602388 }}