Copper ferrite supported gold nanoparticles as efficient and recyclable catalyst for liquid-phase ethanol oxidation

Copper-containing spinel-supported gold nanoparticle catalysts are optimized toward high activity and stability in liquid-phase aerobic oxidation Of aqueous bioethanol to acetic acid under mild hydrothermal conditions (3 MPa O-2, 140 degrees C). In this work, we investigate the structure-performance relationships of supported gold catalysts by changing the composition and calcination temperature of spine] supports to gain insight into the gold-support interaction. The support effect specially acts on the rate-controlling ethanol activation step, with ferrite-spinel outperforming aluminate and chromite-spinels, and the activity increasing with the copper content in the spinels. Moreover, support calcination at 700 degrees C results in the optimal Au/CuFe2O4 catalyst, which can be magnetically separated and reused at least five times. The improved reusability is likely attributed to the alloying between AuNPs and Cu-0 on the partially reduced CuFe2O4. The presence of negatively charged Au delta- and redox active Fe2+ species in the spent Au/CuFe2O4 catalyst points to a specific Au delta--Fe2+ synergy for the enhanced activation of O-2 and ethanol. With the help of negatively charged AuNPs, heterogeneous Fenton-like reaction is suggested to provide hydroxyl radicals for the C-H bond activation of ethanol. (C) 2017 Elsevier Inc. All rights reserved.