Improvement of Ce[sbnd]Nb doping on low-temperature catalytic activity of a VOx-based catalyst for NH3–SCR reaction

Abstract

A series of VxCeNbTi catalysts were prepared using a wet impregnation method for selective catalytic reduction (SCR) of NO by NH3. The influence of CeNb addition to VTi was investigated in terms of active sites and acidity. The correlation between surface properties, catalyst structure, and performance with the addition of Ce and/or Nb was demonstrated. The composition of VCeNbTi species, surface acid properties, and redox behavior were studied. Results showed that the addition of 2CeNb to VTi increased NH3 adsorption, and brought about positive changes in Brönsted acid sites and composition of surface species. Nbn+ mainly existed as typical Nb2O5 species, forming abundant acid sites and defects on the catalyst surface, closely related to the distribution of VOx species which varied with ceria content. The presence of 2CeNb induced electron redistribution, promoting oxygen defects and reactive oxygen species formation due to the occupancy of high Vn+ (n = 4, 3). The increased proportion of Vn+ (n = 4, 3) improved catalytic activity by generating active groups on the catalyst surface. The introduction of 2CeNb enhanced SCR performance with increased NO2 generation. V2CeNbTi exhibited improved resistance in the presence of SO2/H2O, crucial for high-performance and durable catalysis.