Cr-MIL-101介导的纳米Cr<sub>2</sub>O<sub>3</sub>高效催化正己烷脱氢反应研究

李修仪; 申浩伟; 徐家乐; 李春义

doi:10.1016/S1872-5813(24)60458-5

Cr-MIL-101介导的纳米Cr₂O₃高效催化正己烷脱氢反应研究

doi: 10.1016/S1872-5813(24)60458-5

中国石油大学(华东) 重质油国家重点实验室, 山东青岛 266580

基金项目: 山东省重点研发计划(2021ZLGX06)资助

详细信息

通讯作者:
Tel: 0532-86981862, E-mail: chyli@upc.edu.cn

中图分类号: TQ519
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- 被引次数: 0
出版历程
- 收稿日期: 2024-03-19
- 修回日期: 2024-05-05
- 录用日期: 2024-05-06
- 网络出版日期: 2024-06-05

Cr-MIL-101 derived nano-Cr₂O₃ for highly efficient dehydrogenation of n-hexane

State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266580, China

Funds: Theproject was supported by Key R &D Program of Shandong Province(2021ZLGX06).

摘要

摘要: 通过热解大比表面Cr-MIL-101制备纳米Cr₂O₃（n-Cr₂O₃），考察其催化正己烷脱氢反应性能，并比较与沉淀法p-Cr₂O₃-1、焙烧铬盐得到的p-Cr₂O₃-2以及工业Cr₂O₃/Al₂O₃催化正己烷脱氢活性差异。n-Cr₂O₃能够催化正己烷高效脱氢为己烯和苯，并且其催化脱氢活性与焙烧温度有关。600 ℃焙烧的n-Cr₂O₃催化正己烷脱氢转化率最高40.6%，对产物己烯和苯的选择性分别为20.1%和69.3%。提高焙烧温度，n-Cr₂O₃催化正己烷脱氢活性下降但稳定性增强，催化剂积炭量减少。p-Cr₂O₃-1和p-Cr₂O₃-2催化正己烷脱氢转化率很低（<7.5%），比活性分别为1.5和1.7 g/(m²·h)，低于n-Cr₂O₃-600的（2.0 g/(m²·h)）。通过BET、XRD、TEM和FT-IR等表征发现，n-Cr₂O₃为具有较大比表面的纳米颗粒（10−20 nm），多暴露晶面和脱氢活性位，而p-Cr₂O₃是比表面非常小的大颗粒，所暴露脱氢活性位少。相比之下，Cr₂O₃/Al₂O₃催化剂由于大比表面Al₂O₃的分散作用，催化正己烷脱氢效率更高（2.4 g/(m²·h)）。因此，由Cr-MIL-101焙烧得到的n-Cr₂O₃催化正己烷脱氢的高活性源于这种纳米Cr₂O₃所具有的独特性质：小颗粒，大比表面，多暴露活性位。
- 正己烷 /
- 脱氢 /
- 己烯 /
- 苯 /
- 纳米Cr₂O₃
Abstract: Nano-Cr₂O₃ (n-Cr₂O₃) was prepared by calcining the mesoporous Cr-MIL-101, and the catalytic performance for n-hexane dehydrogenation was investigated. It was found that dehydrogenation of n-hexane on n-Cr₂O₃ can produce n-hexenes and benzene efficiently, and the catalytic performance is related to the calcination temperature. The optimal n-hexane conversion can be obtained on n-Cr₂O₃-600, is 40.6%, and the selectivities to n-hexenes and benzene are 20.1% and 69.3%, respectively. Increasing the calcination temperature, the conversion of n-hexane is decreased while the stability is enhanced. The n-hexane conversion of p-Cr₂O₃-1 (obtained by precipitation method) and p-Cr₂O₃-2 (obtained by calcinating Cr(NO₃)·9H₂O directly) catalysts are relative low (<7.5%), and their specific activity for n-hexane dehydrogenation are 1.5 and 1.7 g/(m²·h), respectively, lower than that of n-Cr₂O₃-600 (2.0 g/(m²·h)). The results of BET、XRD、TEM and FT-IR reveal that n-Cr₂O₃ is the nanoparticle with large specific surface area that more crystal planes and dehydrogenation active sites are exposed, while p-Cr₂O₃ is the large particle with extremely low surface area that the dehydrogenation active sites are less exposed. By contrast, industrial Cr₂O₃/Al₂O₃ catalyst possesses high specific activity of 2.4 g/(m²·h) due to the dispersion effect of Al₂O₃. Therefore, the highly catalytic activity of n-Cr₂O₃ for n-hexane dehydrogenation is attributed to the unique properties of n-Cr₂O₃: small particle, large specific surface area and more exposed active sites. This work not only explains the highly dehydrogenation performance of nano-Cr₂O₃ derived by Cr-MIL-101, but also provides guidance for the precise design and synthesis of high-performance CrO_x-based catalyst for the dehydrogenation of alkanes.
- n-hexane /
- dehydrogenation /
- n-hexenes /
- benzene /
- nano-Cr₂O₃

HTML全文

图 1 Cr-MIL-101样品的XRD谱图（a）红外光谱谱图（b）N₂吸附-脱附等温曲线（c）和热重（d）谱图

Figure 1 XRD (a), FT-IR (b), N₂ adsorption/desorption isotherms (c) and TG (d) profiles of Cr-MIL-101

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图 2 Cr₂O₃催化剂的低温N₂吸附-脱附等温曲线

Figure 2 N₂ adsorption/desorption isotherms of Cr₂O₃ catalysts

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图 3 Cr₂O₃催化剂的XRD谱图

Figure 3 XRD profiles of Cr₂O₃ catalysts

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图 4 Cr₂O₃催化剂的TEM图像

Figure 4 TEM images of Cr₂O₃ catalysts

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图 5 Cr₂O₃催化剂的红外光谱谱图

Figure 5 FT-IR spectra of Cr₂O₃ catalysts

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图 6 Cr₂O₃催化剂的XPS Cr 2p谱图

Figure 6 XPS spectra of Cr 2p for Cr₂O₃ catalysts

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图 7 不同焙烧温度n-Cr₂O₃催化正己烷脱氢转化率（a），己烯选择性（b），苯选择性（c）和反应3 h焦炭量（d）

Figure 7 n-Hexane dehydrogenation behavior of n-Cr₂O₃ with different calcination temperature: conversion of n-hexane (a), selectivity to n-hexenes (b), selectivity to benzene (c) and coke content (d)

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图 8 不同Cr₂O₃催化正己烷脱氢反应转化率和比活性对比

Figure 8 Comparison of n-hexane conversion and specific activity for different Cr₂O₃ catalysts.

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表 1 Cr₂O₃催化剂的织构性质

Table 1 Textural properties of Cr₂O₃ catalysts

Sample	S_BET/(m²·g⁻¹)	v_pore/(cm³·g⁻¹)	D_pore/nm
n-Cr₂O₃-600	62.5	0.28	16.4
n-Cr₂O₃-700	57.0	0.22	18.3
n-Cr₂O₃-800	39.1	0.14	17.4
n-Cr₂O₃-950	13.4	0.09	19.7
p-Cr₂O₃-1	5.2	0.03	26.1
p-Cr₂O₃-2	6.1	0.03	33.5
Cr₂O₃/Al₂O₃	117.5	0.21	4.9

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表 2 常压、不同温度下正己烷脱氢为单己烯热力学平衡数据

Table 2 Thermodynamic equilibrium data for n-hexane dehydrogenation to n-hexenes at different temperatures

t/℃	△G/(kJ·mol⁻¹)	K_e	Equilibrium conversion/%
400	165.75	1.57×10⁻²	11.76
450	133.55	6.64×10⁻²	22.66
500	96.85	0.27	40.36
550	66.65	0.80	57.88
600	30	2.33	75.51

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表 3 反应1 h时不同焙烧温度n-Cr₂O₃催化正己烷脱氢反应

Table 3 Catalytic results of n-Cr₂O₃ catalyst for n-hexane dehydrogenation at TOS of 1 h

Sample	n-Cr₂O₃-600	n-Cr₂O₃-700	n-Cr₂O₃-800	n-Cr₂O₃-950
Conversion of n-C₆H₁₄/%	40.6	37.8	22.8	11.3
Selectivity to product/%
n-C₆H₁₂	20.1	21.5	25.1	28.2
C₆H₆	69.3	68.1	64.4	60.6
2,4-C₆H₁₀	2.9	3.0	3.1	3.2
Cracking products	3.2	2.9	2.8	2.9
Isomerization products	2.8	2.9	2.9	3.0
Others	1.7	1.6	1.7	2.1

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