CuOx and WOx modified CeO2-TiO2 with various morphologies for the selective catalytic reduction of NOx with NH3

Abstract

CuOx and WOx modified CeO2-TiO2 (CeTi) with three various morphologies were fabricated and applied for selective catalytic reduction of NOx by NH3 (NH3-SCR). Catalytic performance showed that the loading of CuOx and WOx can enhance the low-temperature and high-temperature NH3-SCR activity of CuOx-WOx/CeO2-TiO2 (CuW/CT), respectively. CuOx-WOx/CeO2-TiO2 nanopolyhedrons (CuW/CT-NP), CuOx-WOx/CeO2-TiO2 nanorods (CuW/CT-NR) and CuOx-WOx/CeO2-TiO2 nanocubes (CuW/CT-NC) predominately exposed {111}, {110} and {100} crystal planes, respectively. The NH3-SCR performance indicated that CuW/CT-NP achieved the best NH3-SCR activity, excellent resistance to H2O&SO2 and the widest reaction temperature window with a full conversion temperature (T90) of 178 °C, much lower than that of CuW/CT-NR (210 °C) and CuW/CT-NC (273 °C). XPS, Raman, H2-TPR and NH3-TPD results confirmed that the redox and acidic properties of CuW/CT catalysts were closely related to the exposed facets of CeTi supports. The in situ DRIFTS results indicated that both NH3 and NOx adsorbed on the catalysts surface were active species. CuW/CT-NP exhibited stronger adsorption capacity for NOx and NH3 compared with CuW/CT-NR and CuW/CT-NC. A large number of active NH3 and nitrate species were formed on the surface of CuW/CT-NP, and the Langmuir Hinshelwood (L-H) pathway accelerated the NH3-SCR reaction, thereby enhancing the NH3-SCR performance.