Structure and activity of Pd/V2O5/TiO2 catalysts in Wacker oxidation of ethylene

Barthos, Róbert and Hegyessy, András and Novodárszki, Gyula and Pászti, Zoltán and Valyon, József (2016) Structure and activity of Pd/V2O5/TiO2 catalysts in Wacker oxidation of ethylene. APPLIED CATALYSIS A-GENERAL, 531. pp. 96-105. ISSN 0926-860X

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Abstract

Studies reveal that V2O5 supported on TiO2 is more active in gas phase oxidation reactions by O2 than on Al2O3 or SiO2 support. Nevertheless, the Pd/V2O5/TiO2 catalyst was hardly studied in heterogeneous Wacker-oxidation. The present study concerns preparation of Pd/V2O5/TiO2 catalysts and activity of the catalysts in selective gas phase oxidation of ethylene by O2 in presence of water at atmospheric pressure and in the temperature range of 100-200 oC. The influence of palladium and vanadia loading and the partial pressures of the reactants on the yield of oxidation products (acetaldehyde and acetic acid) were examined. The surface-bound vanadia forms were identified by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), and FT-Raman spectroscopy. The best activities were achieved with catalysts, having near to monolayer vanadia coverage of the support. Time-on-stream catalytic tests and chemical analysis of the fresh and used catalysts proved the structural and catalytic stability of the Pd/V2O5/TiO2 preparations. It was shown that under the conditions of Wacker-oxidation primary product acetaldehyde could become further oxidized to CO2, whereas no consecutive oxidation of product acetic acid proceeded.

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