Characterization of WMnCeTiOx catalysts prepared by different methods for the selective reduction of NO with NH3

Abstract

In this work, WMnCeTiO_x catalysts were prepared by three methods: coprecipitation (CP), deposition precipitation (DP), and sol–gel (SG). The effects of the preparation methods on the performance of the selective catalytic reduction of NO_x with NH₃ at 160–360 °C have been investigated systematically. XRD, BET, XPS, H₂-TPR, NH₃-TPD and in situ DRIFTS were used to characterize the physicochemical properties of the prepared WMnCeTiO_x catalysts. The results showed that WMnCeTiO_x catalysts prepared by CP and DP methods exhibited much better NH₃-SCR performance in a temperature range of 160–300 °C than that prepared by the SG method. Moreover, the WMnCeTiO_x catalyst prepared by the CP method exhibited a superior SO₂ and H₂O tolerance compared with those prepared by the DP and SG methods. According to characterization results, the excellent performance of the WMnCeTiO_x(CP) catalyst could be ascribed to its highly dispersed active components, larger surface area, higher concentrations of Mn⁴⁺ and surface chemisorbed oxygen, more surface acid sites, stronger reduction capacity and better adsorption capacity for NH₃ and NO. The in situ DRIFTS results indicated that the NH₃-SCR reaction on all the prepared WMnCeTiO_x catalysts obeyed both Langmuir–Hinshelwood and Eley–Rideal mechanisms.