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Ab initio investigation of the relative stability of silicogermanates and their (Alumino)Silicates counterparts
Microporous and Mesoporous Materials ( IF 5.2 ) Pub Date : 2020-07-03 , DOI: 10.1016/j.micromeso.2020.110425
Elsy El Hayek , Bogdan Harbuzaru , Johan A. Martens , Céline Chizallet

The diversity of synthetic zeolites with silicogermanate composition has grown significantly. Many of these zeolites have large pores, thanks to the double 4-ring (d4r) structural subunits occupied by Ge atoms. The wide pores make them potentially interesting for catalytic transformation of bulky molecules, but the thermal and hydrothermal stability and the acidity are insufficient for practical applications. In the present work, the stability of known silicogermanate zeolite structures and their silicate and aluminosilicate analogues is evaluated using periodic density functional theory calculations. The thermodynamics of isomorphic substitution of Ge atoms for Si and Al via chemical processes are investigated. The study reveals that thermodynamically, (alumino)silicate counterparts of all known silicogermanates are intrinsically stable, and that the energetics of isomorphic substitution reactions of Ge atoms are almost independent of the distribution of d4r units in the different framework topologies. Chlorides are found better isomorphic substitution reagent candidates, at least theoretically. This work opens perspectives for the catalytic use of stable derivatives of silicogermanate zeolites.



中文翻译:

从头开始研究硅锗硅酸盐及其对应的(铝)硅酸盐

具有硅锗锗酸盐组成的合成沸石的多样性已显着增长。由于Ge原子占据的双4环(d4r)结构亚基,许多此类沸石具有大孔。宽大的孔隙使它们潜在地吸引了大分子的催化转化,但是热和水热稳定性以及酸度不足以用于实际应用。在目前的工作中,使用周期性密度泛函理论计算来评估已知的硅锗锗酸盐沸石结构及其硅酸盐和铝硅酸盐类似物的稳定性。研究了通过化学过程Ge原子同构取代Si和Al的热力学。研究表明,在热力学上,所有已知硅锗酸盐的(铝)硅酸盐对应物都是固有稳定的,Ge原子的同构取代反应的能量几乎与d4r单元在不同框架拓扑中的分布无关。至少从理论上讲,氯化物是更好的同构取代试剂候选物。这项工作为硅锗锗酸盐沸石稳定衍生物的催化应用开辟了前景。

更新日期:2020-07-22
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