| 固体核磁共振结合密度泛函理论计算研究SSZ-39分子筛的钠离子落位与铝分布 |
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| 引用本文： | 陈翰迪,孔海宇,赵侦超,张维萍. 固体核磁共振结合密度泛函理论计算研究SSZ-39分子筛的钠离子落位与铝分布[J]. 波谱学杂志, 2021, 38(4): 543-551. DOI: 10.11938/cjmr20212906 |
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| 作者姓名： | 陈翰迪 孔海宇 赵侦超 张维萍 |
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| 作者单位： | 大连理工大学 化工学院 精细化工国家重点实验室, 辽宁 大连 116024 |
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| 基金项目： | 国家自然科学基金资助项目(21872017) |
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| 摘 要： | 具有AEI结构的SSZ-39分子筛的骨架外阳离子落位和铝分布对其催化性能影响显著.AEI笼中有三个结晶学不等价位，且铝取代T位具有一定的倾向性.本文结合固体核磁共振（NMR）技术（27Al/23Na MQ MAS NMR），以及密度泛函理论（DFT）计算，研究了不同硅铝比Na-SSZ-39分子筛中的Na+落位和铝分布.在孤立铝分布的情况下，铝原子优先占据于T3位，Na+主要落位于AEI笼中的SIIa0和SIII'a0位点上，其中SIII'a0位点的优先度较高，此外少部分Na+还落位于六棱柱内部的SIa0.当铝对存在时，AlSiSiAl分布的铝对占据六元环的对位（T3-T3），对应的Na+分别落位于SIIa1和SⅢ'a1位点.随着分子筛结构的部分破坏，游离的Na+可能形成明显的SIII'b位点.本文可加深对SSZ-39分子筛构效关系的理解，为更好地调控催化性能奠定基础.
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| 关 键 词： | 固体核磁共振 SSZ-39分子筛 铝分布 阳离子落位 密度泛函理论（DFT）计算 |
| 收稿时间： | 2021-04-11 |
Exploring the Na+ Locations and Al Distributions in SSZ-39 Zeolite by Solid-State NMR Spectroscopy and DFT Calculations |
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| CHEN Han-di,KONG Hai-yu,ZHAO Zhen-chao,ZHANG Wei-ping. Exploring the Na+ Locations and Al Distributions in SSZ-39 Zeolite by Solid-State NMR Spectroscopy and DFT Calculations[J]. Chinese Journal of Magnetic Resonance, 2021, 38(4): 543-551. DOI: 10.11938/cjmr20212906 |
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| Authors: | CHEN Han-di KONG Hai-yu ZHAO Zhen-chao ZHANG Wei-ping |
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| Affiliation: | State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, China |
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| Abstract: | The catalytic performance of zeolite SSZ-39 with AEI structure is significantly affected by the locations of its extra-framework cation and aluminum distributions. The AEI cage contains three crystallographically inequivalent T sites that tend to be substituted by aluminum. In this work, the Na+ locations and Al distributions in Na-SSZ-39 with different Si/Al ratios were studied by 27Al/23Na MQ MAS NMR spectroscopy together with density functional theory (DFT) calculations. For isolated Al substitution, the T3 site was found to be preferentially occupied by Al, and Na+ was mainly located in the 6-MR (SIIa0) or 8-MR (SIII'a0) sites of the AEI cage, although the priority of SIII'a0 site was slightly higher, and minor Na+ was located inside the hexagonal prism (SIa0). For paired Al substitution, stable AlSiSiAl structure was found to be located in 6-MR, and the corresponding Na+ cations were located at SIIa1 and SIII'a1 sites, respectively. In post-modified zeolites with partial destruction of the framework structure, some free Na+ cations were found to form distinct SIII'b sites. This study deepened the understanding on the structure-reactivity correlation of SSZ-39 zeolite and provided insights into how to fine-tune its catalytic performance. |
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| Keywords: | solid-state nuclear magnetic resonance SSZ-39 zeolite Al distribution cation location density functional theory (DFT) calculations |
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