FT-IR study of the nature and reactivity of surface NOx compounds formed after NO adsorption and NO + O2 coadsorption on zirconia- and sulfated zirconia-supported cobalt

Promotional effect of Nb additive on the activity and hydrothermal stability for the selective catalytic reduction of NO with NH3 over CeZrO catalyst

“…5(B) shows the in situ DRIFTS results of NO x adsorption over Nb 2 O 5 and CeNb a Zr 2 O x catalysts. After NO + O 2 adsorption for 1.0 h and N 2 purge for another 0.5 h, a couple of distinct bands assigned to bidentate nitrate (1583 and 1560 cm −1 ) and bridging nitrate (1609, 1622, 1237 and 1217 cm −1 ) were observed [34,[38][39][40]. It was quite clear that the introduction of Nb decreased both the intensity and quantity of bands assigned to nitrate species, which might arise from the fact that the addition of Nb promoted the formation of more acid sites together with fewer alkali sites where the nitrate species adsorbed [33].…”

Manganese–niobium mixed oxide catalyst for the selective catalytic reduction of NOx with NH3 at low temperatures

“…11B. After NO + O 2 adsorption and N 2 purge, the sample surfaces were mainly covered by three types of nitrate, including monodentate nitrate (ˆ3 high at 1544 cm À1 ), bidentate nitrate (ˆ3 high at 1575 cm À1 andˆ3 low at 1280 cm À1 ), and bridging nitrate (ˆ3 high at 1622 cm À1 andˆ3 low at 1228 cm À1 ) [28,36,37]. On the MnO x catalyst, the intensity of NO x adsorption peaks were stronger than that on Mn 2 Nb 1 O x and NbO x catalysts, which is in accordance with the NO x -TPD results.…”

Fourier Transforms Infrared Spectroscopy Applied in Selective Catalytic Reduction of NO by Acetylene

“…As shown in Fig. 9, Two bands at 1598 and 1629 cm -1 due to bidenate and bridging nitrates (Li et al, 2007;Tsyntsarski et al, 2003;Li et al, 2005a) respectively appeared on HZSM-5 and HFER when the zeolites were exposed to NO+O 2 at 250 o C. By comparing the band increasing in intensity at 1629 and 1598 cm -1 over the zeolites, it can be known that the nitrate species formation was faster over HFER than that over HZSM-5. Obviously, the relative nitrate species formation rate coincides well with the relative C 2 H 2 -SCR activity for the two parent zeolites.…”

“…However, some authors have claimed that activation of NO x occurs first, forming nitrous surface species, such as nitro (Meunier et al, 2000), nitroso (Poignant et al, 2001, Gerlach et al, 1999, nitrosonium ions (Gerlach et al, 1999, Ingelsten et al, 2005, nitrate or nitrite (Luo et al,2007, Anunziata et al, 2007 over the catalyst. For instance, bridging and bidentate nitrates were reported to be produced first by co-adsorption of NO+O 2 on Co/SO 4 2− -ZrO 2 (Tsyntsarski et al, 2003), BaY (Sedlmair et al, 2003a) and Ag/Al 2 O 3 (Bentrup et al, 2005). Tsyntsarski et al (Tsyntsarski et al, 2003) have suggested that both bridging and bidentate nitrates are active species of the HC-SCR.…”

“…For instance, bridging and bidentate nitrates were reported to be produced first by co-adsorption of NO+O 2 on Co/SO 4 2− -ZrO 2 (Tsyntsarski et al, 2003), BaY (Sedlmair et al, 2003a) and Ag/Al 2 O 3 (Bentrup et al, 2005). Tsyntsarski et al (Tsyntsarski et al, 2003) have suggested that both bridging and bidentate nitrates are active species of the HC-SCR. Mihaylov et al (Mihaylov et al, 2004) have reported that monodentate nitrates on Ni-HZSM-5 are highly reactive towards methane.…”