The Properties and SCR de-NO_x Application of Supported V₂O₅/TiO₂ Catalysts with Different Polymerization State of VO_x Species Controlled by the pH Value of Their Precursors

NO_x is the main pollutant in the air, which causes many harmful effects on society. The V₂O₅/TiO₂ catalysts are very important to reduce the NO_x from the heat engine plants and vehicle exhausts. However, various reasons will affect the performance of the catalysts. In this paper, the polymerization state of surface VO_x of supported V₂O₅/TiO₂ catalysts was controlled by changing the pH value of the impregnation precursor solutions, and the redox and acidity properties of the catalysts can be adjusted consequently. The Raman spectroscopy, ⁵¹V magic-angle spinning nuclear magnetic resonance (MAS NMR), H₂-temperature-programmed reduction (H₂-TPR), NH₃-temperature-programmed desorption (NH₃-TPD), NH₃-temperature-programmed oxidation (TPO) and ¹⁵NH₃-NO-O₂-temperature-programmed surface reaction (TPSR) were mainly used for the characterization and properties tests of the samples. Although all catalysts in this work had similar surface morphology and the same vanadium loading, the catalyst oxidability decreased while acidity increased with the increasing of VO_x polymerization, which causes the NO conversion increases with the increasing of VO_x polymerization below 300°C in selective catalytic reduction (SCR) de-NO_x reaction. This work will promote the advance in catalysis and anti-pollution fields for human and nature.