Antimony modification of VO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si71.svg" display="inline" id="d1e571"><mml:msub><mml:mrow/><mml:mrow><mml:mtext>x</mml:mtext></mml:mrow></mml:msub></mml:math>/TiO2 NH3-SCR catalysts and the effect of thermal aging
Alexander Nellessen, Roberta Villamaina, Andreas Schaefer, Agnes Raj, Andrew D. Newman, Anna Martinelli, Per‐Anders Carlsson
Abstract
Titanium oxide supported vanadium oxide (VO x /TiO 2 ) remains an important material for catalytic reduction of NO x emissions, but to address future air pollution scenarios, its thermal stability must be improved without sacrificing its catalytic SCR activity. In this study, antimony oxide modified VO x /TiO 2 catalysts were prepared via incipient wetness impregnation and investigated both in fresh state and after thermal stress at 580 °C in static air for 100 h, reflecting a common aging protocol in automotive applications. Characterization of the fresh and aged catalysts was performed by nitrogen physisorption, ammonia temperature-programmed desorption, Raman and in situ infrared spectroscopy and compared with the bare TiO 2 support and an unmodified VO x /TiO 2 catalyst as references. The addition of antimony oxide stabilizes the anatase TiO 2 phase and shows an inherent standard SCR activity even in the absence of vanadium. The modification of VO x /TiO 2 catalysts by antimony oxide reveal an improved SCR performance after aging despite the formation of V 2 O 5 and rutile at a high V loading. This improvement may be related to enhanced redox properties that are influenced by the V/Sb molar ratio, with the catalyst having a molar V/Sb ratio of 1.2 showing particularly notable activity after aging. Variations in the impregnation sequence have shown that co-impregnation of both components in fresh state is the most favorable synthesis route in terms of standard SCR activity, although the catalytic properties converge after aging. Further, the modification with antimony oxide resulted in a significantly reduced N 2 O formation, indicating improved selectivity toward the desired reaction. • Sb modification increases thermal stability of titania and preserves VO x dispersion. • SCR activity for Sb-modified VO x /TiO 2 increases upon thermal treatment • SCR activity and catalyst stability depends on V/Sb molar ratio. • Impregnation sequence affects SCR activity for fresh but not for aged catalysts