Abstract
Mono metallic and bimetallic Pd (1 wt. %)–Au (3 wt. %) catalysts were prepared using two ceria supports doped with 1 wt. % Y2O3. Yttrium was added by impregnation or co-precipitation. The catalyst synthesis was carried out by deposition–precipitation method, with sequential deposition–precipitation of palladium over previously loaded gold in the case of the bimetallic samples. The obtained materials, characterized by X-ray powder diffraction (XRD), High resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and temperature programmed reduction (TPR) techniques, were tested in the complete benzene oxidation (CBO). The results of the characterization analyses and the catalytic performance pointed to a close relationship between structural, redox, and catalytic properties of mono and bimetallic catalysts. Among the monometallic systems, Pd catalysts were more active as compared to the corresponding Au catalysts. The bimetallic systems exhibited the best combustion activity. In particular, over Pd–Au supported on Y-impregnated ceria, 100% of benzene conversion towards total oxidation at the temperature of 150 °C was obtained. Comparison of surface sensitive XPS results of fresh and spent catalysts ascertained the redox character of the reaction.
Highlights
Volatile organic compounds (VOCs) are a major environmental hazard, being dangerous for human health because of their toxic nature as well as being ozone and smog precursors
In order to understand the reciprocal effect of each catalyst component, the catalytic behaviors in complete benzene oxidation (CBO) reaction of Au, Pd and Pd–Au catalysts supported on CeO2 and on Y-doped CeO2 were compared
Modification of the Y 3d spectra were not so sharp except for a slight increase in the Y 3d binding energy upon CBO. These X-ray photoelectron spectroscopy (XPS) results suggested the involvement of palladium oxide and, to a minor extent, of gold in the catalytic oxidation of benzene with the consequent reduction of the two noble metal species
Summary
Volatile organic compounds (VOCs) are a major environmental hazard, being dangerous for human health because of their toxic nature as well as being ozone and smog precursors. The catalytic behavior of gold and palladium catalysts supported on different oxides have been investigated in the complete benzene oxidation (CBO) [4,6,7]. The deposition of palladium on a Fe doped CeO2 supported gold catalyst allowed high CBO performance to be obtained [25]. Our team reported the positive effect of Y3+ modified ceria on the supported gold catalysts for the CO preferential oxidation reaction [30]. A recent investigation of the influence of the ceria Y-doping on the catalytic properties of supported gold catalysts in CBO reaction, established a beneficial effect of 1 wt. In order to understand the reciprocal effect of each catalyst component, the catalytic behaviors in CBO reaction of Au, Pd and Pd–Au catalysts supported on CeO2 and on Y-doped CeO2 were compared. The study aimed lowering the temperature for complete combustion of benzene, in order to reduce the operating cost of air pollution abatement processes
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