Toluene oxidation on three ceria catalysts, CeO2, VOx/CeO2 and Au/CeO2, was investigated by an operando Raman-online FTIR reactor cell. Oxygen vacancies on ceria, were the preferred sites for vanadium and gold deposition. On the surface of catalysts, vanadium existed as V5+, while most of the gold was in Au+ state and roughly a third of ceria was in the reduced Ce3+ state. Au/CeO2 and CeO2 catalysts were more active and selective towards complete oxidation of toluene than VOx/CeO2 catalyst. The the presence of peroxide O22-ads species is apparent on Au/CeO2 and CeO2 catalysts, where toluene adsorbs parallel to the surface via π-bonding. While, superoxide species are apparent on VOx/CeO2 catalyst, where toluene adsorbed head-on through σ-bonding via the methyl group forming carbenium ions on vanadia Brønsted acid sites. VOx/CeO2 catalyst produced benzaldehyde as partial oxidation byproduct and CO from incomplete combustion. The nature of the active sites, the adsorption configuration of the toluene molecule, and the reactive oxygen species dictate the catalytic activity and reaction pathway resulting in the contrasting reaction conversion and selectivity for the CeO2, VOx/CeO2 and Au/CeO2 catalysts. The use of pororous carbon material, is explored to handle moisture. ACKNOWLEDGEMENTS. This work was financial supported by the Spanish Ministry [CTQ2014-57578-R]; NSFC/RGC Joint Research Scheme [N-HKUST626/13]. The authors express their gratitude to Dr. Laura Pascual, Ms. Mei Leng Liu and Mr. Nick K C Ho for technical supports. Also, thanks to the Oversea Research Award from School of Engineering, HKUST for supporting the exchange program at the ICP-CSIC, in Spain.

Operando Raman-online FTIR investigation on the role of vanadium and gold doping on ceria-based catalysts for toluene elimination

255th National Meeting (2018)

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