Insight into the Alkali Resistance Mechanism of FeMoTiO x Catalysts for NH 3 Selective Catalytic Reduction of NO: Self-Defense Effects of MoO x for Alkali Capture.

The deactivation of selective catalytic reduction (SCR) catalysts caused by alkali metal poisoning remains an insurmountable challenge. In this study, we examined the impact of Na poisoning on the performance of Fe and Mo co-doped TiO 2 (Fe a Mo b TiO x ) catalysts in the SCR reaction and revealed the related alkali resistance mechanism. On the obtained Fe 1 Mo 2.6 TiO x catalyst, the synergistic catalytic effect of uniformly dispersed FeO x and MoO x species leads to remarkable catalytic activity, with over 90% NO conversion achieved in a wide temperature range of 210-410 °C. During the Na poisoning process, Na ions predominantly adsorb on the MoO x species, which exhibit stronger alkali resistance, effectively safeguarding the FeO x species. This preferential adsorption minimizes the negative effect of Na poisoning on Fe 1 Mo 2.6 TiO x . Moreover, Na poisoning has little influence on the Eley-Rideal reaction pathway involving adsorbed NH x reacting with gaseous NO x . After Na poisoning, the Lewis acid sites were deteriorated, while the abundant Brønsted acid sites ensured sufficient NH x adsorption. As a benefit from the self-defense effects of active MoO x species for alkali capture, Fe a Mo b TiO x exhibits exceptional alkali resistance in the SCR reaction. This research provides valuable insights for the design of highly efficient and alkali-resistant SCR catalysts.