Antimony modification of VOx/TiO2 NH3-SCR catalysts and the effect of thermal aging

Journal article, 2025

Titanium oxide supported vanadium oxide (VOx/TiO2) remains an important material for catalytic reduction of NOx 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 VOx/TiO2 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 TiO2 support and an unmodified VOx/TiO2 catalyst as references. The addition of antimony oxide stabilizes the anatase TiO2 phase and shows an inherent standard SCR activity even in the absence of vanadium. The modification of VOx/TiO2 catalysts by antimony oxide reveal an improved SCR performance after aging despite the formation of V2O5 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 N2O formation, indicating improved selectivity toward the desired reaction.