Solid State NMR Spectroscopy Studies of the Nature of Structure Direction of OSDAs in Pure-Silica Zeolites ZSM-5 and Beta
Solid State NMR Spectroscopy Studies of the Nature of Structure Direction of OSDAs in Pure-Silica Zeolites ZSM-5 and Beta
复制标题
纯硅沸石 ZSM-5 和 Beta 中 OSDA 结构方向性质的固态核磁共振波谱研究
DOI：
10.1021/acs.jpcc.7b03350
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发表时间：
2017
影响因子：
3.7
通讯作者：
Luo Qing
中科院分区：
文献类型：
--
作者：
Liu Xiaolong;Luo Qing
TPA-OH-ZSM-5和TEA-OH-ZSM-5分子筛的2D 1H DQ-SQ NMR谱清楚地表明了骨架中的SiO-·HOSi氢键与TPA+和TEA+的烷基链之间的特定空间相关性。TPA-OH-ZSM-5分子筛的2D 1H DQ-SQ NMR谱表明，骨架中的SiO-··HOSi氢键在空间上与TPA+阳离子的甲基位置接近。对于TEA-OH-ZSM-5分子筛，2D 1H DQ-SQ NMR谱表明骨架中的SiO-··HOSi氢键在空间上与TEA+阳离子的甲基和亚甲基都很接近。这些结果表明，TPA+或TEA+阳离子对MFI骨架中的F阴离子、SiO-··HOSi氢键和T3+原子等负电荷中心的位置和分布有很强的静电相互作用。通过对可变接触时间1H-13 C CP/MAS NMR实验结果的分析，δ = 10.6ppm的13 C信号可归属于位于锯齿形通道中的TPA+阳离子的甲基，δ = 11.6ppm的13 C信号可归属于位于直通道中的TPA+阳离子的甲基。TEA-OH-Beta分子筛的2D 1 H DQ-SQ NMR和1H-13 C CP/MAS NMR谱表明，在ZSM-5中，骨架中的SiO-··HOSi氢键在空间上远离TEA+的烷基链，表明货车范德华力在沸石晶化过程中起主导作用。根据核磁共振的观察，可以推断OSDAs的结构方向的本质源于诱导期形成的无机-有机复合物中的货车范德华力和静电相互作用之间的复杂关系。
2D1H DQ-SQ NMR spectra of zeolites TPA-OH-ZSM-5 and TEA-OH-ZSM-5 clearly demonstrate the specific spatial correlations between the SiO–··HOSi hydrogen bonds within the framework and the alkyl chains of TPA+and TEA+. For zeolite TPA-OH-ZSM-5,the 2D1H DQ-SQ NMR spectrum shows that the SiO–··HOSi hydrogen bonds within the framework are spatially close to the methyl groups of TPA+cations. For zeolite TEA-OH-ZSM-5, the 2D1H DQ-SQ NMR spectrum shows that the SiO–··HOSi hydrogen bonds within the framework are spatially close to both the methyl and methylene groups of TEA+cations. These observations imply that the position and distribution of the negative charge centers such as F anions, SiO–··HOSi hydrogen bonds and T3+atoms in the MFI framework are influenced by TPA+or TEA+cations for the strong electrostatic interactions. By analyzing the variable contact time1H–13C CP/MAS NMR experimental results, the13C signal with δ = 10.6 ppm can be assigned to the methyl groups of TPA+cations located in zigzag channels and the13C signal with δ = 11.6 ppm can be assigned to the methyl groups of TPA+cations located in straight channels. Both 2D1H DQ-SQ NMR spectrum and1H–13C CP/MAS NMR spectra of TEA-OH-Beta show that the SiO–··HOSi hydrogen bonds within the framework are spatially further from the alkyl chains of TEA+in Beta than those in ZSM-5, which indicates that van der Waals interactions play the dominant roles during the crystallization process of zeolite Beta. According to our NMR observations, it can be inferred that the nature of structure direction of OSDAs roots in the complex relationship between van der Waals interactions and electrostatic interactions in the inorganic–organic composites formed in the induction period.