Complex nitrogen modified promotion on vanadium phosphorus oxide catalysts with amorphous phases for low-temperature NH3-SCR of NOx.

Herein, this work used n-butylamine addition and NH3 atmosphere activation to optimize a vanadium phosphorus oxide catalyst. By comparing the low-temperature NH3-SCR activity, complex nitrogen modified samples (VPO-2B-NH3) performed best (> 90 % at 200-270 °C). XRD, Raman, and HRTEM results revealed a transition from the VOPO4 phase to the amorphous phase after the n-butylamine addition. Complex nitrogen modification increased the specific surface area, surface acidity, enrichment of surface oxygen vacancies, and the ratios of V4+/(V4++ V5+) and Oads/(Oads + Olatt). In addition, the in-situ DRIFTs results indicated that the prepared catalyst simultaneously followed the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms. Complex nitrogen modification was used to improve NH3-SCR performance by accelerating consumption of surface NH3 (on Lewis acid sites) and NO2 species and decreasing the deposition of these species after the sustained reaction. This rationally elucidates the effect of complex nitrogen modification on the stability of the vanadium phosphorus oxide catalyst.