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高交换度的BaX型分子筛用于吸附分离混合二甲苯。应用多晶X射线衍射方法研究了它的结构特点。晶胞参数a_0=25.000(5)(?)。分子筛中Ba~(2+)离子全部位于S(Ⅱ)位置上,在超笼内Ba~(2+)离子形成正四面体强静电场。具有高对称性的对位二甲苯在四面体电场里被牢固吸附,而具有较低对称性的邻、间位异构体在四面体电场内被吸附,但稳定性差。当脱附剂进入超笼,稳定性差的邻、间位二甲苯首先被脱附,然后在脱附剂浓度梯度的作用下对位二甲苯被脱附,实现了二甲苯邻、间、对异构体的分离。
High degree of exchange of BaX zeolite for the separation of mixed mixed xylene. The structural characteristics of polycrystalline X-ray diffraction were studied. Cell parameters a_0 = 25.000 (5) (?). The Ba ~ (2+) ions in the molecular sieve are all located at the S (Ⅱ) position, and the Ba ~ (2+) ions in the supercage form a positive tetrahedron strong electrostatic field. Paraxylene with high symmetry is firmly adsorbed in the tetrahedral electric field, while the ortho and meta isomers with lower symmetry are adsorbed in the tetrahedral electric field, but the stability is poor. When the desorbent enters the supercage and the stability is poor, the meta-xylene is firstly desorbed, and then the xylene is desorbed under the concentration gradient of the desorbent so as to realize the xylene-o-, m- and p- Separation of the structure.