Abstract
New MoO3 or WO3 modified CeO2-ZrO2 aerogel catalysts were elaborated using the sol gel method combined to supercritical drying for the NO-SCR by NH3 in excess of O2. XRD, N2-Physisorption, NH3-TPD, H2-TPR and DRUV-Vis spectroscopy were used to analyse the samples. The results reveal that all the aerogel powders (ZrO2, CeO2-ZrO2, MoO3-ZrO2, WO3-ZrO2, MoO3-CeO2-ZrO2 and WO3-CeO2-ZrO2), calcined at 500°C, are nanostructured and mesoporous materials, developing essentially the diffraction peaks of the ZrO2 tetragonal phase, which was stabilized by the presence of cerium. Ce, Mo and W species were found highly dispersed on the zirconia surface, their nature and the diverse interactions developed between them affect the crystallites size of ZrO2, acidity, reducibility, surface oxygen mobility of catalysts and influence extremely their SCR activity. Higher NO-SCR performances are obtained, between 200 and 500°C, over the new ternary MoO3-CeO2-ZrO2 and WO3-CeO2-ZrO2 catalysts compared to corresponding binary systems (CeO2-ZrO2, MoO3-ZrO2 and WO3-ZrO2). This discloses a synergism in the NO-SCR related to the existence of strong interactions Ce↔Mo and Ce↔W. Interestingly, above 90 % NO conversions into essentially N2 (≥ 97 %) are achieved between 350 and 500°C over the most efficient MoO3-CeO2-ZrO2 ternary catalyst.
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