Effect of MoO on vanadium based catalysts for the selective catalytic reduction of NO with NH at low temperature.

The selective catalytic reduction (SCR) activities of the MoO doped V/WTi catalysts prepared by the incipient wetness impregnation method at low temperature were investigated. The results showed that the addition of MoO could enhance the NO conversion at low temperature and the best SCR activity was obtained when the dosage of MoO reached 5wt.%. The NH-TPD and DRIFTS experiments indicated that the addition of MoO changed the type and number of acid sites on the surface of catalysts and reaction activities of acid sites were altered at the same time. The redox capacity and amount of active oxygen species got improved for V3Mo5/WTi catalyst, which could be confirmed by the H-TPR and transient response experiments. Water vapor inhibited the NO conversion at low temperature. Deposition of ammonium sulfate or bisulfate might be main reason for the loss of catalytic activity in the presence of SO at low temperature. Choosing the suitable NH/NO ratio and elevation of reaction temperature both could weaken the influence of SO on the SCR activity of the V3Mo5/WTi catalyst. Thermal treatment of the deactivated catalyst at 350°C could get the low temperature activity recovered. The decrease of GHSV improved the deNO efficiency at low temperature and we speculated that the rational technological process and operation parameters could contribute to the application of this kind of catalysts in real industrial environment.