Inhibitory effect and mechanism of varying water vapor content on a monolithic low-temperature NH3-selective catalytic reduction catalyst

The development of low-temperature selective catalytic reduction (SCR) denitrification catalysts suitable for high-moisture flue gas environments remains a significant challenge, with the research gap regarding monolithic catalysts particularly hindering practical applications of this technology. In this study, the prepared Fe-Mn-Ce/Al 2 O 3 monolithic catalyst maintained a denitrification efficiency of 73.6 % even under 16 vol% water vapor conditions, meeting industrial requirements. This study reveals that the influence of H 2 O on the denitrification reaction exhibits a distinct concentration dependence: at low water content (< 8 vol%), inhibition primarily occurs through competitive adsorption with reactants for active sites. At high water content (> 8 vol%), H 2 O significantly reduces the surface active oxygen concentration, leading to impeded re-oxidation of the metal active sites, which consequently results in a decline in redox cycle efficiency. This is considered the primary reason for the reduction in denitrification performance under high-humidity conditions. This study provides an important theoretical foundation for the development of low-temperature denitrification catalysts suitable for high-moisture industrial flue gas conditions.