Inhibition Mechanism of H2O on CO Oxidation Over CeMnOx Catalyst in Iron Ore Sintering Flue Gas

IF 2.3 4区化学 Q3 CHEMISTRY, PHYSICAL

Catalysis Letters Pub Date : 2024-07-09 DOI:10.1007/s10562-024-04733-8

Long Ding, Hexi Zhao, Lei Ni, Zhongbin Wang, Lixin Qian, Hongming Long

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Abstract

The emission of CO in sintering flue gas contributes to environmental pollution and energy wastage. Achieving full oxidation of CO presents a viable strategy for elevating the sintering flue gas temperature by over 50°C, thereby significantly reducing energy consumption during the heating of flue gas in NH₃-SCR denitrification systems. In this work, MnCeOx catalysts were synthesized under various conditions, including different calcination temperatures, durations, and molar ratios. Their catalytic activity and resistance to H₂O were evaluated under simulated sintering flue gas conditions at different temperatures. Our findings indicated that the M₈C₁ catalyst exhibited exceptional activity, achieving CO conversion rates exceeding 95% within 125–250°C. However, the catalytic activity experienced a notable decline during the H₂O resistance test at 150°C, while remaining unaffected at 250°C. Investigating the inhibition mechanism of H₂O on CO oxidation at varying temperatures through H₂-TPR, O₂-TPD, and in situ DRIFTS. At lower temperatures (150°C), CO and O₂ adsorption on the catalyst surface led to the formation of CO₂, with O₂ adsorption exerting a more significant influence on activity, consistent with the Langmuir–Hinshelwood mechanism. Introduction of H₂O into the flue gas resulted in the formation of OH⁻, which competed with CO and O₂ for adsorption on the catalyst surface, thereby diminishing catalyst oxidation activity due to competitive adsorption hindering CO and O₂ adsorption. Conversely, at higher temperatures (250°C), the reaction process between CO and lattice oxygen to produce CO₂ followed the Mars-van Krevelen mechanism. Notably, at these temperatures, no adsorbed OH⁻ were detected on the catalyst surface, leaving the activity unaffected. Based on our research, employing the MnCeOx catalyst during the high-temperature stage in conjunction with the NH₃-SCR catalyst is recommended for enhanced CO oxidation efficiency in sintering flue gas treatment processes.

Graphical Abstract

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铁矿烧结烟气中 H2O 对 CeMnOx 催化剂氧化 CO 的抑制机理

烧结烟气中 CO 的排放会造成环境污染和能源浪费。实现 CO 的完全氧化是将烧结烟气温度提高 50°C 以上的可行策略，从而显著降低 NH3-SCR 脱硝系统烟气加热过程中的能耗。在这项工作中，MnCeOx 催化剂是在不同条件下合成的，包括不同的煅烧温度、煅烧时间和摩尔比。在不同温度下的模拟烧结烟气条件下，对催化剂的催化活性和抗 H2O 能力进行了评估。研究结果表明，M8C1 催化剂具有优异的活性，在 125-250°C 的温度范围内，CO 转化率超过 95%。然而，在 150°C 的耐 H2O 试验中，催化活性明显下降，而在 250°C 时则不受影响。通过 H2-TPR、O2-TPD 和原位 DRIFTS，研究不同温度下 H2O 对 CO 氧化的抑制机制。在较低温度（150°C）下，CO 和 O2 在催化剂表面的吸附导致 CO2 的形成，其中 O2 的吸附对活性的影响更为显著，这与 Langmuir-Hinshelwood 机制一致。在烟气中引入 H2O 会形成 OH-，与 CO 和 O2 竞争吸附在催化剂表面，由于竞争吸附阻碍了 CO 和 O2 的吸附，从而降低了催化剂的氧化活性。相反，在较高温度（250°C）下，CO 和晶格氧生成 CO2 的反应过程遵循 Mars-van Krevelen 机理。值得注意的是，在这些温度下，催化剂表面未检测到吸附的 OH-，活性未受影响。根据我们的研究，建议在高温阶段将 MnCeOx 催化剂与 NH3-SCR 催化剂结合使用，以提高烧结烟气处理工艺中的 CO 氧化效率。图文摘要

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来源期刊

Catalysis Letters 化学-物理化学

CiteScore

5.70

自引率

3.60%

发文量

327

审稿时长

1 months

期刊介绍： Catalysis Letters aim is the rapid publication of outstanding and high-impact original research articles in catalysis. The scope of the journal covers a broad range of topics in all fields of both applied and theoretical catalysis, including heterogeneous, homogeneous and biocatalysis. The high-quality original research articles published in Catalysis Letters are subject to rigorous peer review. Accepted papers are published online first and subsequently in print issues. All contributions must include a graphical abstract. Manuscripts should be written in English and the responsibility lies with the authors to ensure that they are grammatically and linguistically correct. Authors for whom English is not the working language are encouraged to consider using a professional language-editing service before submitting their manuscripts.