Selective Catalytic Removal of High Concentrations of NO x at Low Temperature.

Three vanadium-based catalysts were used to remove high concentrations of nitrogen oxides, and the catalysts' performance of de-NO_x and anti-H₂O under the high concentrations of NO_x were investigated. The V-Mo-W/TiO₂ catalysts were tested under 1500 mL/min gas flow (GHSV = 500 h⁻¹, 2.4% NO₂, 4.78% NH₃, 13% O₂, 4% H₂O, 5% CO₂) and characterized by BET, SEM, EDS, XRD, XPS, H₂-TPR, and NH₃-TPD; then, their physical and chemical properties were analyzed. The results showed that under the influence of H₂O, the NO_x conversion of the V-Mo-W/TiO₂ catalysts remained above 97% at 200–280 °C indicating that the catalysts had high catalytic activity and strong water resistance. The analysis of the characterization results showed that the larger specific surface area of the catalyst, the higher acid content, stronger redox ability, and higher V⁴⁺ and V³⁺ content were the reasons for the high NO_x conversion. The surface area decreased and the microstructure become smoother after the reaction, which may be caused by thermal sintering, but the overall morphology did not change. Comparing the H₂-TPR and NH₃-TPD of V_1.6Mo_1.7W_1.8/TiO₂ before and after NH₃-SCR reaction, it was found that the reduction peak and the intensity of the acid sites of the sample had not changed, which indicated that the catalyst had good anti-sintering performance and a long lifetime. This is significant for followup long-term engineering application experiments. [ABSTRACT FROM AUTHOR]