Characterization of [(CH3)3P−H]+ Complexes in Normal H-Y, Dealuminated H-Y, and H-ZSM-5 Zeolites Using 31P Solid-State NMR Spectroscopy
| Autor: | Hongjun Pan, Jack H. Lunsford, Baiyi Zhao |
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| Rok vydání: | 1999 |
| Předmět: | |
| Zdroj: | Langmuir. 15:2761-2765 |
| ISSN: | 1520-5827 0743-7463 |
| DOI: | 10.1021/la981170g |
| Popis: | Trimethylphosphine reacts with protons in acidic zeolites to form [(CH3)3P−H]+ complexes within the cavities and channels. The mobility of the protonated adduct strongly depends on the available space, which is a function of the amount of (CH3)3P in the zeolite and the size of the guest molecule relative to the cavity or channel dimensions. In an H-Y zeolite containing one molecule per large cavity, the motion is sufficiently rapid to average out a large P−H dipolar interaction, such that even in a static NMR experiment the lines due to JP-H coupling are well resolved. The motional rate is greater than 100 kHz. By contrast, the geometric constraints imposed by the smaller channels in ZSM-5, which are comparable in size to trimethylphosphine, severely restrict the motion. The chemical shift and J coupling values were determined for H-ZSM-5 and dealuminated H-Y zeolites, which are known to be strongly acidic, and for a normal H-Y zeolite, which is less acidic. The 31P chemical shift values were the same wit... |
| Databáze: | OpenAIRE |
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