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观测了三种不同孔径磷酸镁铝分子筛样品MgAPO-5、MgAPO-11和MgAPO-34中~(27)Al和~(31)P核的魔角旋转核磁共振(MAS-NMR)谱,与AlPO_4-5、AlPO_4-11等磷酸铝分子筛样品的MAS-NMR谱相比较,证实分子筛中AlO_4或MgO_4四面体与PO_4四面体交替排列的结构特征。并进一步推断掺镁合成的磷酸铝分子筛(即磷酸镁铝)中,Mg离子进入了分子筛骨架,替代了骨架中的铝而不是磷。还根据~(31)P的MAS-NMR谱,确定了在磷酸镁铝分子筛中PO_4四面体的两种主要结构环境分别由4AlO_4或3AlO_4、MgO_4与之相接而成(表示为P(OAl)_4或P(OAl)_3(OMg))。并运用计算机拟谱,确定处于这两种环境中~(31)P的相对比率,从而求得分子筛骨架上磷、铝、镁的比率。
The magic angle nuclear magnetic resonance (MAS-NMR) spectra of ~ (27) Al and ~ (31) P nuclei in MgAPO-5, MgAPO-11 and MgAPO-34 samples of three kinds of MgO- -5, AlPO_4-11 and other aluminum phosphate molecular sieve samples MAS-NMR spectra compared to confirm the molecular sieve AlO_4 or MgO_4 tetrahedrons and PO 4 tetrahedrons alternately arranged structural features. And further inferred Mg-doped synthesis of aluminum phosphate molecular sieves (ie, magnesium aluminum phosphate), Mg ions into the framework of the molecular sieve, instead of the framework of aluminum instead of phosphorus. According to the MAS-NMR spectrum of ~ (31) P, it was confirmed that the two main structural environments of PO 4 tetrahedra in the magnesium aluminophosphate molecular sieve are connected by 4AlO 4 or 3AlO 4 and MgO 4 respectively (denoted by P (OAl) _4 or P (OAl) _3 (OMg)). The relative proportions of ~ (31) P in these two environments were determined by computerized pseudospectral analysis, and the ratios of phosphorus, aluminum and magnesium in the molecular sieve framework were obtained.