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应用多晶X射线衍射法,研究了合成时以三乙胺为模板剂,晶粒维度为几个μm的AlPO_4-5分子筛结构,并经Rietveld法修正。对结构的测定得出,该分子筛的骨架几何构型与Bennett等报道的合成时以TPAOH为模板剂,晶粒维度为30×180μm,用单晶法测得的AlPO_4-5的结构相似,但骨架中T_1-O的平均间距上升为1.64(?)(T_1对应于Bennett文中的P)。T_2-O的平均间距下降为1.64(?)(T_2对应于Bennett文中的Al)。因此可得出骨架中T_1和T_2这二个位置均为P、Al无序地占有,从而破坏了分子筛在[001]方向的极性。另一方面,从结构的测定发现六方柱的中心可能成为具有高配位的阳离子位置。因此,AlPO_4-5型的结构允许存在Al/P≠1或Si部分取代P而造成带负电荷的骨架。
The polycrystalline X-ray diffraction method was used to study the structure of AlPO 4 -5 molecular sieve with triethylamine as a template and a grain size of several μm, which was modified by Rietveld method. The structure of the molecular sieve was found to have a geometrical configuration similar to that reported by Bennett et al. Using TPAOH as a template with a grain size of 30 × 180 μm. The structure of AlPO 4 -5 was similar to that of AlPO 4 -5 The average spacing of T_1-O in the framework increased to 1.64 (?) (T_1 corresponds to P in Bennett’s article). The average spacing of T_2-O decreased to 1.64 (?) (T_2 corresponds to Al in Bennett’s text). Therefore, it can be concluded that the two positions T_1 and T_2 in the framework are P and Al occupy in disorder, thus destroying the polarity of the molecular sieve in the direction of [001]. On the other hand, it was found from the structure determination that the center of the hexagonal column may become a cation site having a high coordination. Therefore, the AlPO_4-5 type structure allows the presence of Al / P ≠ 1 or partial replacement of P by Si resulting in a negatively charged framework.