Mechanistic study of Mn/Ce co-doping for enhanced oxygen species conversion and catalytic combustion of dilute methane

doi:10.11949/0438-1157.20250482

Abstract

Abstract:

In this study, a series of Cu-based monolithic catalysts with different Mn/Ce doping ratios were synthesized and used for catalytic combustion activity testing of dilute methane. Among them, the 4Cu-3Mn-1Ce catalyst exhibited the best methane catalytic activity with a conversion of 85.0% at 550℃ and achieved complete conversion at 600℃. The mechanism of the effect of Mn/Ce doping on the physicochemical properties of Cu-based monolithic catalysts was investigated by characterization analysis, including in situ Fourier Transform infrared spectroscopy (in situ FTIR), and density functional theory (DFT) simulation calculations. The enhanced methane catalytic combustion activity of the Cu-based monolithic catalysts can be attributed to the following: Ce doping forming a Ce-Cu solid solution, weakening the Cu—O bond, and promoting lattice oxygen diffusion at high temperatures, thus enhancing high-temperature catalytic activity; and Mn doping promotes the adsorption of O₂ on the catalysts, which strengthens methane oxidation at low temperatures; Mn/Ce co-doping strengthens the activation of O₂ and its dissociation to *O, which fills the oxygen vacancies and regenerates into lattice oxygen, the co-doping strengthens the cycle of oxygen species and thus significantly improves the catalytic combustion activity of thin and dilute methane.

Key words: catalysis, methane, activation, combustion, doping

摘要：

合成了一系列具有不同Mn/Ce掺杂比例的Cu基整体式催化剂，并使用其进行了稀薄甲烷催化燃烧活性测试。其中，4Cu-3Mn-1Ce催化剂展现出最佳的甲烷催化活性，在550℃下转化率达85.0%，并且在600℃下实现了完全转化。利用包括原位红外光谱（in situ FTIR）在内的一系列表征分析与密度泛函理论（DFT）模拟计算探究了Mn/Ce掺杂对Cu基整体式催化剂理化性质的作用机制，Mn/Ce掺杂强化Cu基整体式催化剂稀薄甲烷催化燃烧活性可以归因为：Ce掺杂构建Ce-Cu固溶体，弱化Cu—O键合，促进高温下晶格氧的扩散，从而强化高温催化活性；Mn掺杂促进催化剂对O₂的吸附，强化低温下甲烷的催化活性；Mn/Ce共掺杂强化O₂活化并解离为*O，*O填补进入氧空位再生为晶格氧，共掺杂强化了氧物种循环，从而显著提高稀薄甲烷催化燃烧活性。

关键词: 催化, 甲烷, 活化, 燃烧, 掺杂

CLC Number:

TQ 426.83

Jiaqi QIU, Zhongqing YANG, Zhigang ZHANG, Hailong GAN, Chunxiu HUO, Zhishuai DOU, Jingyu RAN. Mechanistic study of Mn/Ce co-doping for enhanced oxygen species conversion and catalytic combustion of dilute methane[J]. CIESC Journal, 2025, 76(11): 5604-5616.

邱家齐, 杨仲卿, 张志刚, 甘海龙, 霍春秀, 窦志帅, 冉景煜. Mn/Ce共掺杂强化氧物种转化与稀薄甲烷催化燃烧机制研究[J]. 化工学报, 2025, 76(11): 5604-5616.

Figures/Tables 13

Fig.1 Experimental test system for catalytic combustion of dilute methane

Fig.2 (a) Catalytic activity test of samples with different Mn/Ce doping ratios; (b) Catalytic activity of 4Cu-3Mn-1Ce for different initial concentrations of methane

Table 1 Characteristic temperatures of samples with different Mn/Ce doping ratios

序号	催化剂种类	T₁₀/℃	T₅₀/℃	T₉₀/℃
1	8 Cu	459.1	541.9	619.9
2	4Cu-4Mn	419.8	515.9	584.9
3	4Cu-3Mn-1Ce	404.8	513.1	558.1
4	4Cu-2Mn-2Ce	418.6	520.6	574.9
5	4Cu-1Mn-3Ce	424.4	520.6	571.9
6	4Cu-4Ce	427.7	520.6	573.2

Fig.3 (a) 4Cu-3Mn-1Ce sample stability test; (b) Cyclic stability of samples after stability testing

Fig.4 SEM and EDS images of samples

Fig.5 XRD patterns of samples with different Mn/Ce doping ratios

Fig.6 XPS spectra of O 1s orbitals of samples with different Mn/Ce doping ratios

Table 2 Distribution of O species content in samples with different Mn/Ce doping ratios

样品	含量/%
样品	O_latt	O_sur	O_ads
4Cu-4Ce	22.5	34.1	43.4
4Cu-4Mn	10.8	32.2	57.0
4Cu-3Mn-1Ce	19.0	44.0	37.0

Fig.7 (a) O2-TPD spectra of samples with different Mn/Ce doping ratios; (b) EPR spectra of samples before and after Ce doping; (c) XPS spectra of Cu 2p orbitals of samples with different Mn/Ce doping ratios

Fig.8 (a) Enhancement of O2 adsorption energy by Mn doping; (b) PDOS analysis of O2 adsorption on Cu-O and Cu-Mn-O

Table 3 Distribution of Cu species content in samples with different Mn/Ce doping ratios

样品	含量/%
样品	Cu⁺	Cu²⁺
4Cu-4Ce	9.0	91.0
4Cu-4Mn	16.9	83.1
4Cu-3Mn-1Ce	14.7	85.3

Fig.9 In situ FTIR spectra of 4Cu-3Mn-1Ce reacting in an oxygen-rich atmosphere (3% methane, 21% O2, remainder N2) and an oxygen-deficient atmosphere (3% methane, remainder N2) at 450℃

Fig.10 Enhanced mechanism of CH4 catalytic combustion on the surface of Cu-Mn-Ce catalysts

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