物理化学学报 >> 2017, Vol. 33 >> Issue (8): 1589-1598.doi: 10.3866/PKU.WHXB201704142

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纳米自组装γ-Al2O3孔隙结构的核磁共振表征

王琳,肖立志*(),郭龙,廖广志,张岩,戈革   

  • 收稿日期:2017-03-01 发布日期:2017-06-14
  • 通讯作者: 肖立志 E-mail:xiaolizhi@cup.edu.cn; lizhi_xiao@fas.harvard.edu
  • 基金资助:
    国家自然科学基金(21427812);“111计划”(B13010)

Nuclear Magnetic Resonance Characterization of Nano Self-Assembly γ-Al2O3 Pore Structure

Lin. WANG,Li-Zhi. XIAO*(),Long. GUO,Guang-Zhi. LIAO,Yan. ZHANG,Ge. GE   

  • Received:2017-03-01 Published:2017-06-14
  • Contact: Li-Zhi. XIAO E-mail:xiaolizhi@cup.edu.cn; lizhi_xiao@fas.harvard.edu
  • Supported by:
    The project was supported by the National Natural Science Foundation of China(21427812);and the "111 Project" Discipline Innovative Engineering Plan, China(B13010)

摘要:

纳米自组装γ-Al2O3具有两种纳米级孔道,可作为适合于大分子扩散的催化剂载体,也可用于页岩气藏模型。表征纳米材料孔隙结构的方法有扫描电镜、氮吸附法及压汞法等,各有局限。本文利用核磁共振弛豫测量对纳米自组装γ-Al2O3孔隙结构进行研究和定量表征,并通过核磁共振实验和数值模拟对纳米自组装γ-Al2O3表面弛豫强度及孔径分布进行探索。结果表明,数值模拟核磁弛豫表征的纳米自组装γ-Al2O3的主体孔径为5-7 nm和30-42 nm,核磁弛豫实验通过误差函数法表征的主体孔径为5-9 nm和29-47 nm。相比于氮吸附仅表征微孔介孔及部分大孔,不能表征大于100 nm孔径,压汞法描述小于10 nm孔径相对不准确等问题,核磁弛豫能够全面表征2.8-315 nm纳米自组装γ-Al2O3的双峰孔隙系统。三个样品S-1、S-2、S-3的横向弛豫时间T2谱小孔大孔波峰的信号幅度比0.603、1.15、1.84直接反映各自的化学小孔大孔氧化铝投料比0.85、1.38、1.7的变化。建立的表征方法可以应用于页岩气微观结构和机理研究中,前景广阔。

关键词: 孔径分布, 核磁弛豫, 随机游走, 误差函数分析, 纳米自组装

Abstract:

Nano self-assembled γ-Al2O3, having two kinds of nano-scale pore structures, which can be used as a catalyst carrier suitable for large molecule diffusion and shale gas reservoir models. Characterization of the pore structures in nanomaterials are scanning electron microscopy, nitrogen adsorption method, mercury injection method, etc. These characterization techniques have their own limitations. This paper utilized nuclear magnetic resonance (NMR) relaxation measurements to study and quantitatively characterize the pore structures of nano self-assembled γ-Al2O3. Random walker simulation and error function analysis were used to explore the surface relaxation strength and pore size distribution of nano self-assembled γ-Al2O3. The random walker simulation results show that the main apertures of nano self-assembled γ-Al2O3 are 5-7 nm and 30-42 nm; NMR experiments through error function analysis show that the main apertures of the nano self-assembled material are 5-9 nm and 29-47 nm. Nitrogen adsorption only characterized the microporous, mesoporous, and part of the macroporous structures. The pore diameters greater than 100 nm cannot be detected by the nitrogen adsorption method. The mercury injection method characterizes apertures of size less than 10 nm relatively inaccurately. Nuclear magnetic relaxation can comprehensively characterize bimodal pore system of nano self-assembled γ-Al2O3 of size 2.8-315 nm. As one of the NMR measurements, the T2 spectrum signal amplitude ratio of three samples, S-1, S-2 and S-3 are 0.603, 1.15, 1.84, directly reflect the variety of their micropores and mesopores chemical Al2O3 material ratio 0.85, 1.38, 1.7 respectively. The suggested method can be applied to the investigation for shale gas pore structure and associated mechanisms.

Key words: Pore distribution, Nuclear magnetic relaxation, Radom walker, Error function analysis, Nano self-assambly

MSC2000: 

  • O646