Simple solvent-free preparation of dispersed composites and their application as catalysts in oxidation and hydrocarboxylation of cyclohexane. (September 2017)

• Record Type: Journal Article
• Authors: Alegria, Elisabete C.B.A.; Fontolan, Emmanuele; Ribeiro, Ana P.C.; Kopylovich, Maximilian N.; Domingos, Catarina; Ferraria, Ana M.; Bertani, Roberta; Botelho do Rego, Ana M.; Pombeiro, Armando J.L.
• Is Part Of: Materials today chemistry. Volume 5(2017)
• Page Start: 52
• Page End: 62
• Publication Date: 2017-09
• Subjects: Mechanochemical -- Ball-milling -- Composites -- One-pot oxidation -- Hydrocarboxylation -- Cyclohexane; Chemistry -- Periodicals; Materials -- Research -- Periodicals; Materials science -- Periodicals; Chemistry; Materials -- Research; Electronic journals; Periodicals; 660.282
• DOI: 10.1016/j.mtchem.2017.07.002
• Languages: English
• ISSNs: 2468-5194

Abstract

Abstract: A simple and clean mechanochemical synthesis at room temperature was employed to prepare CuO-Fe2 O3 -CoCl2 (100 nm scale), MoO3 -V2 O5, CuO-CoCl2, Fe2 O3 -CoCl2, CuO-V2 O5, Cu(CH3 COO)2 -V2 O5, Cu(CH3 COO)2 -MoO3 (1–100 μm scale) 3 d metal based dispersed composites with different ratios of components using simple metal salts/oxides and multiwalled carbon nanotubes ( CNT ) or graphene oxide ( GO ) additives (CoCl2 - CNT, CoCl2 - GO ). The thus prepared composite materials were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), field emission gun scanning electron microscopy (FEGSEM), energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). XPS analysis revealed no metal redox change upon ball milling treatment, which however promotes metal hydroxylation. The catalytic activity of the prepared composites in the heterogeneous low power microwave-assisted oxidation of cyclohexane with aq. H2 O2 at 30 °C was notorious with yields up to 31% and selectivity up to 94% towards cyclohexanol (upon treatment with PPh3 ) for the CuO-CoCl2 -based material. The hydrocarboxylation of cyclohexane with CO, water and K2 S2 O8 to produce cyclohexanecarboxylic acid bearing one more carbon atom at 60 °C is achieved with yields up to 17% for the reaction performed in the presence of the CuO-CoCl2 catalyst. The clean CuO-CoCl2 (1:2) catalyst preparation and the catalytic reaction (oxidation of cyclohexane) can be achieved in one-pot at low temperature, without any added organic solvent, and by using exclusively the mechanochemical energy input, with a marked 23% yield at 30 °C. Graphical abstract: Highlights: A simple and clean mechanochemical synthesis of dispersed composites. No redox transformations within the dispersed materials upon their ball milling synthesis. Metal hydroxylation induced by ball-milling. Notorious catalytic efficiency in the oxidation and hydrocarboxylation of cyclohexane. Synthesis and catalytic reaction in one pot with exclusive mechanochemical energy input.