Revealing the promotional effect of Ce doping on the low-temperature activity and SO2 tolerance of Ce/FeVO4 catalysts in NH3-SCR
Elimination of NO x from the non-electric industrial boilers has become priority under the effective implementation of ultra-low emissions. A series of Ce-promoted FeVO 4 catalysts with improved acidity and reducibility have been synthesized in this work. Thereinto, 10Ce/FeVO 4 exhibited an optimum low-temperature performance with 90% of NO x conversion and 95% of N 2 selectivity at 200–300 °C which was kept nearly unchanged with different concentrations of SO 2 ranging from 50 ppm to 200 ppm, showing a superior sulfur tolerance. An array of well-designed experiments has demonstrated that Ce mainly existed as CeVO 4 under a low doping content (1 wt%) on FeVO 4 , which could efficiently increase the amount of acid sites. With more cerium (5–12 wt%) loading on FeVO 4 , the appearance of CeO 2 further resulted in a strong interaction between cerium species and ion species, thus significantly improving the low-temperature catalytic activity . Therefore, the optimum coexistence of CeVO 4 and CeO 2 over 10Ce/FeVO 4 modulated its Brønsted acid and enhanced its redox circulation of Fe 3+ species. Moreover, the NH 3 -SCR reaction pathways of 10Ce/FeVO 4 were broadened from only Eley-Rideal to both Eley-Rideal and Langmiur-Hinshelwood mechanisms after Ce loading on FeVO 4 catalyst. With the presence of SO 2 , the S O/S-O deriving from the generated Ce 2 (SO 4 ) 3 and NH 4 HSO 4 increased the Brønsted acid sites, inducing a satisfying SO 2 tolerance of 10Ce/FeVO 4 catalyst, although the Langmiur-Hinshelwood pathway of 10Ce/FeVO 4 was immediately cut off due to the competitive adsorption of gaseous SO 2 and NO x . This work exemplifies a promising strategy for developing an ideal low-temperature NH 3 -SCR catalyst with good SO 2 resistance.
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