Effects of Cl ions on low-temperature NO conversion by NH3 over V2O5-WO3/TiO2 catalysts
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摘要: 考察添加不同含量Cl离子对浸渍法制备的Cl-V2O5-WO3/TiO2催化剂低温NO转化率的影响。随着Cl离子质量添加量从0增加到2.5%，Cl-V2O5-WO3/TiO2催化剂NO转化率先升高后降低，结合在含有SO2和H2O的SCR实验结果，确定1.5% Cl-V2O5-WO3/TiO2为性能最优催化剂。在反应温度为149-362℃，NO转化率大于95%；在145-385℃，NO转化率大于90%。采用XRF、BET、XRD、TG、FT-IR和H2-TPR等方法表征了催化剂的物理化学性能和结构。结果表明，在反应气氛中加入SO2和H2O后，催化剂比表面积和孔容均减小，副反应产物含有NH4+和SO42-。适量Cl离子可以抑制硫物种沉积，减少副反应产物生成，增强催化剂抗中毒能力。Abstract: The Cl-V2O5-WO3/TiO2 catalysts were prepared by impregnation methods. With the Cl ions content increased from 0 to 2.5%, the NO conversion of Cl-V2O5-WO3/TiO2 catalysts increased at first and then decreased. Combined with the experimental results, 1.5% Cl-V2O5-WO3/TiO2 catalyst was the optimal catalyst, NO conversion was higher than 95% in the range of 149-362℃, and NO conversion was higher than 90% in the temperature range of 145-385℃. The catalysts were characterized by XRF, BET, XRD, TG, FT-IR and H2-TPR. The specific surface area and pore volume of the catalysts decreased in different degrees after adding SO2 and H2O in reactant gas. The poisoned catalysts deposited sulfur species and contained NH4+ and SO42-. Adding appropriate amount of Cl ions inhibited the formation of side byproducts and enhanced the poisoning resistance of V2O5-WO3/TiO2 catalyst.
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Key words:
- Cl ions /
- low temperature SCR /
- sulfur resistance /
- catalyst poisoning
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图 2 SO2对Cl-3VWT催化剂NO转化率的影响
Figure 2 Effect of SO2 on NO conversion of the Cl-3VWT catalysts
reaction conditions: φNH3= φNO=0.07%, φSO2=0.03%, φO2=5%, N2 balance, GHSV=30000 h-1
图 3 SO2和H2O对Cl-3VWT催化剂NO转化率的影响
Figure 3 Effect of SO2 and H2O on NO
conversion of the Cl-3VWT catalysts reaction conditions: φNH3= φNO=0.07%, φO2=5%, φSO2=0.035%, φH2O=15%, N2 balance, GHSV=30000 h-1
图 4 Cl-3VWT催化剂的XRD谱图
Figure 4 X-ray diffraction patterns of the Cl-3VWT catalysts
a: 0Cl-3VWT; b: 0.5Cl-3VWT; c: 1Cl-3VWT; d: 1.5Cl-3VWT; e: 2.5Cl-3VWT; f: 0Cl-3VWTSH; g: 1.5Cl-3VWTSH
图 5 Cl-3VWT催化剂在含有SO2和H2O的SCR反应前后的FT-IR谱图
Figure 5 FT-IR spectra of the Cl-3VWT catalysts before and after adding SO2 and H2O
图 6 Cl-3VWT催化剂在含有SO2和H2O的SCR反应前后的TG曲线
Figure 6 TG curves of the Cl-3VWT catalysts before and after adding SO2 and H2O
图 7 Cl-3VWT催化剂在含有SO2和H2O的SCR反应前后的H2-TPR谱图
Figure 7 H2-TPR profiles of the Cl-3VWT catalysts before and after adding SO2 and H2O
表 1 反应气氛中通入SO2后Cl-3VWT催化剂的NO转化率趋势线
Table 1 Trend lines describing the effect of SO2 on NO conversion over the Cl-3VWT catalysts
Sample Equation of trend line Correlation coefficient R2 0Cl-3VWT Y=99.28-0.39X 0.98 1.25Cl-3VWT Y=99.58-0.19X 0.99 1.5Cl-3VWT Y=99.33-0.02X 0.99 2.5Cl-3VWT Y=98.56-0.27X 0.98 
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表 2 Cl-3VWT催化剂的比表面积
Table 2 Specific surface area of the Cl-3VWT catalysts
No. Sample Specific surface area A/(m2·g-1) 1 0Cl-3VWT 82 2 0.5Cl-3VWT 82 3 1Cl-3VWT 83 4 1.25Cl-3VWT 83 5 1.5Cl-3VWT 84 6 2.5Cl-3VWT 84
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表 3 催化剂的物理性质对比
Table 3 Comparison of physical properties of the Cl-3VWT catalysts
Characterization 0Cl-3VWT 0Cl-3VWTSH 1.5Cl-3VWT 1.5Cl-3VWTSH Specific surface area A/(m2·g-1) 82 70 84 73 Pore volume v/(cm3·g-1) 0.32 0.28 0.33 0.29 Average pore diameter d/nm 15.6 15.6 16.1 16.1 Component weight fraction/% XRF TiO2 90.0 90.8 88.6 88.9 V2O5 3.01 2.07 2.95 2.50 WO3 5.92 4.36 5.94 5.26 Cl 0.00 0.00 1.46 1.43 SO3 0.13 1.70 0.10 0.70 Temperature range t/℃ weight loss fraction/% TG 25-600 2.83 5.45 3.03 5.94 25-100 1.28 1.48 1.22 2.42 220-440 0.62 2.68 0.63 2.40
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