Effects of SO2 on the low temperature selective catalytic reduction of NO by NH3 over CeO2-V2O5-WO3/TiO2 catalysts

The CeO2-V2O5-WO3/TiO2 (CeO2-VWT) catalysts were prepared by one-step and two-step impregnation methods. The effects of different loading of CeO2 and different preparation methods on De-NOx\ activity of catalysts had been investigated. CeO2 helped to improve the De-NOx activity and sulfur resistance. The optimal loading of CeO2 was 3% with the De-NOx efficiency reached 89.9% at 140(circle)C. The results showed that the De-NOx activity of 3% CeO2-VWTcatalysts by one-step method was the same as two-step method basically and reached the level of industrial applications, the N-2 selectivity of catalysts was more than 99.2% between 110(circle)C and 320(circle)C. In addition, CeO2 promoted the oxidation of NO to NO2, which adsorbed on the Lewis acid site (V5+-O) to form V5+-NO3 and inspired the fast SCR reaction. Not only the thermal stability but also the De-NOx activity of catalysts decreased with excess CeO2 competed with V2O5. Characterizations of catalysts were carried out by XRF, BET, XRD, TG and FT-IR. BETshowed that the specific surface area of catalysts decreased with the loading of CeO2 increased, the active components content and specific surface area of catalysts decreased slightly after entering SO2. Ammonium sulfate species were formed in poisoned catalyst which had been investigated by XRF, BET, TG and FT-IR. The largest loss rate of weight fraction was 0.024%C-circle (1) C (1) at 380(circle)C-390(circle)C, which was in accordance with the decomposition temperature of NH4HSO4 and (NH4)(2)SO4.