以甲胺(MA)和二甲胺(DMA)为结构导向剂,在200℃加热摩尔组成为n(Al2O3):n(P2O5):n(R):n(H2 O)=1:1:1:277(R=MA,DMA)的混合物,分别得到了高结晶度的三维阴离子开放骨架磷酸铝AlPO4-53和AlPO4-21.质子化的甲胺和二甲胺分别位于AlPO4-53和AlPO4-21的骨架中以平衡骨架的负电荷.利用X射线粉末衍射分析、元素分析和液相酸碱度测量等表征手段,研究了2个合成体系的晶化过程以及晶化过程中液相的Al,P浓度和pH值随时间的演化.理论计算结果表明,质子化甲胺和二甲胺的N原子上的电荷分别为-0.263和-0.558 e(Mulliken),形式电荷密度分别为22.3和16.0 e/nm3,AlPO4-53和AlPO4-21的骨架电荷密度分别为-3.3和-3.1 e/nm3.结果表明,改变N原子的环境会影响其上的电荷量,从而改变有机胺的结构导向效应,有机胺的形式电荷密度和无机骨架电荷密度之间存在着匹配关系.%By heating the initial mixture with the molar composition of n ( Al2O3 ) : n ( P 2 O5 ) : n ( R ) :n(H2O)=1:1:1:277(R=methylamine or dimethylamine) at 200 ℃, highly crystalline three-dimensional anionic open-framework aluminophosphate of AlPO4-53 or AlPO4-21 was obtained. Protonated methylamine and dimethylamine were located in the framework of AlPO4-53 and AlPO4-21 to balance the negative charge of the framework, respectively. The crystallization processes of both initial mixtures were investigated by X-ray diffraction analysis(XRD), elemental analysis and pH measurement. Theoretical calculation shows that the charge on the N atom of protonated methylamine and dimethylamine is -0.263 and -0.558 e ( Mulliken ) , respectively. The corresponding formal charge density is 22.3 and 16.0 e/nm3 , respectively. The framework charge density of AlPO4-53 and AlPO4-21 is -3.3 and -3.1 e/nm3, respectively. These results indicate that the environment change around N atom can affect the amount of charge on it, which accordingly affects its structure-directing ability. A charge matching between the formal charge density of organic amines and the framework charge density was observed.
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