Effect of the calcination temperature of cerium–zirconium mixed oxides on the structure and catalytic performance of WO 3 /CeZrO 2 monolithic catalyst for selective catalytic reduction of NO x with NH 3

• Published in: RSC advances Vol. 7; no. 39; pp. 24177 - 24187
• Main Authors: Xu, Haidi, Sun, Mengmeng, Liu, Shuang, Li, Yuanshan, Wang, Jianli, Chen, Yaoqiang
• Format: Journal Article
• Language: English
• Published: 2017
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C7RA03054A

A series of WO
3
/CeZrO
2
catalysts, prepared at different calcination temperatures (400, 500, 600 and 700 °C) of cerium–zirconium mixed oxides (CeZrO
2
) for the selective catalytic reduction of NO
x
with ammonia (NH
3
-SCR), were investigated
via
various characterizations, such as N
2
physisorption, XRD, Raman, NH
3
-TPD, DRIFTS, XPS and H
2
-TPR. The catalytic performance of NH
3
-SCR was remarkably promoted by modestly increasing the calcination temperature of CeZrO
2
: WO
3
/CeZrO
2
-500 possessed the lowest light-off temperature (173 °C) and complete conversion temperature (205 °C), while W/CeZrO
2
-600 could achieve greater than 90% NO
x
conversion in a broad temperature range of 220–455 °C. The characterization results indicated that modest enhancement of the calcination temperature of CeZrO
2
was beneficial to stabilizing the structure of the catalysts. The largest amount of Lewis acid sites, Ce
3+
and surface active oxygen species, as well as strong redox properties of WO
3
/CeZrO
2
-500 should together contribute to its better low-temperature deNO
x
activity. Moreover, increasing the calcination temperature of cerium–zirconium mixed oxides resulted in the enhancement of Brønsted acid sites, which was responsible for the widened operation temperature window. Therefore, WO
3
/CeZrO
2
serial catalysts with appropriate calcination treatment of CeZrO
2
would be a good choice for the removal of NO
x
emitted from diesel engines.