In situ-DRIFTS Study of Sb–V–CeO2/TiO2 Catalyst Under Standard and Fast NH3-SCR Conditions

Boosting SO2-Resistant NOx Reduction by Modulating Electronic Interaction of Short-Range Fe–O Coordination over Fe2O3/TiO2 Catalysts

“…Titrating pre-adsorbed NO + SO 2 + O 2 with NH 3 over Fe 2 O 3 /TiO 2 reveals that the presence of SO 2 precludes formation of gaseous NO 2 but induces formation of surface nitro species (1364 cm –1 ) . Large quantities of sulfate (1346 and 1313 cm –1 ) and surface sulfites (908 and 1098 cm –1 ) species are also detected during NO + SO 2 + O 2 adsorption. , After the introduction of NH 3 , amide (1290 cm –1 ) and NH 4 + (1417 cm –1 ) species emerge over the catalyst. , By pre-dosing NO + SO 2 + O 2 on Fe 2 O 3 /S–TiO 2 , bidentate nitrate species (1385 cm –1 ) is found to be the dominant adsorbate, together with trace amounts of sulfate/sulfite species . With the introduction of NH 3 , the bidentate nitrate is quickly consumed, and then, a strong band of NH 4 + species emerges accompanied with that of amide species due to the enhanced acidity of Fe 2 O 3 /S–TiO 2 .…”

“…To gain further details on the speciation of adsorbed NH 3 , in situ DRIFT measurements were carried out after NH 3 adsorption for 1 h at 280 °C. The results in Figure 4C show that large quantities of NH 4 + (1423 cm −1 ) and amide (−NH 2 , 1271 cm −1 ) species generate on Fe 2 O 3 /S−TiO 2 , 43,44 but only a weak signal of molecular NH 3 (1178 cm −1 ) is detected on Fe 2 O 3 /TiO 2 . 45 In situ DRIFT spectra for NO + O 2 oxidation for 1 h at 280 °C in Figure 4D reveal generation of a strong bidentate nitrate peak (1370 cm −1 ) on Fe 2 O 3 /S−TiO 2 , whereas only one extremely weak NO 2 peak (1604 cm −1 ) is found on Fe 2 O 3 /TiO 2 , which has been suggested in the past as a result of NO oxidation by large Fe 2 O 3 particles.…”

“…47,49 After the introduction of NH 3 , amide (1290 cm −1 ) and NH 4 + (1417 cm −1 ) species emerge over the catalyst. 43,44 By pre-dosing NO + SO 2 + O 2 on Fe 2 O 3 /S−TiO 2 , bidentate nitrate species (1385 cm −1 ) is found to be the dominant adsorbate, together with trace amounts of sulfate/sulfite species. 46 With the introduction of NH 3 , the bidentate nitrate is quickly consumed, and then, a strong band of NH 4 + species emerges accompanied with that of amide species due to the enhanced acidity of Fe 2 O 3 /S− TiO 2 .…”