Enhancing SO2-shielding effect and Lewis acid sites for high efficiency in low-temperature SCR of NO with NH3: Reinforced electron-deficient extent of Fe3+enabled by Ti4+in Fe2O3

An ideal catalyst that can be used for the selective catalytic reduction (SCR) of NO at low temperature should have a high activity and ability to resist SO2. Herein, Ti-doped Fe2O3 (Ti-Fe2O3) nanoparticles that extraordinarily convert NO (T90, 200 degrees C) and highly resist SO2 meet this requirement. In the presence of 100 ppm SO2, the optimal Ti-Fe2O3 can convert 90% NO at 220 degrees C for 24 h. With the addition of Ti4+, the electrons around Fe3+ migrate toward Ti4+, strengthening the electron-deficient tendency of Fe3+. Therefore, electron-donating NH3 is preferentially adsorbed by Fe3+, endowing Ti-Fe2O3 with the ability to resist SO2 and exceptionally tolerate SO2 at low temperature. Besides, based on the strength of the embedded Ti4+, a large number of Bronsted acid sites are converted to Lewis acid sites to speed the reaction rate of SCR below 210 degrees C. High anti-SO2 capacity and adequate Lewis acid sites maximize the efficiency of Ti-Fe2O3 in reducing NO.

Automated summary

Ti-doped Fe2O3 nanoparticles show high activity and resistance to SO2, allowing for efficient reduction of NO at low temperatures. The addition of Ti4+ strengthens the electron-deficient tendency of Fe3+, enabling the catalyst to selectively adsorb NH3 and resist SO2. In addition, the embedded Ti4+ also increases the number of Lewis acid sites, enhancing the reaction rate of SCR.