Pt-CeO<sub>2</sub>/ZSM-22催化正庚烷异构化反应性能研究

李子信; 郗宏娟; 陈晓燕; 马中义; 贾丽涛; 李德宝; 侯博

doi:10.19906/j.cnki.JFCT.2023031

Pt-CeO₂/ZSM-22催化正庚烷异构化反应性能研究

doi: 10.19906/j.cnki.JFCT.2023031

李子信^{1, 2,},
郗宏娟^1, ,,
陈晓燕^1,,
马中义^1,,
贾丽涛^1,,
李德宝^1,,
侯博^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: 山西省科技重大专项项目（202005D121002）和山西省重点研发计划（高新）项目（201903D121034）资助

详细信息

通讯作者:
Tel: 0351-4040428, E-mail: xhj20050314@sxicc.ac.cn

houbo@sxicc.ac.cn,

中图分类号: O643
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出版历程
- 收稿日期: 2023-03-03
- 修回日期: 2023-03-27
- 录用日期: 2023-04-10
- 网络出版日期: 2023-05-06

Performance study of Pt-CeO₂/ZSM-22 catalyzed n-heptane isomerization reaction

LI Zi-xin^{1, 2
,},
XI Hong-juan^{1
, ,},
CHEN Xiao-yan^1
,,
MA Zhong-yi^1
,,
JIA Li-tao^1
,,
LI De-bao^1
,,
HOU Bo^{1
, ,}

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 Science and Technology Major Project of Shanxi Province (202005D121002) and Key R&D Projects of Shanxi Province (201903D121034)

摘要

摘要: 结合浸渍法和物理混合法调控金属活性中心Pt的位点，使其单独落位到ZSM-22分子筛或氧化铈载体上，从而分别得到金属-酸双中心位点的间距达到原子级接触的Pt-ZSM-22/CeO₂催化剂和保持纳米级间距的Pt-CeO₂/ZSM-22催化剂。利用球差电镜、XRD、BET、H₂-TPR和XPS等手段，表征了两种催化剂的物化性质，并对其正庚烷异构化反应性能进行了研究。另外，考察了不同还原温度下Pt-CeO₂/ZSM-22催化剂的物化性质和反应性能变化。结果显示，金属-酸中心保持纳米级间距Pt-CeO₂/ZSM-22催化剂具有更高的正庚烷异构化活性和异构烃收率，这是由于Pt在CeO₂载体上呈原子级分散的原因。在Pt-CeO₂/ZSM-22催化剂还原过程中，CeO₂载体释放更多的氧空位有助于延缓金属Pt的聚集且有利于庚烷分子的吸附。当还原预处理温度为300 ℃时，庚烷转化率和庚烷异构烃收率分别为79.2%和75.4%，异构化选择性达到95.2%。
- 正庚烷 /
- 异构化 /
- 双功能催化剂 /
- 亲密度 /
- CeO₂
Abstract: A combination of impregnation and physical mixing methods was used to modulate the sites of the metal active center Pt, which were individually settled onto ZSM-22 molecular sieves or cerium oxide carriers, resulting in Pt-ZSM-22/CeO₂ catalysts with atomic-level contacts at the spacing of the metal-acid bicenter sites and Pt-CeO₂/ZSM-22 catalysts that maintained nanoscale spacing, respectively. The physical and chemical properties of the two catalysts were characterized by means of spherical differential electron microscopy, XRD, BET, H₂-TPR and XPS, and their n-heptane isomerization reaction performance was investigated. In addition, the changes of the physicochemical properties and reaction performance of Pt-CeO₂/ZSM-22 catalysts at different reduction temperatures were investigated. The results showed that the metal-acid center maintained nanoscale spacing Pt-CeO₂/ZSM-22 catalyst had higher n-heptane isomerization activity and isomeric hydrocarbon yield, which could be attributed to the atomic-level dispersion of Pt on the CeO₂ carrier. During the reduction of Pt-CeO₂/ZSM-22 catalyst, the release of more oxygen vacancies from the CeO₂ carrier helps to retard the aggregation of metal Pt and facilitates the adsorption of heptane molecules. When the reduction pretreatment temperature was 300 ℃, the heptane conversion and heptane isomerization hydrocarbon yield were 79.2% and 75.4%, respectively, and the isomerization selectivity reached 95.2%.
- n-heptane /
- isomerization /
- bifunctional catalyst /
- intimacy /
- CeO₂

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图 1 新鲜Pt-ZSM-22/CeO₂和 Pt-CeO₂/ZSM-22的XRD谱图

Figure 1 XRD spectra of fresh Pt-ZSM-22/CeO₂ and Pt-CeO₂/ZSM-22

a: ZSM-22; b: Pt-ZSM-22/CeO₂; c: Pt-CeO₂/ZSM-22

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图 2 新鲜Pt-ZSM-22/CeO₂和新鲜Pt-CeO₂/ZSM-22催化剂以及Pt-CeO₂的STEM图

Figure 2 STEM image of fresh Pt-ZSM-22/CeO₂ and Pt-CeO₂/ZSM-22 catalyst and Pt-CeO₂a: Pt-ZSM-22/CeO₂; b: Pt-CeO₂/ZSM-22; c: Pt-CeO₂

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图 3 不同温度还原后Pt-CeO₂样品的XRD谱图

Figure 3 XRD patterns of catalysts at different temperature reduction

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图 4 新鲜Pt-ZSM-22以及不同温度还原后Pt-CeO₂的TEM图

图a为新鲜Pt-ZSM-22样品，图b、c、d和e分别Pt-CeO₂经过为200、300、400和500 ℃还原后的样品

Figure 4 TEM image of fresh Pt-ZSM-22 samples and Pt-CeO₂ samples after reduction at different temperatures

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图 5 不同温度还原下Pt-CeO₂的H₂-TPR谱图

Figure 5 H₂-TPR spectra of Pt-CeO₂ samples at different temperature reductions

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图 6 不同温度还原后Pt-CeO₂的CO红外光谱谱图

Figure 6 CO chemisorption infrared spectra of Pt-CeO₂ samples reduced at different temperatures

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图 7 不同温度还原后Pt-CeO₂样品的 Pt 4f、O 1s和Ce 3d的XPS谱图

Figure 7 XPS spectra of Pt 4f, O 1s and Ce 3d of Pt-CeO₂ samples at different temperature reductions

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图 8 金属-酸双位点原子级接触Pt-ZSM-22/CeO₂和纳米级间距Pt-CeO₂/ZSM-22催化剂的庚烷异构化反应性能

Figure 8 Performance of metal-acid bidentate contact Pt-ZSM-22/CeO₂ and nanoscale spaced Pt-CeO₂/ZSM-22 catalysts for heptane isomerization reaction

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图 9 还原预处理温度对Pt-CeO₂/ZSM-22催化正庚烷异构化性能的影响

Figure 9 Effect of reduction pretreatment temperature on the performance of Pt-CeO₂/ZSM-22-catalyzed n-heptane isomerization

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表 1 两种催化剂的织构性质

Table 1 Texture properties of two types of catalysts

Sample	$S_{{\rm{BET}}}^{\rm{a}} /( {\rm{m}}^2 \cdot {\rm{g}}^{-1} ) $	$d_{{\rm{pore}}}^{\rm{b}} /{\rm{nm}}$	$v_{{\rm{pore}}}^{\rm{c}} /( {\rm{cm}}^3 \cdot {\rm{g}}^{-1} )$	$v_{{\rm{micro}}}^{\rm{d}} /( {\rm{cm}}^3 \cdot {\rm{g}}^{-1} )$
Pt-R-Z	196.0	5.9	0.29	0.06
Pt-Z-R	193.9	6.4	0.31	0.06
^a: BET surface area, ^b: average pore diameter, ^c: total pore volume, ^d: t-plot micropore volume

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表 2 不同温度还原预处理后Pt-CeO₂的织构性质

Table 2 Texture properties of samples after reduction pretreatment at different temperatures

Sample	$S_{{\rm{BET}}}^{\rm{a}} /({\rm{m}}^2 \cdot {\rm{g}}^{-1})$	$d_{{\rm{pore}}}^{\rm{b}} /{\rm{nm}} $	$v_{{\rm{pore}}}^{\rm{c}}/({\rm{cm}}^3 \cdot {\rm{g}}^{-1}) $	Pt /%^d
Pt-ZSM-22	–	–	–	0.83
Pt-CeO₂	23.3	19.9	0.12	0.79
Pt-CeO₂-H₂-200	22.3	19.1	0.11	-
Pt-CeO₂-H₂-300	22.2	18.1	0.10	–
Pt-CeO₂-H₂-400	24.7	18.2	0.11	–
Pt-CeO₂-H₂-500	23.8	18.5	0.11	–
^a: BET surface area, ^b: average pore diameter, ^c: total pore volume, ^d: determined by ICP

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