Iron-containing tailings catalyst modified by Mn for SCR of NO with NH3 at low temperature: Study of carrier treatment and calcination temperature

Abstract

The development of cost-effective low temperature selective catalytic reduction (NH3-SCR) catalysts for nitrogen oxides is a major challenge. To this end, a low-cost rare earth tailings catalyst modified by Mn was successfully synthesized by the impregnation method using rare earth tailings as raw materials. The iron-containing tailings catalyst modified by Mn exhibited high NH3 SCR activity with high N2 selectivity at low temperature range (150–200 ℃). The H2SO4 modification resulted in the weakening of the Fe-O bonds on the catalyst, thereby producing the active component, iron sulfate salt. The coordination occupancy of Brønsted acid sites is increased, thereby facilitating electron transfer and redox cycling of SCR. Furthermore, by modulating the calcination temperature, the synergistic effect of Fe and Mn is augmented, resulting in the generation of a substantial number of Mn-Fe composite oxides, which is conducive to the enhancement of NH3 adsorption and activation on the catalyst. The formation of additional Brønsted acids was identified as a primary factor influencing the enhancement of N2 selectivity in the catalyst. The catalytic process followed both the E-R and L-H mechanisms on the catalyst. The Iron-containing tailings catalyst modified by Mn represents a cost-effective and resource-conserving alternative. The provision of high denitrification efficiency, coupled with the capacity to address the issue of low N2 selectivity, offers a sustainable and low-carbon solution for the industrial reduction of NOx.