Improving the H2O/SO2 tolerance of Nd-modified Mn-Fe/FA through tailing the micro-environment of active sites in low-temperature NH3-SCR

The development of low-temperature NH3-SCR catalysts with high H2O/SO2 tolerance using coal fly ash, a solid waste was produced from coal combustion, as a carrier remains a significant challenge. Herein, we constructed an Nd-Mn-Fe/FA catalyst utilizing coal fly ash as a supporter material. The addition of Nd effectively adjusted the micro-environment of active sites, leading to improved resistance and de-NOx abilities. The NOx conversion maintained at 98 % even with the addition of H2O (5 vol% or 10 vol%) or SO2 (20 ppm) at 150 degrees C for 4 h, and the NOx conversion only decreased slightly from 98 % to 95 % when H2O (5 vol%) and SO2 (20 ppm) were cointroduced at 150 degrees C for 4 h. Moreover, the Nd-Mn-Fe/FA catalyst exhibited outstanding low-temperature NH3-SCR activity, achieving over 90 % NOx conversion in the temperature range of 80-200 degrees C. This is attributed to the addition of Nd, which increased the specific surface area and consequently reduced the apparent activation energies of the catalyst. Importantly, the addition of Nd altered the NH3-SCR pathway from both EleyRideal (E-R) and Langmuir-Hinshelwood (L-H) to primarily E-R. This work highlights the importance of incorporating Nd into coal fly ash (a solid waste) to enhance low-temperature de-NOx and H2O/SO2 resistance abilities, as well as providing a new way to treat and utilize the coal fly ash and mitigate the release of NOx.