Promotional effects of Fe2O3 additive on the NH3-SCR activity and alkali resistance of MoTiOx catalysts

Abstract

Catalyst is the core of selective catalytic reduction (SCR) technology, and an ideal SCR technology requires that the catalyst should have high activity and resistance to alkali metal poisoning. Therefore, in this paper, the influence of Na poisoning on the catalytic performance of Fe2O3-MoTiOx catalysts in the selective catalytic reduction (SCR) reaction was investigated, and the anti-alkali mechanism was revealed. The Fe2O3-MoTiOx catalyst demonstrated the NO conversion was 90 % at a broad temperature range of 225-400 °C when the Fe2O3 loading ratio was 20 wt%. Besides, 80 % NO conversion rate of the Fe2O3-MoTiOx catalyst at 320 °C was still achieved even at a Na+ concentration of 300 μmol g-1. The phenomenon was attributed to the interaction between Fe and Ti species, which could generate more Lewis acid centers and facilitate the adsorption activation of NH3. During the Na poisoning process, Na ions predominantly adsorbed on the Fe2O3, effectively safeguarding the MoTiOx catalyst. Additionally, although the Brønsted acid sites were deteriorated because of Na poisoning, the abundant Lewis acid sites were preserved for NHx adsorption. Therefore, the Na-poisoned Fe2O3-MoTiOx catalyst maintained efficient NH3 adsorption and NO activation. The work provided theoretical guidance and data support for the development of novel alkali-resistant SCR catalysts.