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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Mechanism of F~- Elimination from Zeolitic D4R Units: A Periodic B3LYP Study on the Octadecasil Zeolite
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Mechanism of F~- Elimination from Zeolitic D4R Units: A Periodic B3LYP Study on the Octadecasil Zeolite

机译：沸石D4R单元消除F〜-的机理：十八碳沸石的定期B3LYP研究

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摘要

The mechanism of elimination of F" trapped inside the double four-membered ring (D4R) cages of octadecasil has been determined by means of periodic calculations at the B3LYP/VDZP//VTZP level of theory with the CRYSTAL06 program. Finite temperature and entropic effects are taken into account to study the efficiency of the elimination reaction, which is exothermic, requires acid media, and is catalyzed by cationic polar molecules with accessible protons, from which a hydronium ion has been considered in the present study. The mechanism consists of three steps that schematically correspond to hydrolysis of one SiOSi bridge in the D4R cage, extraction of the F~- from the unit, and recondensation of the bridge with formation of slightly adsorbed HF·H2O in the large cavity that can be easily eliminated by diffusion. The limiting step is the first one and involves a quite low Helmholtz free energy barrier even at 100 °C (51.6 kJ mol~(-1)) that slowly decreases with increasing temperature.
机译：通过使用CRYSTAL06程序在B3LYP / VDZP // VTZP理论水平上进行周期性计算，确定了消除十八烷基双四元环（D4R）笼中F“的机理。有限的温度和熵效应考虑到研究消除反应的效率，该反应是放热的，需要酸性介质，并且被具有可接近质子的阳离子极性分子催化，因此在本研究中考虑了水合氢离子，其机理包括三个方面这些步骤示意性地对应于D4R笼中一个SiOSi桥的水解，从单元中提取F〜-以及桥的缩合，从而在大空腔中形成了少量吸附的HF·H2O，可以很容易地通过扩散消除。限制步骤是第一步，即使在100°C（51.6 kJ mol〜（-1））时，其涉及的亥姆霍兹自由能势垒也相当低，其随温度升高而缓慢降低。

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