Au/CeO2-ZnO/Al2O3 as Versatile Catalysts for Oxidation Reactions: Application in Gas/Liquid Environmental Processes.

Cristina Megías-Sayago,Tomas Ramirez Reina,Jose A Odriozola,Svetlana Ivanova

doi:10.3389/fchem.2019.00504

Cristina Megías-Sayago, Tomas Ramirez Reina + Show 2 more

Open Access

https://doi.org/10.3389/fchem.2019.00504

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Abstract

The present work showcases the versatility of nanogold systems supported on Zn-doped ceria when applied in two important environmental processes, the total CO oxidation, and the liquid phase oxidation of glucose to gluconic acid. In the CO oxidation the suitability of these materials is clearly demonstrated achieving full conversions even at sub-ambient conditions. Regarding the glucose oxidation our materials display high conversion values (always over 50%) and very importantly full or almost full selectivity toward gluconic acid—an added value platform chemical in the context of biomass upgrading routes. The key factors controlling the successful performance on both reactions are carefully discussed and compared to previous studies in literature. To our knowledge this is one of the very few works in catalysis by gold combining liquid and gas phase reactions and represents a step forward in the flexible behavior of nano gold catalysts.

Highlights

The strategy to develop efficient gold-based catalysts for a specific reaction involves a careful control of the synthesis parameters as well as the proper support selection to disperse gold nanoparticles
The Ce-Zn solid solution is hard to obtain according to the Hume-Rothery rules (William and Hashemi, 2006), it was reported that an epitaxial interaction between both zinc and cerium oxides may create preferential sites for gold deposition in the oxides interface leading to a high gold dispersion and improved catalytic activity (Laguna et al, 2011)
Cerium loadings are close to the nominal value (15 wt.%), contrary to the amount of zinc oxide in the doped systems, which resulted to be ∼50% of the intended value

Summary

Introduction

The strategy to develop efficient gold-based catalysts for a specific reaction involves a careful control of the synthesis parameters as well as the proper support selection to disperse gold nanoparticles. The selective glucose oxidation has been carried out over both unsupported (Comotti et al, 2004; Beltrame et al, 2006) and supported (Biella et al, 2002; Ishida et al, 2008) gold catalysts with good results in terms of activity and selectivity. Gold has been deposited over a homemade CeO2/Al2O3 support doped with small amounts of Zn (within the 0–2 wt.% range), targeting a complete Ce-M solid solution formation and generation of oxygen vacancies on the ceria lattice.

Results

Conclusion