Understanding the co-effects of manganese and cobalt on the enhanced SCR performance for MnxCo1−xCr2O4 spinel-type catalysts,Catalysis Science & Technology

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Understanding the co-effects of manganese and cobalt on the enhanced SCR performance for MnxCo1−xCr2O4 spinel-type catalysts
Catalysis Science & Technology ( IF 4.4 ) Pub Date : 2020-07-01 , DOI: 10.1039/d0cy00872a
Erhao Gao _{1,

2,

3,

4,

5} , Bei Huang _{1,

2,

3,

4} , Zilong Zhao _{4,

6,

7,

8} , Hua Pan _{4,

6,

7,

8} , Wei Zhang _{1,

2,

3,

4,

5} , Younan Li _{1,

2,

3,

4,

5} , Matthew T. Bernards _{9,

10,

11,

12} , Yi He _{1,

2,

3,

4,

13} , Yao Shi _{1,

2,

3,

4,

5}

Affiliation

A novel ternary Mn_0.1Co_0.9Cr₂O₄ catalyst was identified from a range of chromium-based spinel-type (XCr₂O₄) oxides for the SCR of NO_x in coking flue gas. It exhibited a broad operating window (166–393 °C) under a gas hourly space velocity of 112 000 h⁻¹ with excellent H₂O and SO₂ durability. Compared to MnCr₂O₄ and CoCr₂O₄, the coexistence of Mn and Co cations in Mn_0.1Co_0.9Cr₂O₄ resulted in the enrichment of favorable Co³⁺, Mn⁴⁺, and Cr⁵⁺ species and oxygen vacancies, and enhanced Lewis acidity and redox ability. Mn and Co cations stably exist on the A²⁺ sites of Mn_xCo_1−xCr₂O₄ when x is less than 0.2, and the spinel-type structure preservation was conducive to their increased SCR activity. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed that both CoCr₂O₄ and Mn_0.1Co_0.9Cr₂O₄ followed the Langmuir–Hinshelwood mechanism, while higher amounts of adsorbed ammonia and nitrate species were produced on Mn_0.1Co_0.9Cr₂O₄, and the reaction rates were much higher. In addition, DFT demonstrated that the oxygen vacancy formation energy was lowered by Mn doping, and the enhanced affinity of NH₃ and NO with Mn_0.1Co_0.9Cr₂O₄ helps to form conducive NH₂ and nitrate species which facilitate the SCR reaction.

中文翻译：

了解锰和钴对MnxCo1-xCr2O4尖晶石型催化剂增强SCR性能的影响

从一系列铬基尖晶石型（XCr ₂ O ₄）氧化物中确定了一种新型三元Mn _0.1 Co _0.9 Cr ₂ O ₄催化剂，用于焦化烟气中的NO _x SCR 。在112 000 h ^-1的气体时空速下，它具有宽广的工作窗口（166–393°C），具有出色的H ₂ O和SO ₂耐久性。与MnCr ₂ O ₄和CoCr ₂ O _4相比，Mn _0.1 Co _0.9 Cr ₂ O ₄中Mn和Co阳离子共存导致富集有利的Co ³⁺，Mn ⁴⁺和Cr ⁵⁺物种和氧空位，并增强了路易斯酸度和氧化还原能力。当x小于0.2时，Mn和Co阳离子稳定地存在于Mn _x Co _1-_x Cr ₂ O ₄的A ²⁺位点上，并且尖晶石型结构的保存有利于其SCR活性的提高。原位漫反射红外傅里叶变换光谱（DRIFTS）显示，CoCr ₂ O ₄和Mn _0.1 Co _0.9 Cr ₂ O₄遵循Langmuir-Hinshelwood机理，而在Mn_0.1 Co_0.9 Cr₂ O₄上产生了大量的吸附氨和硝酸盐物种，并且反应速率更高。另外，DFT表明通过Mn掺杂降低了氧空位形成能，并且NH₃和NO与Mn_0.1 Co_0.9 Cr₂ O_4的亲和力增强有助于形成有利于SCR反应的有益NH₂和硝酸盐类。

更新日期：2020-07-21

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