Unveiling the traits of rare earth metal (RM)-substituted bimetallic Ce0.5RM0.5V1O4 phases to activate selective NH3 oxidation and NOx reduction

Abstract

V2O5 contains V5+ accessible to NOx/NH3, thus having partial success in producing N-2 via selective NOx reduction (SCR) and NH3 oxidation (SCO). V2O5, however, can be advanced by structural modification with rare-earth metal (RM) to form vanadate (RM1V1O4), wherein Lewis acidity of open V5+ is regulated by the type of RM along with the change in Bronsted acidity/redox character. Herein, TiO2-supported Ce1V1O4 served as adaptable platform, where half of Ce was replaced by RM (Tb, Er, or Yb) to form Ce0.5RM0.5V1O4 catalysts. The promotive effect anticipated by RM substitution for Ce0.5RM0.5V1O4 was insignificant at low temperatures. Conversely, high temperatures tuned the property of Ce0.5RM0.5V1O4 desirably. Ce0.5RM0.5V1O4 possessed the greatest Lewis acidity/redox feature, thus revealing the best performance in SCR/SCO at elevated temperatures. Hydro-thermal aging (HT) of the catalysts was repercussive to their properties to some extents and altered the kind of major surface sites for SCR/SCO. Bronsted acidity/redox trait primarily directed low-temperature SCR performance of Ce0.5RM0.5V1O4 (HT), yet, were the greatest in Ce0.5Er0.5V1O4 (HT). Meanwhile, Lewis acidity of Ce0.5RM0.5V1O4 (HT) dominated high-temperature SCR/SCO performance and again was the most desired in Ce0.5Er0.5V1O4 (HT). This paper demonstrated the vitality of RM innate to Ce0.5RM0.5V1O4 for accelerating SCR/SCO exposed to periodic HT.