TY - JOUR
T1 - Pd-promoted WO3-ZrO2 for low temperature NOx storage
AU - Ji, Yaying
AU - Bai, Shuli
AU - Xu, Dongyan
AU - Qian, Dali
AU - Wu, Zili
AU - Song, Yang
AU - Pace, Robert
AU - Crocker, Mark
AU - Wilson, Karen
AU - Lee, Adam
AU - Harris, Deb
AU - Scapens, Dave
N1 - Publisher Copyright:
© 2019 Elsevier B.V.
PY - 2020/5/5
Y1 - 2020/5/5
N2 - Pd-promoted ZrO2 and WO3-ZrO2 (W-Zr) were investigated for low temperature NOx adsorption and release. Pd-promoted W-Zr exhibited high NOx storage efficiency at short storage times, subsequently releasing ∼95% of the stored NOx upon thermal ramping to 350 °C. DRIFTS studies demonstrated that Pd increased nitrate formation relative to nitrite during NOx storage on both Pd-Zr and Pd-W-Zr. Moreover, Pd sites on Pd-W-Zr played a major role in NOx storage, the ad-species being readily removed by 350 °C. From NO- and CO-DRIFTS data, it is inferred that Pd on the acidic W-Zr support was present as mainly cationic species, and was therefore able to adsorb NO, whereas on ZrO2 Pd was not able to directly store NOx. Co-feeding CO with NO resulted in increased NOx storage capacity for Pd-W-Zr, which on the basis of DRIFTS measurements is attributed to the formation of Pd2+(CO)(NO) complexes.
AB - Pd-promoted ZrO2 and WO3-ZrO2 (W-Zr) were investigated for low temperature NOx adsorption and release. Pd-promoted W-Zr exhibited high NOx storage efficiency at short storage times, subsequently releasing ∼95% of the stored NOx upon thermal ramping to 350 °C. DRIFTS studies demonstrated that Pd increased nitrate formation relative to nitrite during NOx storage on both Pd-Zr and Pd-W-Zr. Moreover, Pd sites on Pd-W-Zr played a major role in NOx storage, the ad-species being readily removed by 350 °C. From NO- and CO-DRIFTS data, it is inferred that Pd on the acidic W-Zr support was present as mainly cationic species, and was therefore able to adsorb NO, whereas on ZrO2 Pd was not able to directly store NOx. Co-feeding CO with NO resulted in increased NOx storage capacity for Pd-W-Zr, which on the basis of DRIFTS measurements is attributed to the formation of Pd2+(CO)(NO) complexes.
KW - Cations
KW - DRIFTS
KW - Nitrosyl complex
KW - Palladium
KW - Passive NOx adsorber
KW - Tungstated zirconia
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U2 - 10.1016/j.apcatb.2019.118499
DO - 10.1016/j.apcatb.2019.118499
M3 - Article
AN - SCOPUS:85076276877
SN - 0926-3373
VL - 264
JO - Applied Catalysis B: Environmental
JF - Applied Catalysis B: Environmental
M1 - 118499
ER -