核壳结构Co3O4@MnOx整体式催化剂的碳烟催化燃烧性能

徐大为; 张家琳; 高越; 李新刚

doi:10.19906/j.cnki.JFCT.2023057

核壳结构Co₃O₄@MnO_x整体式催化剂的碳烟催化燃烧性能

doi: 10.19906/j.cnki.JFCT.2023057

化学工程联合国家重点实验室天津化学化工协同创新中心天津市应用催化科学与工程重点实验室天津大学化工学院, 天津 300354

基金项目: 国家自然科学基金 (21878213)资助

详细信息

通讯作者:
Tel:13512925257, E-mail: xingang_li@tju.edu.cn

中图分类号: TQ448.21
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出版历程
- 收稿日期: 2023-06-25
- 修回日期: 2023-07-01
- 录用日期: 2023-07-03
- 网络出版日期: 2023-09-01
- 刊出日期: 2024-02-02

Catalytic soot combustion performance of core-shell Co₃O₄@MnO_x monolithic catalyst

State Key Laboratory of Chemical Engineering, Collaborative Innovation Center of Chemical Science and Engineering, Tianjin Key Laboratory of Applied Catalysis Science and Engineering, School of Chemical Engineering & Technology, Tianjin University, Tianjin 300354, China

Funds: The project was supported by National Natural Science Foundation of China (21878213)

摘要

摘要: 采用两步水热法在泡沫镍基底上合成了具有纳米棒形貌的 Co₃O₄@MnO_x 整体式催化剂，通过X射线衍射、X射线能谱分析、氢气-程序升温还原、X射线光电子能谱、拉曼光谱和碳烟-程序升温还原等手段对催化剂进行表征，在微型固定床反应器上评价了其催化碳烟燃烧性能，通过等温动力学实验探究了催化剂的本征活性。结果表明，Co₃O₄@MnO_x 催化剂呈现了以 Co₃O₄ 为核、以 MnO_x 为壳的核壳结构。与催化剂 Co-NW 相比，Co₃O₄@MnO_x 催化剂中 Co₃O₄ 与 MnO_x 之间的相互作用使其表面产生了更多高价物种 Mn⁴⁺ 和 Mn³⁺ 以及更多的表面氧空位，其氧化还原性能提高，催化剂的活性氧物种数量增加了两倍，催化性能得到改善，在 NO 存在的反应气氛中使碳烟起燃温度降低148 ℃。此外，相比催化剂 Co-NW，Co₃O₄@MnO_x 催化剂使碳烟燃烧反应的活化能从113.6 kJ/mol降低至102.2 kJ/mol，催化剂的本征活性提高了两倍。
- 碳烟燃烧 /
- 钴锰氧化物 /
- 整体式催化剂 /
- 核壳结构
Abstract: The Co₃O₄@MnO_x monolithic catalyst with nanorod morphology was synthesized on nickel foam by a two-step hydrothermal process and characterized by XRD, EDS-mapping, H₂-TPR, XPS, Raman and Soot-TPR. The catalytic soot combustion activities of the catalysts were investigated in a fixed-bed micro-reactor and the intrinsic activities of the catalysts were investigated by the isothermal kinetic experiments. The results reveal that the Co₃O₄@MnO_x catalyst shows a core-shell structure with Co₃O₄ as the core and MnO_x as the shell. Compared with Co-NW, there exist more high-valent state species of Mn⁴⁺ and Mn³⁺ and oxygen vacancies on the Co₃O₄@MnO_x catalyst surface due to the interaction between Co₃O₄ and MnO_x, which improve the redox performance of Co₃O₄@MnO_x. Compared with Co-NW, the active oxygen species amount of Co₃O₄@MnO_x is increased by two times, and Co₃O₄@MnO_x shows enhanced activity, which lowers the ignition temperature by 148 ℃ in the presence of NO. Also, compared with Co-NW, Co₃O₄@MnO_x decreases the activation energy of soot combustion reaction from 113.6 to 102.2 kJ/mol, and its intrinsic activity is increased by two times.
- soot combustion /
- cobalt and manganese oxides /
- monolithic catalysts /
- core-shell structure

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FIG. 2927. FIG. 2927.

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图 1 催化剂Co₃O₄@MnO_x的合成示意图

Figure 1 Schematic diagram of the synthesis of the Co₃O₄@MnO_x catalyst

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图 2 在10% O₂/N₂ （a）和6.0×10⁻⁴ NO/10% O₂/N₂ （b）气氛下催化剂的碳烟转化率

Figure 2 Soot conversion of the catalysts in (a) 10% O₂/N₂ and (b) 6.0×10⁻⁴ NO/10% O₂/N₂

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图 3 （a）催化剂Co₃O₄@MnO_x在催化碳烟燃烧过程中抗水性能；（b）催化剂 Co₃O₄@MnO_x在10% O₂/N₂气氛下经过5次Soot-TPO循环实验后的催化稳定性

Figure 3 (a) Effect of moisture on soot combustion over the Co₃O₄@MnO_x catalyst, and (b) Catalytic stability of the Co₃O₄@MnO_x in five Soot-TPO cycles in 10% O₂/N₂

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图 4 （a）催化剂的 XRD 谱图；（b）（a）的部分放大谱图

Figure 4 (a) The XRD patterns of the catalysts, and (b) zoom-in of (a)

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图 5 催化剂（（a1）–（a3））Co-NW和（（b1）–（b3））Co₃O₄@MnO_x的扫描电镜照片（（a1）和（b1））、透射电镜图（（a2）和（b2））和高分辨透射电镜照片（（a3）和（b3））；（c）催化剂Co₃O₄@MnO_x的TEM-EDS能谱图

Figure 5 SEM (a1 and b1), TEM (a2 and b2) and HRTEM ((a3) and (b3)) images of ((a1)–(a3)) Co-NW and ((b1)–(b3)) Co₃O₄@MnO_x, and (c) SEM-EDS elemental mapping images of the Co₃O₄@MnO_x

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图 6 催化剂的XPS谱图

Figure 6 XPS spectra of the catalysts （(a) Co 2p, (b) Mn 3s, (c) Mn 2p and (d) O 1s)

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图 7 整体式催化剂的H₂-TPR谱图

Figure 7 H₂-TPR profiles of the catalysts

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图 8 催化剂的Soot-TPR谱图

Figure 8 Soot-TPR profiles of the catalysts

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图 9 催化剂的Raman光谱谱图

Figure 9 Raman spectra of the catalysts

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图 10 催化剂在等温催化碳烟燃烧过程中厌氧阶段的CO₂浓度随时间的变化

Figure 10 CO₂ concentrations as a function of time over the catalysts before and after O₂ is removed from the reactant

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图 11 催化剂在等温碳烟燃烧反应中的阿伦尼乌斯曲线

Figure 11 Arrhenius plots of isothermal soot combustion

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表 1 在有/无6.0×10⁻⁴ NO存在时催化剂的碳烟燃烧活性

Table 1 Activities of the catalysts in the presence or absence of 6.0×10⁻⁴ NO for soot combustion

Catalyst	t₁₀/℃		t₅₀/℃		s_CO₂
Catalyst	0	6.0×10⁻⁴	0	6.0×10⁻⁴	0	6.0×10⁻⁴
Blank	475	447	562	542	55	60
Ni-foam	428	396	517	475	100	100
Co-NW	400	337	461	387	100	100
Co₃O₄@MnO_x	321	299	371	334	100	100

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表 2 松接触模式下，催化剂的碳烟燃烧活性

Table 2 Catalytic activities of catalysts for soot combustion in loose contact

Catalyst	Soot/catalyst weight ratio	Reaction gas	Characteristic temperature (t₅₀ or t_m)
Co₃O₄@MnO_x (this work)	1/10	10% O₂+6.0×10⁻⁴ NO	334
Co₃O₄-C^[10]	1/10	5% O₂+2.5×10⁻³ NO	421
K_0.1Co^[21]	1/9	8% O₂+5.0×10⁻⁴ NO	365
5KCo-NW*^[16]	1/10	5% O₂+6.0×10⁻⁴ NO	324
Mn₂O₃-C^[11]	1/10	5% O₂+2.5×10⁻³ NO	435
3DOM Mn_0.3Ce_0.7O_δ^[22]	1/10	5% O₂+2.0×10⁻³ NO	356
Mn₃O₄-HNS^[23]	1/10	5% O₂+2.5×10⁻³ NO	408
K-OMS-2/SiO₂-50^[24]	1/10	10% O₂+2.0×10⁻³ NO	328
K-Mn/3DOM La_0.8Ce_0.2FeO₃^[25]	1/9	5% O₂+5.0×10⁻⁴ NO	377
3DOMM PdCo₂O₄/CZO^[26]	1/9	5% O₂+2.0×10⁻³ NO	367
0.6Co/Fe-NF*^[27]	1/10	5% O₂+3.0×10⁻⁴ NO	382
*: These targets are monolithic catalysts.

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表 3 催化剂的元素含量和表面组成

Table 3 Elemental content and surface composition of the catalysts

Catalyst	Total Co/Mn ratio^a	Surface Co/Mn ratio^b	Co²⁺/ Co³⁺	O_ads/O_latt
Co₃O₄-NW	−	−	0.5	0.66
Co₃O₄@MnO_x	0.91	0.037	−	0.81
^a: Obtained by ICP；^b: Obtained by XPS.

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表 4 催化剂的反应速率、活性氧数量（O*）和 TOF 值

Table 4 The reaction rate, active oxygen (O*) amounts, and TOF of the catalysts

Catalyst	v/(mol·g⁻¹·s⁻¹)	O* amount/(mol·g⁻¹)	TOF/s⁻¹
Co-NW	4.7×10⁻⁷	5.6×10⁻⁵	8×10⁻⁴
Co₃O₄@MnO_x	1.95×10⁻⁶	1.15×10⁻⁴	1.7×10⁻³

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