Use of Rh (III)-Heteropolymolybdate as Potential Catalysts for the Removal of Nitrates in Human Drinking Water: Synthesis, Characterisation and Catalytic Performance
2018
Jaworski, María A. | Bertolini, Guillermo R. | Cabello, Carmen I. | Siri, Guillermo J. | Casella, Mónica L.
The investigation and development of technologies to remediate water contaminated with NO₃⁻ are constantly increasing. An economically and potentially effective alternative is based on the catalytic hydrogenation of NO₃⁻ to N₂. With this objective, bimetallic RhMo₆ catalysts based on Anderson-type heteropolyanion (RhMo₆O₂₄H₆)³⁻ were prepared and characteri3ed in order to obtain well-defined bimetallic catalyst. The catalysts were supported on Al₂O₃ with different textural properties and on silica. The heteropolyanion-support interaction was analysed by temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). The differences obtained in activity and selectivity to the different products can be assigned to the different interaction between the RhMo₆ Anderson phase and the supports. The RhMo₆/G, (G: γ-Al₂O₃) system showed the best catalytic performance. This catalyst exhibited the lowest reduction temperature of Rh and Mo in the TPR assay and a Rh/Mo surface ratio similar to that of the original phase, as observed by XPS analysis. These studies allowed us to verify a synergic effect between Rh and Mo, through which Mo reducibility was promoted by the presence of the noble metal. The catalytic activity was favoured by the active sites generated from the Anderson phase. This fact was confirmed by comparing the activity of RhMo₆/G with that corresponding to a conventional catalyst prepared through successive impregnation of both Rh (III) and Mo (VI) salts.
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