Selective Catalytic Reduction Of NO_x By H₂Over Pt-W（Mo）/TiO₂Catalysts

Effects of added WO3and MoO3on the catalytic performance of Pt/TiO2catalyst for the selective catalytic reduction of NOX by H2(H2-SCR) have been investigated, respectively. In this research a series of Pt/TiO2、PtW/TiO2and PtMo/Ti02catalysts were developed and characterized by temperature-programmed reduction of H2(H2-TPR), N2physisorption (BET), X-ray diffraction (XRD), temperature-programmed desorption of NOx (NOx-TPD) and In situ DRIFTS.Activity test results showed that a PtW/TiO2catalyst with a Pt loading of0.5wt.%and a WO3content of2wt.%showed the highest catalytic performance at low temperatures(100-175℃) with a maximum deNOx conversion obtained at125℃. PtMo/TiO2catalyst with a Pt loading of0.5wt.%and a MoO3content of2wt.%also exhibited the highest performance at low temperatures(10Q·175℃), and a maximum deNOx conversion was obtained at150℃. Hydrothermal pretreatment can lead to the further improvement of the catalytic performance of PtW/TiO2and PtMo/TiO2catalysts.XRD results revealed that the introduction of WO3and MoO3facilitates the crystallization of Pt oxides and results in an interaction with TiO2. H2-TPR showed that the reduction temperature of PtOx becomes lower due to the added promoter, which is responsible for the improvement of catalytic activity at low temperature.In situ DRIFTS results showed that introduction of WO3and MoO3can promote the dismutation of NO2which produce NO+on Pt and nitrate species; Meanwhile, NO+O2-H2transient and NO+O2+H2steady IR revealed that nitrogen species and NH4+showed reaction activity. Considering the lower activity of NH4+we concluded that the main reason for the increase of catalyst activity after introducing WO3and MoO3at low temperature is due to more types of nitrogen-containing species formed.