XAFS Study on the Specific Deoxidation Behavior of Iron Titanate Catalyst for the Selective Catalytic Reduction of NOx with NH3. Issue 12 (2nd October 2013)

• Record Type: Journal Article
• Authors: Liu, Fudong; He, Hong; Xie, Lijuan
• Is Part Of: ChemCatChem. Volume 5:Issue 12(2013:Dec.)
• Page Start: 3760
• Page End: 3769
• Publication Date: 2013-10-02
• Subjects: Catalysis -- Periodicals; 541.39505
• DOI: 10.1002/cctc.201300565
• Languages: English
• ISSNs: 1867-3880

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The environmentally friendly catalyst iron titanate (FeTiO<sub><italic>x</italic></sub>) was reported to be very active for the selective catalytic reduction of NO<sub><italic>x</italic></sub> with NH<sub>3</sub> (NH<sub>3</sub>‐SCR), with high N<sub>2</sub> selectivity and H<sub>2</sub>O/SO<sub>2</sub> durability in the medium temperature range, and the specific microstructure of iron titanate crystallites as the active phase was determined. In consideration of the probable existence of a redox cycle between Fe<sup>3+</sup> and Fe<sup>2+</sup> species in the NH<sub>3</sub>‐SCR reaction, the deoxidation behavior of the FeTiO<sub><italic>x</italic></sub> catalyst in an H<sub>2</sub> temperature‐programmed reduction process was studied extensively by X‐ray absorption near‐edge structure (XANES) and extended X‐ray absorption fine‐structure (EXAFS) methods. Owing to the presence of an electronic inductive effect between Fe and Ti species in the unique edge‐shared Fe<sup>3+</sup>(O)<sub>2</sub>Ti<sup>4+</sup> structure, the reducibility of Fe<sup>3+</sup> species in the FeTiO<sub><italic>x</italic></sub> catalyst was greatly enhanced compared with that in pristine Fe<sub>2</sub>O<sub>3</sub>, leading to the higher oxidation ability of Fe species in FeTiO<sub><italic>x</italic></sub>. In the H<sub>2</sub> temperature‐programmed reduction process, the well‐dispersed Fe<sup>3+</sup> species in iron titanate crystallites could be totally converted into Fe<sup>2+</sup> in the form of ilmenite FeTiO<sub>3</sub> below 500 °C, whereas pristine Fe<sub>2</sub>O<sub>3</sub> could only be reduced to Fe<sub>3</sub>O<sub>4</sub> up to this temperature point. The typical NH<sub>3</sub>‐SCR reaction is usually conducted below 500 °C, and the enhanced oxidation ability of Fe<sup>3+</sup> species in FeTiO<sub><italic>x</italic></sub> catalyst is responsible for its excellent catalytic NO<sub><italic>x</italic></sub> reduction performance at low temperatures. Based on XANES linear fitting and EXAFS curve‐fitting results, the specific deoxidation process of the FeTiO<sub><italic>x</italic></sub> catalyst was proposed, which can provide useful information for the characterization of the microstructure and redox ability of active sites simultaneously in mixed oxide catalysts for certain catalytic reactions.</p> </abstract>