Mechanism of NO Abatement via CO+NH 3 Synergistic Coupling over Na- and K-Poisoned Fe-Mn/AC Catalysts

The presence of sodium (Na) and potassium (K)in sintering flue gas can severely inhibit the activity of Fe-Mn/AC catalysts during the selective catalytic reduction (SCR) of NO via CO + NH 3 coupling. This study investigated the individual and synergistic poisoning effects of Na and K on the physicochemical properties and performance of Fe-Mn/AC catalysts. The results revealed that under conditions of 150℃–300℃ and 9% O 2 , Na- and K-poisoned Fe-Mn/AC catalysts exhibited decreased NO conversion and a corresponding decline in N 2 selectivity. The degree of deactivation followed the order 0.05Na+0.05K-3.5Fe7.0Mn/AC > 0.1K-3.5Fe-7.0Mn/AC > 0.1Na-3.5Fe-7.0Mn/AC. Comprehensive characterization (SEM-EDS, BET, XRD, XPS, and Fourier-transform infrared spectroscopy) revealed that Na and K poisoning caused surface roughening, pore blockage, and agglomeration of active components, resulting in a significant reduction in specific surface area (from 583 m 2 /g to 510 m 2 /g) and total pore volume. Meanwhile, the contents of Fe 2+ and Mn 3+ decreased significantly, accompanied by a decrease in surface oxygen species, ultimately disrupting the redox cycles of active components. In addition, the synergistic poisoning by Na and K degraded oxygen-containing functional groups -OH and C=O, substantially reducing their abundance and inhibiting the synergistic reaction between Fe and Mn on the catalyst surface. This poisoning also reduced the mobility of O α species, resulting in a loss of active sites, which inhibited the SCR reaction. The coexistence of Na and K produced a synergistic poisoning effect that was stronger than individual poisoning effects, owing to enhanced occupation of active sites and disruption of electron transfer at the Fe-O-Mn interface. This study provides novel mechanistic insights into alkali-induced catalyst deactivation and offers guidance for the development of alkali-resistant SCR catalysts for industrial flue gas treatment.