Inhibition Mechanism of H₂O on CO Oxidation Over CeMnO_x Catalyst in Iron Ore Sintering Flue Gas

The emission of CO in sintering flue gas contributes to environmental pollution and energy wastage. Achieving full oxidation of CO presents a viable strategy for elevating the sintering flue gas temperature by over 50°C, thereby significantly reducing energy consumption during the heating of flue gas in NH₃-SCR denitrification systems. In this work, MnCeOx catalysts were synthesized under various conditions, including different calcination temperatures, durations, and molar ratios. Their catalytic activity and resistance to H₂O were evaluated under simulated sintering flue gas conditions at different temperatures. Our findings indicated that the M₈C₁ catalyst exhibited exceptional activity, achieving CO conversion rates exceeding 95% within 125–250°C. However, the catalytic activity experienced a notable decline during the H₂O resistance test at 150°C, while remaining unaffected at 250°C. Investigating the inhibition mechanism of H₂O on CO oxidation at varying temperatures through H₂-TPR, O₂-TPD, and in situ DRIFTS. At lower temperatures (150°C), CO and O₂ adsorption on the catalyst surface led to the formation of CO₂, with O₂ adsorption exerting a more significant influence on activity, consistent with the Langmuir–Hinshelwood mechanism. Introduction of H₂O into the flue gas resulted in the formation of OH⁻, which competed with CO and O₂ for adsorption on the catalyst surface, thereby diminishing catalyst oxidation activity due to competitive adsorption hindering CO and O₂ adsorption. Conversely, at higher temperatures (250°C), the reaction process between CO and lattice oxygen to produce CO₂ followed the Mars-van Krevelen mechanism. Notably, at these temperatures, no adsorbed OH⁻ were detected on the catalyst surface, leaving the activity unaffected. Based on our research, employing the MnCeOx catalyst during the high-temperature stage in conjunction with the NH₃-SCR catalyst is recommended for enhanced CO oxidation efficiency in sintering flue gas treatment processes.