NiO@SiO<sub>2</sub>核壳催化剂在浆态床中低温甲烷化研究

王辉; 张俊峰; 白云星; 王文峰; 谭猗生; 韩怡卓

NiO@SiO₂核壳催化剂在浆态床中低温甲烷化研究

王辉^{1, 2},
张俊峰^1, ,,
白云星^{1, 2},
王文峰^{1, 2},
谭猗生¹,
韩怡卓¹

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

基金项目: 中国-荷兰壳牌公司合作项目资助

详细信息

通讯作者:
张俊峰, Tel: 0351-4044388, E-mail: zhangjf@sxicc.ac.cn

中图分类号: O643
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- 被引次数: 0
出版历程
- 收稿日期: 2015-12-25
- 修回日期: 2016-02-29
- 网络出版日期: 2021-01-23
- 刊出日期: 2016-05-10

NiO@SiO₂ core-shell catalyst for low-temperature methanation of syngas in slurry reactor

WANG Hui^{1, 2},
ZHANG Jun-feng^{1
, ,},
BAI Yun-xing^{1, 2},
WANG Wen-feng^{1, 2},
TAN Yi-sheng¹,
HAN Yi-zhuo¹

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

Funds: The project was supported by China-Shell Global Solution International BV cooperation project

摘要

摘要: 采用改进的Stöber方法, 可控制备出具有不同形貌的NiO@SiO₂核壳结构催化剂, 并在浆态床反应器(320 ℃) 上, 对其合成气低温甲烷化性能进行评价; 同时借助XRD、TEM、XPS和N₂物理吸附等方法对反应前后催化剂的物化性质进行了表征。研究表明, 实验制备的催化剂形貌规整、粒径均匀, 且具有较好的热稳定性。在相同的制备条件下, 核颗粒粒径增大, 其SiO₂壳层的厚度随之增加。在反应过程中, 部分催化剂的核壳结构遭到破坏并出现SiO₂空壳, 是CO与壳层内的Ni作用生成易迁移的Ni羰基化物种(Ni (CO)_x) 所致。催化剂的甲烷化活性随着核颗粒粒径的增加呈现下降趋势; 在不同的反应阶段, 催化剂的失活速率存在明显差异, 在反应的前20 h内, 催化剂出现快速失活, 20 h后失活缓慢, 但是催化剂的甲烷选择性都保持在80%左右。催化剂的失活, 一方面, 是因为反应过程中, Ni核颗粒发生了长大; 另一方面, 是由于壳层中3-5 nm的介孔的减少以及催化剂比表面积、孔容的下降。
- 核壳 /
- Ni基催化剂 /
- 浆态床 /
- 低温甲烷化
Abstract: A series of NiO@SiO₂ core-shell catalysts were prepared using modified Stöber-method. Their catalytic performances in methanation of syngas were investigated in slurry reactor at 320 ℃. The catalysts before and after reaction were characterized by XRD, TEM, XPS, N₂-physisorption, etc. It was found that the NiO@SiO₂ core-shell samples had well-shape morphologies and relatively uniform scale. The catalyst test revealed that the methanation activity of these catalysts decreased dramatically with increase of core particle size. The three catalysts with distinct size of core and shell showed remarkably rapid deactivation in the initial period of 20 h and then deactivated slowly during the following reaction, while their CH₄ selectivity maintained at about 80%. Void-shell was formed during the reaction probably because easy-migrated Ni (CO)_x species were generated. Apparently, it was concluded that increase of core particle size, decrease of BET surface area and pore volume, and abatement of mesopores within 3-5 nm in the shell were responsible for the deactivation of these core-shell catalysts based on the characterization of catalysts.
- core-shell /
- nickel-based catalyst /
- slurry reactor /
- low-temperature methanation

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图 1 不同催化剂的反应性能

Figure 1 CO conversions and CH₄ selectivities as a function of time on stream over the different catalysts

■: NiO-350@SiO₂; ●: NiO-400@SiO₂; ▲: NiO-500@SiO₂; ▼: NiO-500/SiO₂

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图 2 不同温度焙烧处理得到的NiO纳米颗粒的XRD谱图

Figure 2 XRD patterns of NiO nano-particles calcined at different temperatures

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图 3 包覆前后不同NiO纳米颗粒的TEM照片及核壳尺寸分布

Figure 3 TEM images and size distributions of NiO nano-particles before and after encapsulation

(a): NiO-350; (b): NiO-400; (c): NiO-500; (d): NiO-350@SiO₂; (e): NiO-400@SiO₂; (f): NiO-500@SiO₂

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图 4 反应后NiO@SiO₂的TEM照片及核壳尺寸分布

Figure 4 TEM images, core size distribution and shell thickness of Ni@SiO₂ after reaction

(a): used NiO-350@SiO₂; (b): used NiO-400@SiO₂; (c): used NiO-500@SiO₂

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图 5 反应前后NiO@SiO₂的XPS谱图

Figure 5 XPS spectra of NiO@SiO₂ before and after reaction

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图 6 反应前(a) 和反应后(b) NiO@SiO₂颗粒的N₂吸脱附曲线，反应前(c) 和反应后(d) NiO@SiO₂颗粒的BJH孔分布

Figure 6 N₂ adsorption-desorption isotherms of NiO@SiO₂ particles before (a) and after (b) reaction, BJH pore size distribution of NiO@SiO₂ particles before (c) and after (d) reaction

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表 1 NiO颗粒粒径及反应前后NiO@SiO₂的核壳尺寸

Table 1 Particle size of NiO, core size and shell thickness of NiO@SiO₂

Sample	Core d/nm	Shell d/nm
NiO-350	4.9	-
NiO-350@SiO₂	5.1	6.1
Used NiO-350@SiO₂	8.1	5.0
NiO-400	8.1	-
NiO-400@SiO₂	8.6	11.2
Used NiO-400@SiO₂	10.6	10.1
NiO-500	23.7	-
NiO-500@SiO₂	23.3	23.0
Used NiO-500@SiO₂	27.8	20.6

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表 2 反应前后催化剂的表面原子浓度及体相Ni含量

Table 2 Surface atom concentration and Ni content of catalyst before and after reaction

Sample	Surface atomic concentrations^a/%			Ni/Si (atomic ratio)	Ni^b/%
Sample	Ni	Si	O	Ni/Si (atomic ratio)	Ni^b/%
NiO-350@SiO₂	10.11	17.77	72.12	0.57	57.32
Used NiO-350@SiO₂	9.85	17.12	73.03	0.58	55.92
NiO-400@SiO₂	8.50	24.36	67.14	0.35	58.98
Used NiO-400@SiO₂	5.09	27.73	67.18	0.18	61.21
NiO-500@SiO₂	6.46	21.22	72.32	0.30	60.68
Used NiO-500@SiO₂	4.61	28.38	67.01	0.16	63.14
Theoretical value^c	33.50	11.00	55.50	3.05	62.16
^a: the surface atomic concentrations of catalysts were calculated by XPS; ^b: Ni bulk concentration of catalysts obtained from ICP ^c: based on the addition mass when catalyst is prepared

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表 3 反应前后催化剂的N₂吸附

Table 3 N₂ sorption of NiO@SiO₂ before and after reaction

Sample	BET surface area A/(m²·g^-1)	Pore volume v/(cm³·g^-1)	Pore diameter d/nm
NiO-350@SiO₂	117.2	0.218	7.4
Used NiO-350@SiO₂	52.7	0.147	11.2
NiO-400@SiO₂	82.9	0.197	8.2
Used NiO-400@SiO₂	43.5	0.101	9.3
NiO-500@SiO₂	34.4	0.074	8.6
Used NiO-500@SiO₂	23.7	0.073	12.3

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