Preparation of honeycombed holmium-modified Fe-Mn/TiO2 catalyst and its performance in the low temperature selective catalytic reduction of NOx
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摘要: 采用模压法制备了蜂窝状Ho改性的Fe-Mn/TiO2催化剂，研究了结构助剂、黏合剂和造孔剂等对成型催化剂低温选择催化还原（SCR）脱硝性能的影响。优选出一套理想的成型参数：水粉质量比为40%且逐次分批加入；结构助剂玻璃纤维的用量为10%（质量分数）；黏合剂羧甲基纤维素的用量为5%（质量分数）；助挤剂甘油的添加量为10%（质量分数）且分批加入；造孔剂活性炭粉的用量为2%（质量分数）。该蜂窝状催化剂在120 ℃下脱硝率维持在90%以上，并且在SO2体积分数低于0.02%时具有一定的抗硫抗水性。表征结果表明，成型后蜂窝状催化剂比表面积降低，颗粒分散程度明显减弱，并且表面酸量和表面Mn4+含量下降，对催化活性有一定的影响。Abstract: A series of honeycombed holmium-modified Fe-Mn/TiO2 catalysts were prepared by moulding method and their performance in the low temperature selective catalytic reduction (SCR) of NOx was investigated. The forming process was optimized as:the mass content of water in the forming additives is 40%, in which 10% structure strengthening agent (glass fiber), 5% binder (carboxymethyl cellulose), 10% squeezing agent (glycerin), 5% pore-forming agent (activated carbon) and a little lubricants (liquid paraffin) are added. The honeycombed Fe-Ho-Mn/TiO2 catalyst prepared under these conditions exhibits excellent performance in the low-temperature SCR of NOx; the conversion of NOx exceeds 90% at 120℃ and a good resistance to SO2 and H2O is observed when the content of SO2 in the stream is lower than 0.02%. The characterization results indicated that in comparison with the parent powder holmium-modified Fe-Ho-Mn/TiO2 catalyst, the honeycombed catalyst exhibits lower surface area, more particle aggregation, and less acid sites and Mn4+ species on the surface, which has a certain negative influence on the catalytic performance of Fe-Ho-Mn/TiO2.
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Key words:
- holmium /
- selective catalytic reduction /
- de-NOx /
- low temperature /
- honeycombed /
- forming
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图 1 不同玻璃纤维含量下成型催化剂的机械强度
Figure 1 Mechanical strength of honeycombed catalysts with different glass fiber content
图 2 不同玻璃纤维含量下成型催化剂的脱硝效率
Figure 2 Activity of the honeycombed catalysts with different glass fiber contents in the SCR of NO the reaction stream contains 0.08% NH3, 0.08% NO, 5% O2 and balanced N2, with a GHSV of 4000 h-1
图 3 不同活性炭含量下成型催化剂的脱硝效率
Figure 3 Activity of the honeycombed catalysts with different activated carbon contents in the SCR of NO the reaction stream contains 0.08% NH3, 0.08% NO, 5% O2 and balanced N2, with a GHSV of 4000 h-1
图 4 不同浓度SO2对蜂窝状Fe-Ho-Mn/TiO2催化剂脱硝性能的影响
Figure 4 Activity of the honeycombed Fe-Ho-Mn/TiO2 catalyst in the SCR of NO with different SO2 contents the reactions are carried out 120 ℃ and the reaction stream contains 0.08% NH3, 0.08% NO, 5% O2 and balanced N2, with a GHSV of 4000 h-1
图 5 Fe-Ho-Mn/TiO2催化剂颗粒成型前后的SEM照片
Figure 5 SEM images of the parent powder Fe-Ho-Mn/TiO2 catalyst (a) and the honeycombed Fe-Ho-Mn/TiO2 catalysts ((b) and (c))
图 6 Fe-Ho-Mn/TiO2催化剂颗粒成型前后的NH3-TPD谱图
Figure 6 NH3-TPD profiles of the powder (a) and honeycombed (b) Fe-Ho-Mn/TiO2 catalysts
图 7 Fe-Ho-Mn/TiO2催化剂颗粒成型前后的XPS谱图
Figure 7 XPS spectra of powder and honeycombed Fe-Ho-Mn/TiO2 catalysts a: powder Fe-Ho-Mn/TiO2; b: honeycombed Fe-Ho-Mn/TiO2
表 1 不同黏合剂含量下成型催化剂的成型效果和机械强度
Table 1 Morphology and mechanical strength of the honeycombed catalysts with different binder contents
Entry Binder Content w/% Morphology Axial mechanical strength p/MPa 1 CMC 2.5 the mud viscosity is low and cracks occur after roasting 1.10 2 CMC 5 the mud viscosity is proper and it is easy to form 1.35 3 CMC 10 the mud viscosity is high and it is difficult to demold 0.94 4 PAM 5 the mud viscosity is low and it is difficult to bond and easy to crack after moulding 0.59 5 PAM 10 the mud viscosity is low and cracks occur after roasting 0.95 6 PAM 15 the viscosity is proper and it is easy to form 1.27 7 PAM 20 the mud viscosity is high and it is difficult to demold 0.98 
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表 2 不同活性炭粉含量下成型催化剂的机械强度和BET比表面积
Table 2 Mechanical strength and BET surface area of the honeycombed catalysts with different activated carbon contents
Entry AC content w/% Axial direction strength p/MPa ABET/ (m2·g-1) 1 0 1.35 72 2 1 1.34 79 3 2 1.34 83 4 3 1.31 84 5 4 1.25 85
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表 3 Fe-Ho-Mn/TiO2催化剂颗粒成型前后的BET比表面积、孔容和孔径
Table 3 Textural properties of the powder and honeycombed Fe-Ho-Mn/TiO2 catalysts
Entry Cataylyst Surface area A/(m2·g-1) Total pore volume v/(cm3·g-1) Average pore width d/nm 1 powder 95 0.28 12.0 2 honeycombed 83 0.24 13.7
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表 4 Fe-Ho-Mn/TiO2催化剂颗粒成型前后的NH3-TPD谱图
Table 4 NH3-TPD results of the powder and honeycombed Fe-Ho-Mn/TiO2 catalysts
Entry Catalyst NH3 desorption peak area weak(< 300 ℃) medium (300-500 ℃) strong (> 500 ℃) total 1 powder 6621 6539 6126 19286 2 honeycombed 4204 2005 1931 8140
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