Effect of Water Vapor on Low Temperature SCR Performances over Cu and Mn-based Catalysts: A Comparison Study

In this study, the commonly used Cu or Mn-based low-temperature SCR catalysts were employed to investigate their different reaction behaviors in the presence of high-content water vapor. Experimental results reveal that CuCeTi sample possesses superior water resistance at low temperature compared with MnCeTi catalyst. Upon the introduction of water vapor, both catalysts exhibit a quick loss in deNOx efficiency, while that is more pronounced on MnCeTi sample. In addition, unlike CuCeTi sample, MnCeTi catalyst also shows a gradual deactivation tendency after initial quick activity loss. Characterization and simulation results indicate that H2O is more easily adsorbed and dissociated on MnCeTi catalyst, showing stronger suppression on NH3 adsorption, causing more serious initial deactivation. Furthermore, more abundant hydroxyl groups derived from dissociative adsorption of water on MnCeTi catalyst will lead to more NH4NO3 deposition and the decrease in redox capacity. This is the main reason of gradual deactivation of MnCeTi catalyst at high-content water vapor. Such findings could pave a new way for development of highly efficient SCR catalysts with good water resistance for real application.