MnOx?FeOy/TiO2?ZrO2?CeO2低溫選擇性催化還原NOz和抗毒性研究

張晴; 賀拴玲; 張錚; 汪莉

doi:10.13374/j.issn2095-9389.2019.11.05.002

MnO_x?FeO_y/TiO₂?ZrO₂?CeO₂低溫選擇性催化還原NO_z和抗毒性研究

doi: 10.13374/j.issn2095-9389.2019.11.05.002

張晴¹,
賀拴玲¹,
張錚²,
汪莉^1, ,

1.
北京科技大學能源與環境工程學院，北京 100083
2.
北京科技大學材料科學與工程學院，北京 100083

基金項目: 國家自然科學基金資助項目（u1560110）

詳細信息

通訊作者:
E-mail: wangli@ces.ustb.edu.cn

中圖分類號: TQ 032
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出版歷程
- 收稿日期: 2019-11-05
- 刊出日期: 2020-03-01

Low-temperature selective catalytic reduction of NO_z and anti-toxicity of MnO_x?FeO_y/TiO₂?ZrO₂?CeO₂

1.
School of Energy and Environment Engineering, University of Science and Technology Beijing, Beijing 100083, China
2.
School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China

More Information

Corresponding author: E-mail: wangli@ces.ustb.edu.cn

摘要

摘要: 用溶膠凝膠法制備TiO₂?ZrO₂?CeO₂（摩爾比4∶1∶1.25）載體，檸檬酸溶液浸漬法進一步負載MnO_x及MnO_x?FeO_y，進而合成了一種Fe摻雜的新型Mn基復合氧化物催化劑，考察其NH₃選擇性催化還原NO性能及抗硫性能。它在含硫氛圍中有良好的低溫選擇性催化還原（SCR）能力和抗中毒能力，Fe的引入促進了Mn與TiO₂?ZrO₂?CeO₂載體之間的相互作用，增加了催化劑表面Lewis酸性位點的數量。根據X射線光譜分析，Mn⁴⁺，Ce⁴⁺和吸附的氧的含量明顯增加，對提高催化劑的性能非常有利。根據熱重分析，在SO₂和H₂O同時存在的環境下，Fe的存在使硫酸銨和硫酸鈰的產生量減少，抑制了錳的硫酸化，進一步提高了催化劑的抗毒性。MnO_x（12.5%）?FeO_y（0.8）/TiO₂?ZrO₂?CeO₂（4∶1∶1.25）催化劑在180 ℃下，同時通入體積分數10% H₂O和125×10^?6 SO₂ 240 min，NO_z轉化率可保持在75.6%。根據研究成果，新型錳基復合金屬氧化物催化劑為進一步探索催化劑的SCR反應和抗毒機理提供了基礎，促進了SCR工藝的工業應用。
- MnO_x?FeO_y/TiO₂?ZrO₂?CeO₂ /
- 選擇性催化還原 /
- 氮氧化物 /
- 低溫 /
- 抗硫
Abstract: One of the most effective methods for the removal of NO_z from industrial flue gas is the technology known as low-temperature selective catalytic reduction (SCR). The main problem limiting the industrial application of catalysts is the need to improve their performances at low temperatures, and the fact that the anti-toxic mechanism of low-temperature denitration catalysts has yet to be explicitly identified. In this study, a TiO₂?ZrO₂?CeO₂ (molar ratio 4∶1∶1.25) carrier was prepared by the sol–gel method, and then loaded the active components MnO_x and MnO_x?FeO_y using the citric-acid-solution impregnation method to synthesize a new type of Fe-modified Mn-based multi-oxidation-state composite catalyst. The performance of this Mn-based composite oxide catalyst was investigated with respect to its NH₃-selective catalytic reduction of NO and sulfur resistance. The catalyst exhibits good low-temperature SCR redox ability and anti-poisoning ability in an SO₂-containing atmosphere, whereby the introduction of Fe promotes the interaction between Mn and the TiO₂?ZrO₂?CeO₂ (4∶1∶1.25) carrier, and increases the number of Lewis acid sites on the catalyst surface. According to the XPS analysis, the contents of Mn⁴⁺, Ce⁴⁺, and adsorbed oxygen are obviously increased, which is very advantageous for improving the performance of the catalyst. According to the thermogravimetric analysis, the introduction of Fe reduces the production of ammonium sulfate and ceric sulfate in the atmosphere containing SO₂ and H₂O, and inhibites the sulfation of manganese. The Fe element thereby increases the anti-toxic ability of the Mn-based multi-oxidation-state composite catalyst. By maintaining the MnO_x (12.5%)?FeO_y(0.8)/TiO₂?ZrO₂?CeO₂ (4∶1∶1.25) catalyst at 180 ℃, while continuously feeding 10% H₂O in volume fraction and 125×10^?6 SO₂ for 240 min, the NO_z conversion rate can be stably maintained at 75.6%. Based on the results of this work, a new type of Mn-based composite oxide catalyst has been developed that provides a foundation for further exploring the SCR reaction of the catalyst and its anti-toxic mechanism to promote the industrial application of the SCR process.
- MnO_x?FeO_y/TiO₂?ZrO₂?CeO₂ /
- selective catalytic reduction /
- nitrogen oxides /
- low temperature /
- sulfur resistance

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圖 1 催化劑的制備過程

Figure 1. Preparation of the catalyst

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圖 2 不同Fe/Mn摩爾比的催化劑性能測試圖. （a）活性測試圖；（b）抗硫性測試圖；（c）單獨加水對催化劑M（12.5%）?F（0.8）/TZCO的影響

Figure 2. Catalytic performance of the as-synthesized catalyst with different molar ratios of Fe and Mn: (a) activity test of catalysts; (b) sulfur resistance of catalysts; (c) NO_z removal rate of M(12.5%)?F(0.8)/TZCO by adding water alone

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圖 3 催化劑抗硫實驗前后的X射線衍射譜圖

Figure 3. XRD spectra of the catalyst before and after the sulfur experiment

a—TZCO (4:1:1.25); b—as-grown catalyst M(12.5%)-F(0.8)/TZCO; c—M(12.5%)?F(0.8)/TZCO after the sulfur-resistance experiment; d—as-grown catalyst M(12.5%)/TZCO; e—using M(12.5%)/TZCO after the sulfur-resistance experiment.

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圖 4 催化劑抗硫實驗前后的掃描電鏡分析譜圖. （a）抗硫前的M（12.5%）?F（0.8)/TZCO；（b）抗硫后的M（12.5%）?F（0.8）/TZCO；（c）抗硫前的M（12.5%）/TZCO；（d）抗硫后的M（12.5%）/TZCO

Figure 4. SEM characterizations of the catalysts before and after the sulfur-resistance experiment: (a) as-grown catalyst M(12.5%)?F(0.8)/TZCO; (b) MnO_x(12.5%)?F(0.8)/TZCO after the sulfur-resistance experiment; (c) as-grown catalyst M(12.5%)TZCO; (d) M(12.5%)/TZCO after the sulfur-resistance experiment

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圖 5 不同元素的X射線電子能譜擬合曲線. （a）Mn2p；（b）Ce3d；（c）Fe2p；（d）O1s（i和ii分別代表M（12.5%）/TZCO and M（12.5%）?F（0.8）/TZCO）

Figure 5. Fitting curves of XPS spectra with different elements: (a) Mn2p; (b) Ce3d; (c) Fe2p; (d) O1s (i and ii curves correspondingly representing the catalysts M(12.5%)/TZCO and M(12.5%)?F(0.8)/TZCO)

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圖 6 不同溫度下催化劑H₂程序升溫分析圖譜

Figure 6. H₂-TPR curves of the catalysts

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圖 7 不同溫度下MnO_x（12.5%）?FeO_y（0.8）/TiO₂?ZrO₂?CeO₂和MnO_x（12.5%）/TiO₂?ZrO₂?CeO₂催化劑的NH₃升溫脫附分析圖譜

Figure 7. NH₃-TPD curves of MnO_x(12.5%)?FeO_y(0.8)/TiO₂?ZrO₂?CeO₂ and MnO_x(12.5%)/TiO₂?ZrO₂?CeO₂ at different temperatures

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圖 8 不同溫度下不同催化劑抗硫反應前后的熱重譜圖. （a）M（12.5%）/TZCO；（b）M（12.5%）?F（0.8）/TZCO；（c）抗硫后M（12.5%）/TZCO及M（12.5%）?F（0.8）/TZCO

Figure 8. TG curves of the catalysts: (a) M(12.5%)/ TZCO; (b) M(12.5%)?F(0.8)/TZCO; (c) M(12.5%)/TZCO and M(12.5%)?F(0.8)/TZCO after sulfur resistance

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表 1 MnO_x(12.5%)/TiO₂?ZrO₂?CeO₂抗硫實驗前后的質量損失率

Table 1. Mass loss rates of MnO_x(12.5%)/TiO₂?ZrO₂?CeO₂ before and after the sulfur experiment

Mass loss stage	Mass loss ratio/%
Mass loss stage	Before sulfur experiment	After sulfur experiment	Difference
Stage A	1.010	1.212	0.202
Stage B	0.686	0.800	0.114
Stage C	1.502	3.387	1.885
Stage D	0.727	1.127	0.400
Total mass loss	3.925	6.526	2.601

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表 2 MnO_x(12.5%)?FeO_y(0.8) /TiO₂?ZrO₂?CeO₂抗硫實驗前后的質量損失率

Table 2. Mass loss rates of MnO_x(12.5%)?FeO_y(0.8) /TiO₂?ZrO₂?CeO₂ before and after the sulfur experiment

Mass loss stage	Mass loss ratio/%
Mass loss stage	Before sulfur experiment	After sulfur experiment	Difference
Stage A	1.378	1.503	0.125
Stage B	0.693	0.901	0.208
Stage C	1.194	2.649	1.455
Stage D	0.844	0.844	0.000
Total mass loss	4.109	5.897	1.788

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表 3 兩種催化劑抗硫實驗后的質量損失率對比

Table 3. Comparison of mass loss of two kinds of catalysts after the sulfur experiment

Mass loss stage	Mass loss ratio/%
Mass loss stage	M(12.5%)/TZCO	M(12.5%)?F(0.8) /TZCO	Difference
Stage A	0.202	0.125	0.077
Stage B	0.114	0.208	?0.094
Stage C	1.885	1.455	0.430
Stage D	0.400	0.000	0.400
Total mass loss	2.601	1.788	0.813

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