Comparative Effects of Ce, Co, or W Dopants on the Catalytic Performance of FeMnTiOx Catalysts for Low-Temperature NH3-SCR of NO.

To clarify the role of metal dopants in low-temperature NH3-SCR of NO, FeMnTiOx catalysts were synthesized by coprecipitation and separately modified with Ce, Co, or W. The catalysts were evaluated for NO conversion, separate O2/H2O switching response and dry-feed time-on-stream stability and characterized by XRD, SEM, N2 adsorption-desorption, XPS, H2-TPR and NH3-TPD. Ce doping at Ce/Mn = 0.3 suppressed TiO2 crystallization, increased the BET surface area from 136 to 231 m2 g-1 and the pore volume from 0.19 to 0.58 cm3 g-1, raised the Mn4+/Mn3+ ratio from 0.70 to 1.25, and increased the medium-strong-acid relative peak area from 555.4 to 1293.2 a.u. FeMnCe0.3TiOx maintained at least 90% NO conversion from 140 to 360 °C, gave 75% conversion at 400 °C, and averaged 97.4% during a 40 h dry-feed test at 350 °C. The results show that the superior Ce-modified catalyst arises from the combined regulation of texture, surface redox balance and acidity.