Autori: Mathew D. Hughes; Yi-Jun Xu; Patrick Jenkins; Paul McMorn; Philip Landon; Dan I. Enache; Albert F. Carley; Gary A. Attard; Graham J. Hutchings; Frank King; E. Hugh Stitt; Peter Johnston; Ken Griffin; Christopher J. Kiely

Editorial: Nature, 437(7062), p.1132-1135, 2005.

Rezumat:

Oxidation is an important method for the synthesis of chemical
intermediates in the manufacture of high-tonnage commodities,
high-value fine chemicals, agrochemicals and pharmaceuticals:
but oxidations are often inefficient1. The introduction of catalytic
systems using oxygen from air is preferred for ‘green’ processing2.
Gold catalysis is now showing potential in selective redox
processes3-6, particularly for alcohol oxidation7-10 and the direct
synthesis of hydrogen peroxide11,12. However, a major challenge
that persists is the synthesis of an epoxide by the direct electrophilic
addition of oxygen to an alkene13. Although ethene is
epoxidized efficiently using molecular oxygen with silver catalysts
in a large-scale industrial process14, this is unique because
higher alkenes can only be effectively epoxidized using hydrogen
peroxide15-17, hydroperoxides16 or stoichiometric oxygen donors.
Here we show that nanocrystalline gold catalysts can provide
tunable active catalysts for the oxidation of alkenes using air, with
exceptionally high selectivity to partial oxidation products
(,98%) and significant conversions. Our finding significantly
extends the discovery by Haruta18,19 that nanocrystalline gold
can epoxidize alkenes when hydrogen is used to activate the
molecular oxygen; in our case, no sacrificial reductant is needed.
We anticipate that our finding will initiate attempts to understand
more fully the mechanism of oxygen activation at gold surfaces,
which might lead to commercial exploitation of the high redox
activity of gold nanocrystals.

Cuvinte cheie: no key words for Nature publications

URL: http://www.nature.com/nature/journal/v437/n7062/pdf/nature04190.pdf