in-situ DRIFTs study on different exposed facets of VOx-MnOx/CeO2 catalysts for low-temperature NH3-SCR
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摘要: 为实现低温（200-250℃）NH3-SCR烟气脱硝，开发出了一种高分散暴露CeO2不同晶面的VOx-MnOx/CeO2低温脱硝催化剂。脱硝性能评价实验结果表明，暴露{110}晶面的VOx-MnOx/CeO2-R催化剂在很宽的温度范围内（220-330℃）都保持了>95%的脱硝效率。原位漫反射红外分析结果可知，暴露{110}晶面的VOx-MnOx/CeO2-R催化剂表面更易发生NH3和NO吸附，进而提高NO的转化效率。气态NH3在VOx-MnOx/CeO2-R催化剂上吸附生成NH3（L）和NH4+（B），该中间体与NO吸附的中间体桥联硝酸盐和双齿硝酸盐反应生成N2和H2O，并遵循Langmuir-Hinshelwood机理。
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关键词:
- VOx-MnOx/CeO2 /
- 暴露晶面 /
- 低温脱硝 /
- 原位红外
Abstract: In order to achieve the low-temperature (200-250℃) NH3-SCR, highly dispersed VOx-MnOx/CeO2 catalysts with different exposed facets were produced. The NH3-SCR performance results indicate that the NO conversion over VOx-MnOx/CeO2-R with preferentially exposed {110} facets can achieve NO conversion >95% over a wide temperature span of 220-330℃. From the in-situ DRIFTs, gaseous NH3 and NO are favorable to be absorbed on the surface of the VOx-MnOx/CeO2-R catalyst with preferentially exposed {110} facets, which improves the efficiency of NO conversion. The mechanism study via in situ DRIFTs demonstrates that the well dispersed vanadium species on CeO2 {110} absorb NH3 to generate NH3(L) and NH4+(B) species, which in turn become highly reactive toward bridging nitrate and bidentate nitrate species to form N2 and H2O according to the Langmuir-Hinshelwood mechanism.-
Key words:
- VOx-MnOx/CeO2 /
- exposed facets /
- low-temperature NH3-SCR /
- in-situ DRIFTs
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图 1 随温度变化的NH3-SCR脱硝性能评价
Figure 1 NO conversion (a) and N2 selectivity (b) as a function of temperature in NH3-SCR
图 2 TEM、HRTEM照片和形貌示意图
Figure 2 TEM images, HRTEM images, and schematic illustrations of ((a1)-(a3)) CeO2-R, ((b1)-(b3)) CeO2-P, and ((c1)-(c3)) CeO2-C samples
图 3 CeO2-R和不同形貌的VOx-MnOx/CeO2催化剂的XRD谱图
Figure 3 XRD patterns of CeO2-R and various corresponding VOx-MnOx/CeO2 samples
图 4 暴露不同晶面VOx-MnOx/CeO2-R/P/C催化剂的H2-TPR谱图(a)和吸附NH3活性物种分析(b)
Figure 4 H2-TPR profiles (a) and adsorbed-NH3 species (b) of the VOx-MnOx/CeO2-R/P/C catalysts
图 5 220℃下NH3吸附在催化剂上的in-situ DRIFTs谱图
Figure 5 in-situ DRIFTs spectra of NH3 adsorption exposed to a flow of 0.05% NH3 at 220℃
(a) VOx-MnOx/CeO2-R, (c) VOx-MnOx/CeO2-P, (e) VOx-MnOx/CeO2-C; and the corresponding mapping results: (b) VOx-MnOx/CeO2-R, (d) VOx-MnOx/CeO2-P, (f) VOx-MnOx/CeO2-C
图 6 220℃下NO+O2吸附在催化剂上的in-situ DRIFTs谱图
Figure 6 in-situ DRIFTs spectra of NO+O2 adsorption exposed to a flow of 0.05% NO at 220℃
(a) VOx-MnOx/CeO2-R, (c) VOx-MnOx/CeO2-P, (e) VOx-MnOx/CeO2-C; and the corresponding mapping results: (b) VOx-MnOx/CeO2-R, (d) VOx-MnOx/CeO2-P, (f) VOx-MnOx/CeO2-C
图 7 220℃下NO+O2与催化剂上的预吸附NH3反应的in-situ DRIFTs谱图
Figure 7 in-situ DRIFTs spectra of NO+O2 reacted with pre-adsorbed NH3 at 220℃
(a) VOx-MnOx/CeO2-R, (c) VOx-MnOx/CeO2-P, (e) VOx-MnOx/CeO2-C; and the corresponding mapping results: (b) VOx-MnOx/CeO2-R, (d) VOx-MnOx/CeO2-P, (f) VOx-MnOx/CeO2-C
表 1 不同样品的BET和N2吸脱附性质数据
Table 1 Quantitative data from the analysis of different samples
Sample Exposed
planeBET surface
area A/
(m2·g-1)Total pore
volume v/
(cm3·g-1)VOx-MnOx/CeO2-R {110}, {100} 106.6 0.32 VOx-MnOx/CeO2-P {111}, {100} 92.5 0.13 VOx-MnOx/CeO2-C {100} 73.1 0.21 
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