Study on the synergistic effect of CeO2 and WO3 on the catalytic performance of CeO2-WO3 for the selective catalytic reduction of NOx by NH3
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摘要: 采用原位自组装法分别制备纯CeO2、WO3和CeO2-WO3（CW）催化剂，并研究其NH3选择性催化还原NOx的催化活性。结果表明，WO3的加入使得CW催化剂以微孔为主且具有最大的孔容和较大的比表面积，提高了其催化性能。WO3的加入增强了Ce和W之间的相互作用，显著地提升了Ce3+和Oα的含量。CW催化剂具有最多的酸性位点。因此，CW催化剂催化活性最好，在250-400 ℃温度下NOx转化率为100%。Abstract: The CeO2, WO3 and CeO2-WO3 (donated as CW) catalysts were prepared by in-situ self-assembly method and used for the low-temperature selective catalytic reduction (SCR) of NOx with NH3. The results showed that CW catalysts possessed the most microspore and maximum pore volume and larger specific surface area with the addition of WO3, resulting in the improvement to the catalytic performance. Besides, the interaction of Ce and W was improved by the introduction of WO3, which could increase the amount of Ce3+ and Oα. Meanwhile, the enhancement of weak and medium strong acid sites was caused by the introduction of WO3. Thus, CW catalyst showed the best SCR activity and its NOx conversion at the value of 100% maintained in a wide temperature window ranging from 250 to 400 ℃.
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Key words:
- WO3 /
- CeO2 /
- selective catalytic reduction /
- surface acidity /
- redox property
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图 1 (a) WO3、CeO2和CW催化剂随温度变化的转化率；(b)WO3、CeO2和CW催化剂随温度变化的N2选择性
Figure 1 NOx conversion (a) and N2 selectivity (b) for the WO3, CeO2 and CW catalysts
图 3 (a) WO3、CeO2和CW催化剂的N2吸附-脱附等温线和(b)孔径分布
Figure 3 N2 adsorption-desorption results of the WO3, CeO2 and CW catalysts (a): the N2 adsorption-desorption isotherms; (b): the BJH pore size distributions
图 4 WO3、CeO2和CW催化剂的NH3-TPD谱图
Figure 4 NH3-TPD profiles of the WO3, CeO2 and CW catalysts
图 5 WO3、CeO2和CW催化剂的H2-TPR谱图
Figure 5 H2-TPR profiles of the WO3, CeO2 and CW catalysts
图 6 催化剂的XPS谱图
Figure 6 XPS spectra of the WO3, CeO2 and CW catalysts
(a): W 4f; (b): Ce 3d; (c): O 1s
表 1 WO3、CeO2和CW催化剂的表面原子浓度
Table 1 Surface atomic concentration of the WO3, CeO2 and CW catalysts
Sample Surface atomic concentration watomic/% Ce W O Ce3+/(Ce4++Ce3+) Oα/(Oα+Oβ) CeO2 14.83 - 52.99 28.37 38.01 WO3 - 20.47 55.47 - 35.32 CW 11.99 5.19 49.98 30.26 64.50 calculated from the XPS results (atomic %) 
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