Selective oxidations
Sustainable pathways to the chemo-, regio- and stereoselective oxidation of fine chemicals
Contacts:
The oxidation of organic substrates leads to the production of major industrial valuable products, such as ketones, aldehydes, esters, carboxylic acids, alcohols, etc. Nevertheless, mainly in fine chemicals manufacture, oxidations are still carried out with huge stoichiometric amounts of conventional oxidants, such as chromium(VI) species, permanganate or organic peracids. Excessive quantities of toxic metals imply the unavoidable production of large amounts of toxic wastes that need proper disposal. Thanks to redox molecular sieves, it is possible to use oxidants that are economically and environmentally more sustainable. Oxidants that contain a high percentage of active oxygen and that give rise to harmless (or easily recyclable) side products are molecular oxygen, hydrogen peroxide, nitrous oxide and alkyl hydroperoxides (typically tert-butylhydroperoxide; TBHP).
For specific applications, where a chemo-, regio- and stereo-selective catalyst is required, tailored and specifically designed organometallic precursors are grafted or anchored onto inorganic oxide supports with controlled geometric, morphologic and textural properties (ordered mesoporous silica materials, nanostructured inorganic oxides, clays and layered solids). Novel heterogeneous catalysts for the oxidation of high added-value substrates (terpenes, flavours and fragrances, nutraceuticals, additives) are therefore obtained. In all these examples, a constant attention to the economic sustainability and to the industrial feasibility is paid.
One-pot epoxidation of alkenes by "in situ" formed cumyl hydroperoxide over bifunctional copper catalyst
Contacts:
Epoxides are versatile synthetic intermediates but actually their production routes overlook energy, atom efficiency and environmental concerns, therefore more affordable production pathways are constantly pursued. We studied the one-pot epoxidation of alkenes over a bifunctional alumina-supported copper catalyst (CuO/Al2O3), mediated by the in situ formation of cumyl hydroperoxide, generated by reaction between cumene and O2. The reaction (T=100 °C, pO2=1 bar), performed without the addition of any radical initiators, leaded to high conversion and selectivity with different substrates and in particular with methyl oleate in 6 h we obtained the 84% of yield while the catalyst showed a good stability and reusability and it could be used at least 3 times, affording only a slight decrease in its catalytic performances.
