Effect of cerium-zirconium oxide-loaded red mud on the selective catalytic reduction of NO in downhole diesel vehicle exhaust

Red mud (RM), an iron oxide-rich solid waste, shows potential as a catalyst for selective catalytic reduction in denitrification processes. This study investigates the catalytic performance and mechanism of metal-modified RM in reducing NO from diesel vehicle exhaust. Acid-washed RM catalysts were impregnated with varying ratios of cerium (Ce) and zirconium (Zr). Our findings revealed that doping with Ce and Zr significantly enhances the denitrification activity at medium and low temperatures, highlighting the promising applicability of these elements as effective modification additives. The optimal performance was observed with a Ce:Zr loading ratio of 1:1, achieving 85% NO conversion at 250 °C. This conversion remained above 80% up to 400 °C, with a maximum of 92% NO conversion at 325 °C, thereby significantly widening the temperature window. Additionally, in-situ DRIFTS analysis revealed that the reaction process followed both the Eley-Rideal and Langmuir-Hinshelwood mechanisms.