氧化镧催化甲烷氧化偶联反应的晶粒尺寸效应的研究

张祺; 牛鹏宇; 贾丽涛; 林明桂; 李德宝

doi:10.19906/j.cnki.JFCT.2022089

氧化镧催化甲烷氧化偶联反应的晶粒尺寸效应的研究

doi: 10.19906/j.cnki.JFCT.2022089

张祺^{1, 2,},
牛鹏宇^1,,
贾丽涛^1, ,,
林明桂^1, ,,
李德宝^{1, 3,}

1.
中国科学院山西煤炭化学研究所煤转化国家重点实验室，山西太原 030001
2.
中国科学院大学，北京 100049
3.
中国科学院洁净能源创新研究院，辽宁大连 116023

基金项目: 山西省基础研究计划(20210302124466)和中国科学院山西煤炭化学研究所创新基金(SCJC-DT-2022-06)资助

详细信息

通讯作者:
Tel: 0351-4040428, E-mail: jialitao910@163.com

linmg@sxicc.ac.cn

中图分类号: O643
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出版历程
- 收稿日期: 2022-09-09
- 修回日期: 2022-10-10
- 录用日期: 2022-10-16
- 网络出版日期: 2022-12-13
- 刊出日期: 2023-05-15

Study of grain size effect of lanthanum oxide catalyzed methane oxidation coupling reaction

ZHANG Qi^{1, 2
,},
NIU Peng-yu^1
,,
JIA Li-tao^{1
, ,},
LIN Ming-gui^{1
, ,},
LI De-bao^{1, 3
,}

1.
State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China
2.
University of Chinese Academy of Sciences, Beijing 100049, China
3.
Dalian National Laboratory of Clean Energy, Dalian 116023, China

Funds: The project was supported by the Basic Research Program of Shanxi Province (20210302124466) and the Innovation Fund Project by ICC CAS (grant SCJC-DT-2022-06).

摘要

摘要: 采用水热合成法，制备了不同晶粒尺寸的La₂O₃催化剂。运用XRD、原位拉曼光谱、原位红外漫反射光谱、H₂-TPR和O₂-TPD等表征手段研究了不同晶粒尺寸La₂O₃催化剂的OCM反应性能和催化剂之间的构效关系。结果表明，La₂O₃催化剂的La−O键会随着温度的升高出现明显的伸长，从而影响La₂O₃对O₂的吸附和动态储存。当晶粒尺寸增大至57.4 nm时，La₂O₃催化剂的储氧能力开始下降，同时伴随着表面氧物种，特别是超氧物种在催化剂表面富集，导致CH₄和产物的过度氧化，降低OCM反应的选择性。晶粒尺寸为52.3 nm的L-La₂O₃催化剂在750 ℃时，表面氧物种含量适宜，储氧能力强。在CH₄/O₂为3，空速为1.6 × 10⁵ mL/(g·h)的条件下表现出最佳的C_{2 +}烃选择性。
- 甲烷氧化偶联 /
- La₂O₃ /
- 晶粒尺寸 /
- 储氧能力
Abstract: La₂O₃ catalysts with different grain sizes were prepared under hydrothermal condition. The structure activity relationship of La₂O₃ catalysts with different grain sizes were investigated by using in-situ XRD, Raman, FT-IR and H₂-TPR, O₂-TPD. The results showed that the La−O bond of the La₂O₃ catalyst showed a significant elongation with increasing temperature, which affected its adsorption and dynamic storage of O₂. When increasing the grain size up to 57.4 nm, the oxygen storage capacity of the La₂O₃ catalyst started to decrease, accompanied by the enrichment of surface oxygen species, especially superoxide species, on the catalyst surface, which led to the over-oxidation of CH₄ and products and reduced the C_{2 +} hydrocarbons selectivity. The L-La₂O₃ catalyst with a grain size of 52.3 nm had a suitable content of surface oxygen species and a high oxygen storage capacity at 750 ℃. It exhibited the best C_{2 +} hydrocarbon selectivity up to a CH₄/O₂ of 3 and a vacancy rate of 1.6 × 10⁵ mL/(g·h).
- methane oxidation coupling /
- La₂O₃ /
- grain size /
- oxygen storage capacity

HTML全文

FIG. 2294. FIG. 2294.

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图 1 S-La₂O₃（（a）、（b））、M-La₂O₃（（c）、（d））、L-La₂O₃（（e）、（f））、XL-La₂O₃（（g）、（h））的SEM照片和颗粒尺寸分布

Figure 1 SEM photos and grain size distribution map of S- La₂O₃ ((a), (b)), M- La₂O₃ ((c), (d)), L- La₂O₃ ((e), (f)), XL- La₂O₃ ((g), (h))

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图 2 不同晶粒尺寸La₂O₃的XRD谱图

Figure 2 XRD patterns of La₂O₃ with different grain sizes

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图 3 不同晶粒尺寸La₂O₃的拉曼光谱谱图

Figure 3 Raman spectra of La₂O₃ with different grain sizes

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图 4 不同晶粒尺寸La₂O₃的原位拉曼光谱谱图

Figure 4 In-situ Raman spectra of La₂O₃ with different grain sizes (a): S-La₂O₃; (b): M-La₂O₃; (c): L-La₂O₃; (d): XL-La₂O₃

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图 5 不同晶粒尺寸La₂O₃催化OCM反应性能

Figure 5 OCM reaction performance of La₂O₃ with different grain sizes (a): CH₄ conversion; (b): O₂ conversion; (c): C_{2 +} hydrocarbon selectivity; (d): C_{2 +} hydrocarbon yield; (e): C_{2 +} hydrocarbon selectivity at 750 ℃

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图 6 不同晶粒尺寸的La₂O₃在相同O₂预处理温度下的H₂-TPR谱图

Figure 6 H₂-TPR image of La₂O₃ with different grain sizes under the same O₂ gas pretreatment temperature (a): O₂ pretreatment at 550 ℃; (b): O₂ gas pretreatment at 650 ℃; (c): O₂ gas pretreatment at 750 ℃

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图 7 La₂O₃催化剂在不同温度下体相内吸附氧的数量与晶粒尺寸的关系

Figure 7 Relationship between the amount of oxygen adsorbed in the bulk phase and grain size of La₂O₃ catalysts at different temperatures

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图 8 不同晶粒尺寸La₂O₃的O₂-TPD谱图

Figure 8 O₂-TPD profiles of La₂O₃ with different grain size

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图 9 不同晶粒尺寸La₂O₃在550和650 ℃，O₂处理30、75 s以及Ar吹扫600 s的原位红外光谱谱图

Figure 9 In situ infrared images (a) S-La₂O₃, (b) M-La₂O₃, (c) L-La₂O₃, and (d) XL-La₂O₃ of La₂O₃ with different grain sizes at 550 ℃ and 650 ℃ after 30 and 75 s of O₂ gas treatment

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表 1 催化剂的织构性质

Table 1 Texture properties of catalyst

Catalyst	A_BET/(m²·g⁻¹)^a	v_p/(cm³·g⁻¹)^b	d_p/nm^c	Crystallite size/nm^d
S-La₂O₃	9	0.07	29	42.5
M-La₂O₃	5	0.03	38	47.3
L-La₂O₃	3	0.02	41	52.3
XL-La₂O₃	4	0.02	40	57.4
^a: BET surface area. ^b: BJH desorption cumulative volum of pores. ^c: BJH desorption average pore diameter (4V/A). ^d: crystallite size was calculated by the Scherer formula based on the strongest diffraction (2θ=30°)

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表 2 不同温度下不同晶粒尺寸La₂O₃的拉曼峰偏移率

Table 2 Raman peak shift rates of La₂O₃ with different grain sizes at different temperatures

Catalyst	Raman shift/cm⁻¹					Drift rate/%^a
Catalyst	20 ℃	400 ℃	550 ℃	650 ℃	750 ℃	400 ℃	550 ℃	650 ℃	750 ℃
S-La₂O₃	407	397	392	391	388	2.5	3.7	3.9	4.7
M-La₂O₃	407	396	392	391	388	2.7	3.7	3.9	4.7
L-La₂O₃	407	398	394	392	389	2.2	3.1	3.7	4.4
XL-La₂O₃	406	396	393	390	387	2.5	3.2	3.9	4.7
^a: 400, 550, 650, 750 ℃ drift rate(%) = (20 ℃ Raman shift – 400, 550, 650, 750 ℃ Raman shift)100/20 ℃ Raman shift

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表 3 不同晶粒尺寸La₂O₃在不同O₂气预处理温度下吸附体相中近表层氧物种相对含量

Table 3 Relative content of oxygen species near surface oxygen species in bulk phase of La₂O₃ with different grain sizes at different O₂ gas pretreatment temperatures

Catalyst	Relative content of oxygen species in adsorbate phase/(μmol·g⁻¹)
Catalyst	550 ℃	650 ℃	750 ℃
S-La₂O₃	24	36	47
M-La₂O₃	29	45	51
L-La₂O₃	36	59	69
XL-La₂O₃	33	53	63

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