Enhanced catalytic activity of Fe–Ce catalysts determined by synergistic effect of different precursors in selective catalytic reduction of NOx with NH₃

Abstract

Background: Developing environmentally benign and non-vanadium SCR catalysts remains a challenging task for NOx abatement. In this article, Fe-Ce catalysts including Fe-Ce(S) and Fe(S)-Ce catalysts with different molar ratios of Fe/Ce were synthesized by different precursors of active species expecting to gain high catalytic activity for the selective catalytic reduction (SCR) of NOx with NH 3 in a wide temperature range.Results: The Fe-Ce(S) catalyst exhibited better catalytic activity than the Fe(S)-Ce catalyst. The characterization results indicated the Fe-Ce(S)catalyst possessed better dispersion of active species, which would favor the contact of active sites and reactant molecules and thus enhance the catalytic performance. Moreover, higher ratios of Fe 3+ and Ce 3+ and more surface chemisorbed oxygen were observed over the Fe-Ce(S) catalyst. In addition, the Fe-Ce(S) catalyst held better low-temperature redox properties and more weak acid sites.Conclusions: The precursor effect was closely related to the catalytic activity of catalysts. All of the mentioned above might be the main reasons for the superior catalytic performance of the Fe-Ce(S) catalyst, especially at low temperatures. These findings indicate that Fe-Ce(S) catalyst is a promising catalyst for the SCR reaction to replace V-W-Ti catalysts and can provide guidance for the development of environmentally benign and non-vanadium SCR catalysts.

In situ construction of halogen MOF bifunctional catalysts for synergistic removal of NO and Hg0

“…40 Ce 3+ leads to charge imbalance, oxygen vacancies, and unsaturated chemical bonds on the catalyst's surface, which are essential in the NH 3 -SCR reaction. 41,42 u ′ and v ′, u ′′ and v ′′ are attributed to Ce 4+ , indicating the coexistence of Ce in the oxidation states of +3 and +4. Cu and Ce ions can shift the redox equilibrium towards Ce 3+ + Cu 2+ ↔ Ce 4+ + Cu + , facilitating synergistic catalytic activity interactions and promoting more surface oxygen vacancies, thereby accelerating the redox cycle, which in turn facilitates the reaction.…”

“…u 0 and v 0 correspond to Ce 3+ atoms 40. Ce 3+ leads to charge imbalance, oxygen vacancies, and unsaturated chemical bonds on the catalyst's surface, which are essential in the NH 3 -SCR reaction 41,42. u′ and v′, u″ and v″ are attributed to Ce 4+ , indicating the coexistence of Ce in the oxidation states of +3 and +4.…”

Promoting effect ofN2calcination onFeCeOxfor selective catalytic reduction ofNOxwithNH3

“…Thus, more Fe 3+ formed on the surface of Fe 9 CeO x -N 2 , which was beneficial for the NH 3 -SCR reaction. 46 The difference in the Ce species state between the two fresh catalysts was also investigated. The spectra of Ce 3d could be divided into species assigned to Ce 3+ (u, u 1 , u 2 , u 3 ) and Ce 4+ (v, v 1 , v 2 , v 3 ) (Fig.…”

“…The values were 58.8% and 63.2% for Fe 9 CeO x ‐air and Fe 9 CeO x ‐N 2 , respectively. Thus, more Fe 3+ formed on the surface of Fe 9 CeO x ‐N 2 , which was beneficial for the NH 3 ‐SCR reaction 46 …”