Application of V2O5 Catalysts to Diesel Nox Emission Control

DeNOx catalysts consisting of V₂O₅-Cr₂O₃-TiO₂ and V₂O₅ -MoO₃-TiO₂ have been prepared by means of the coprecipitation method, characterized in terms of crystal structure using XRD and surface composition using XPS analysis. NOx reduction performance of urea on these catalysts has also been investigated using actual diesel engine exhaust gas. Consequently, It was found that these catalysts show high DeNOx activity and high reaction velocity above 300°C. With respect to the thermodynamic equilibrium for gaseous urea decomposition, it was considered that the DeNOx reaction might progress according to NH₃-SCR at temperatures above 300°C, but that the reaction would be controlled at temperatures below 300°C by decomposition of urea adsorbed on the catalyst, or by hydrolysis on the catalyst of adsorbed isocyanic acid derived from urea decomposition.