Excellent low-temperature NH3-SCR of NO activity and resistance to H2O and SO2 over WaCeOx (a = 0.06, 0.12, 0.18, 0.24) catalysts: Key role of acidity derived from tungsten addition

Bimetallic WaCeOx (a = 0.06, 0.12, 0.18, 0.24) catalysts were synthesized for selective catalytic reduction of NOx with NH3 (NH3-SCR). The influences of W on structure, activity and surface properties were investigated by XRF, XRD, Raman, TEM, N2 adsorption-desorption, H2-TPR, O2/NH3/SO2-TPD, XPS, and in-situ DRIFTS. The characterization results show that the W/Ce ratio has a great effect on the NH3-SCR activity. The different catalytic activities of WaCeOx are mainly attributed to the acidity change, especially the increase of B-acid content plays a major role in enhancing low temperature activity. W0.18CeOx exhibits excellent low-temperature NH3-SCR activity, SO2/H2O resistance and N2 selectivity with a broad activity window (190–490 °C) with 5%H2O. Moreover, good activity window (235–460 °C) can be maintained even the catalyst treated with 5% H2O at 800 °C for 12 h, showing especial hydrothermal stability. Thus, it can be summarized that W0.18CeOx is regarded as outstanding catalyst for low-temperature NH3-SCR of NO.