Dougnier F, Delmotte L, Guth J L
Laboratoire de Matériaux Minéraux, URA-CNRS 428, Université de Haute-Alsace, Ecole Nationale Supérieure de Chimie de Mulhouse, France.
Solid State Nucl Magn Reson. 1994 Nov;3(6):331-8. doi: 10.1016/0926-2040(94)90017-5.
Wide-band (1 MHz) 27Al magic-angle spinning nuclear magnetic resonance (MAS NMR) spectra were recorded for zeolite Y (Si/Al approximately 2.7) and high-silica (Si/Al approximately 3.8) FAU, EMT and mixed FAU-EMT structure-type zeolites synthesized using 15-crown-5 and/or 18-crown-6 ethers as templating agents. Spinning sidebands (related to first-order quadrupolar effects affecting satellite transitions) are observed in the spectra of the four calcined and fully rehydrated samples, reflecting a high symmetry of the framework aluminium atom surrounded by four oxygens. It is shown that the intensity of the spinning sidebands progressively increases after calcination and rehydration of the samples, indicating that the restoration of the high local order around the 27Al nuclei is rather slow. On the other hand, second-order quadrupolar interactions rapidly decrease upon rehydration of the calcined samples which is achieved within one day, as indicated by thermogravimetry. Some hypotheses are proposed to explain such a difference, and the role of water is also discussed.
使用15-冠-5和/或18-冠-6醚作为模板剂合成的Y型沸石（硅铝比约为2.7）、高硅（硅铝比约为3.8）FAU、EMT以及混合FAU-EMT结构类型的沸石，记录了宽带（1兆赫兹）27Al魔角旋转核磁共振（MAS NMR）光谱。在四个煅烧并完全再水化的样品的光谱中观察到了旋转边带（与影响卫星跃迁的一级四极效应有关），这反映了被四个氧包围的骨架铝原子具有高度对称性。结果表明，样品煅烧和再水化后，旋转边带的强度逐渐增加，这表明27Al核周围高局部有序性的恢复相当缓慢。另一方面，热重分析表明，煅烧样品再水化时，二级四极相互作用在一天内迅速降低。提出了一些假设来解释这种差异，同时也讨论了水的作用。
