New insight into alkali resistance and low temperature activation on vanadia-titania catalysts for selective catalytic reduction of NO.

Graphical abstract Highlights • The SCR activity and alkali resistance was tested over a series of vanadia-titania catalysts. • V 4 /Ti catalyst displayed the best performance after doping with potassium. • V4+ species were sensitive to be affected by alkali metals. • Acidity played a critical role in the poisoned catalysts. • Competition of NH 3 oxidation mainly caused the deactivation with V > 4%. Abstract A series of vanadia-titania catalysts with different vanadia loadings for the selective catalytic reduction (SCR) of NO by ammonia was prepared via incipient impregnation method. The alkali resistance and SCR activity at low temperature has been investigated on the prepared catalysts. Increasing the vanadia loading from 1% to 10%, the NO removal efficiency of the catalysts gained a 70% growth at 200 °C. With the increase of the vanadia loading, the high loading vanadia-titania catalysts exhibited higher ratio of V5+/(V4++V5+), which enhanced the oxidation of NH 3 at high temperatures and also improved the standard SCR performance at low temperature. After doping with potassium, V 4 /Ti catalyst (V 2 O 5 = 4 wt%) displayed the best performance over which 80% initial activity was retained from 300 °C to 400 °C. More acid sites and active vanadium species were retained in the high loading vanadia-titania catalysts, which made them exhibit better low temperature alkali resistance. However, when vanadia content was higher than 4%, the competition of NH 3 oxidation severely deactivated the catalytic activity above 250 °C. Additionally, in the presence of SO 2 and H 2 O the SCR performance of the high loading vanadia-titania catalysts were also studied in order to investigate the influence of the actual working conditions. [ABSTRACT FROM AUTHOR]