Dong Wenbo, Zhao Qi, Zhao Jiancheng, Zhang Jiarong, Wang Yingxiong, Qiao Yan
State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, 27 South Taoyuan Road, Taiyuan, 030001, China.
Graduate University of Chinese Academy of Sciences, Beijing, 100049, China.
Magn Reson Lett. 2023 Dec 4;4(1):100091. doi: 10.1016/j.mrl.2023.11.003. eCollection 2024 Feb.
The aromatic compounds, including -xylene, -xylene, -xylene, and ethylbenzene, primarily originate from the catalytic reforming of crude oil, and have a wide variety of applications. However, because of similar physical and chemical properties, these compounds are difficult to be identified by gas chromatography (GC) without standard samples. With the development of modern nuclear magnetic resonance (NMR) techniques, NMR has emerged as a powerful and efficient tool for the rapid analysis of complex and crude mixtures without purification. In this study, the parameters of one-dimensional (1D) total correlation spectroscopy (TOCSY) NMR techniques, including 1D selective gradient TOCSY and 1D chemical-shift-selective filtration (CSSF) with TOCSY, were optimized to obtain comprehensive molecular structure information. The results indicate that the overlapped signals in NMR spectra of nonpolar aromatic compounds (including -xylene, -xylene, -xylene and ethylbenzene), polar aromatic compounds (benzyl alcohol, benzaldehyde, benzoic acid), and aromatic compounds with additional conjugated bonds (styrene) can be resolved in 1D TOCSY. More importantly, full molecular structures can be clearly distinguished by setting appropriate mixing time in 1D TOCSY. This approach simplifies the NMR spectra, provides structural information of entire molecules, and can be applied for the analysis of other structural isomers.
包括对二甲苯、间二甲苯、邻二甲苯和乙苯在内的芳香族化合物主要源自原油的催化重整，且有广泛的应用。然而，由于这些化合物具有相似的物理和化学性质，在没有标准样品的情况下，很难通过气相色谱法（GC）进行鉴别。随着现代核磁共振（NMR）技术的发展，NMR已成为一种强大而高效的工具，可用于快速分析复杂和未纯化的混合物。在本研究中，对一维（1D）全相关谱（TOCSY）NMR技术的参数进行了优化，包括1D选择性梯度TOCSY和带有TOCSY的1D化学位移选择性过滤（CSSF），以获得全面的分子结构信息。结果表明，在1D TOCSY中可以分辨出非极性芳香族化合物（包括对二甲苯、间二甲苯、邻二甲苯和乙苯）、极性芳香族化合物（苯甲醇、苯甲醛、苯甲酸）以及带有额外共轭键的芳香族化合物（苯乙烯）的NMR谱中的重叠信号。更重要的是，通过在1D TOCSY中设置适当的混合时间，可以清晰地区分完整的分子结构。这种方法简化了NMR谱，提供了整个分子的结构信息，并且可应用于其他结构异构体的分析。
