Crystal Structures of Zeolite X Exchanged by Two Different Cations Structures of Cd32Cs28-X and Cd28Rb36-X (X = Si100Al92O384)

Bulletin of the Korean chemical society

Gyoung Hwa Jeong¹  Yang Kim¹ 

关键词: Structure;    Zeolite-X;    Cadmium;    Rubidium;    Cesium;   

DOI  :  

学科分类：化学（综合）

来源: Korean Chemical Society

【 摘 要 】

Two anhydrous crystal structures of fully dehydrated Cd²⁺ - and Cs⁺ -exchanged zeolite X, Cd₃₂Cs₂₈Si₁₀₀Al₉₂O₃₈₄ (Cd₃₂Cs₂₈-X: a = 24.828(11) �?) and fully dehydrated Cd,sup>2+ - and Rb⁺ -exchanged zeolite X, Cd₂₈Rb₃₆Si₁₀₀Al₉₂O₃₈₄ (Cd₂₈Rb₃₆-X: a = 24.794(2) �?), have been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at 21(1)�?. The structures were refined to the final error indices, R₁ = 0.058 and R₂ = 0.065 with 637 reflections for Cd₃₂Cs₂₈-X and R₁ = 0.086 and R₂ = 0.113 with 521 reflections for Cd₂₈Rb₃₆-X for which I > 3�?(�?). In the structure of Cd,sub>32Cs₂₈-X, 16 Cd²⁺ ions fill the octahedral sites I at the centers of the double six rings (Cd-O = 2.358(8)�? and O-Cd-O = 90.8(3)�? ). The remaining 16 Cd²⁺ ions occupy site �? (Cd-O = 2.194(8)�? and O-Cd-O = 119.7(4)�?) and six Cs⁺ ions occupy site �? opposite to the single six-rings in the supercage; each is 2.322�? from the plane of three oxygens (Cs-O = 3.193(13) and O-Cs-O = 73.0(2)�?). Aboutten Cs⁺ ions are found at site ケ`, 1.974�? into the sodalite cavity from their three oxygen plane (Cs-O = 2.947(8)�? and O-Cs-O = 80.2(3)�?). The remaining 12 Cs<sup>+</sup> ions are distributed over site ゲ` (Cs-O = 3.143(9) and O-Cs-O= 59.1(2)�?). In the structure of Cd₂₈Rb₃₆-X, 16 Cd²⁺ ions fill the octahedral sites I at the center of the double-sixrings (Cd-O = 2.349(15) and O-Cd-O = 91.3(5)�? ). Another 12 Cd²⁺ ions occupy two different II sites (Cd-O = 2.171(18)/2.269(17)�? and O-Cd-O = 119.7(7)/113.2(7)�?). Fifteen Rb⁺ ions occupy site �? (Rb-O = 2.707(17)�? and O-Rb-O = 87.8(5)�?). The remaining 21 Rb^{+ ions are distributed over site ゲ` (Rb-O = 3.001(16)�? and O-Rb-O = 60.7(4)�?). It appears that the smaller and more highly charged Cd2+ ions prefer sites I and �? in that order, and the larger Rb+ and Cs+ ions, which are less able to balance the anionic charge of the zeolite framework, occupy sites �? and ケ` with the remainder going to the least suitable site in the structure, site ゲ`.The maximum Cs+ and Rb+ ion exchanges were 30% and 39%, respectively. Because these cations are too largeto enter the small cavities and their charge distributions may be unfavorable, cation-sieve effects might appear.}

【 授权许可】

Unknown