DFT and experimental study on denitration mechanism over VPO/TiO2 catalyst.

A titanium dioxide supported VPO(VPO/TiO₂) catalyst for NH₃-SCR de-NO_x was prepared. The NH₃-SCR catalytic activity of VPO/TiO₂ was tested and a corresponding mechanism was investigated by Density Functional Theory and in situ FTIR spectra. The results showed that the catalytic activity of VPO/TiO₂ was the highest when the molar ratio of P to V was 1/5, weight percentage of active ingredient was 10 wt.% and calcination temperature was 400 °C. The de-NO_x efficiency of 0.1VP(1/5)O/TiO₂ calcined at 400 °C was above 98% at temperature range from 180 to 400 °C. The V₂P₂O₁₅H₁₂ cluster was constructed and the adsorption of NO and NH₃ on the active site of VPO/TiO₂ was investigated by density functional theory (DFT). The simulation results showed that NO could be chemisorbed on the O2 and O3 site of the V₂P₂O₁₅H₁₂ cluster, and the corresponding adsorption energy was − 74.95 kJ·mol⁻¹ and − 47.30 kJ·mol⁻¹ respectively. The adsorption energy of NH₃ adsorption on O1, O2 and O3 site is − 95.88 kJ·mol⁻¹, − 230.80 kJ·mol⁻¹ and − 78.45 kJ·mol⁻¹. Moreover, the electric charge transformation of H on O2 site is 0.589e, which is higher than that on O1 and O3 site. Accordingly, the NH₃-SCR de-NO_x reaction would occur more easily on the O2 site than on the O1 and O3 site. The simulated results and the in situ FTIR spectra showed that the reduction of NO by NH₃ over VPO/TiO₂ followed the E–R mechanism and L–H mechanism. [ABSTRACT FROM AUTHOR]