Zibrowius B, Lohse U
UMIST, Department of Chemistry, Manchester, UK.
Solid State Nucl Magn Reson. 1992 Jul;1(3):137-48. doi: 10.1016/0926-2040(92)90014-z.
AlPO4-17 and SAPO-17 in their as-synthesized, calcined, and calcined and subsequently rehydrated forms have been studied by 27Al and 31P MAS NMR. Pronounced structural changes caused by template removal and rehydration can unambiguously be attributed to a change in the coordination number (on calcination: 5-->4, on rehydration/dehydration: 4<-->6) of part of the framework aluminium atoms. The different resonance lines can be assigned to crystallographically inequivalent sites present in the modified ERI framework. 27Al quadrupolar coupling parameters of the two aluminium sites in the calcined AlPO4-17 (CQ = 4.4 MHz and 2.1 MHz) were determined by recording spectra at different field strengths. The isotropic chemical shifts were obtained from rotation sidebands of the (+/- 3/2, +/- 1/2) satellite transitions. 2D 27Al nutation MAS NMR was used to corroborate the line assignment for the as-synthesized and the rehydrated AlPO4-17. By using 13C MAS NMR it was shown that the occluded template (cyclohexylamine) is present as ions. For the first time, a splitting of the 29Si NMR line caused by crystallographically inequivalent sites in a SAPO-type material is reported. The line splitting of 4.3 ppm is comparable with that observed for isostructural aluminosilicate erionite.
通过27Al和31P MAS NMR对AlPO4 - 17和SAPO - 17的合成态、煅烧态以及煅烧后再水合态进行了研究。模板去除和再水合引起的明显结构变化可明确归因于部分骨架铝原子配位数的变化（煅烧时：5→4，再水合/脱水时：4⇄6）。不同的共振线可归属于改性ERI骨架中存在的晶体学不等价位点。通过在不同场强下记录光谱，确定了煅烧后的AlPO4 - 17中两个铝位点的27Al四极耦合参数（CQ = 4.4 MHz和2.1 MHz）。各向同性化学位移是从（±3/2，±1/2）卫星跃迁的旋转边带获得的。二维27Al章动MAS NMR用于证实合成态和再水合态AlPO4 - 17的谱线归属。通过13C MAS NMR表明，包藏的模板（环己胺）以离子形式存在。首次报道了SAPO型材料中由晶体学不等价位点引起的29Si NMR谱线分裂。4.3 ppm的谱线分裂与同结构的铝硅酸盐毛沸石中观察到的分裂相当。
