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首页> 外文期刊>RSC Advances >A comparative computational study on the synthesis prescriptions, structures and acid properties of B-, Al- and G-incorporated MTW-type zeolites
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A comparative computational study on the synthesis prescriptions, structures and acid properties of B-, Al- and G-incorporated MTW-type zeolites

机译：B，Al和G结合的MTW型沸石的合成处方，结构和酸性质的比较计算研究

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摘要

The B-, Al- and Ga-incorporated H-, NH4-, Li-, Na- and K-forms MTW zeolites were comparatively studied to understand the crystallization thermochemistry, structure stabilities and acid properties using dispersion corrected density functional theory. Substitution energies were introduced to evaluate the synthesis prescriptions for MTW zeolites. The calculated results show that the trivalent and alkaline metal ions for the synthesis of the MTW zeolites are favored in the following order: Al > Ga > B and Na > K > Li > NH4 > H. The B-O, Si-O and O-H bonds have a covalent character while Al-O bonds show an obvious ionic character. However, the character of Ga-O bonds fall in between that of Al-O and B-O bonds. Introducing alkaline metal ions significantly changes the cell volumes. As a result, the cell volumes of the H- form B-, Al- and Ga-incorporated MTW zeolites are larger than Li- form, and smaller than K-form MTW zeolites. Further investigation of their properties show that the Bronsted acid sites of the zeolites follow the order of HAl-MTW > HGa-MTW > HB-MTW. The Lewis acidity of HB-MTW is similar to that of HAl-MTW, and weaker than that of HGa-MTW. These results are in good agreement with the previous experiments and provide new insights for the MTW zeolites.
机译：使用分散校正的密度泛函理论比较研究了掺有B，Al和Ga的H，NH4，Li，Na和K型MTW沸石，以了解其结晶热化学，结构稳定性和酸性质。引入取代能来评估MTW沸石的合成处方。计算结果表明，用于合成MTW沸石的三价和碱金属离子按以下顺序排列：Al> Ga> B和Na> K> Li> NH4>H。BO，Si-O和OH键具有共价特性，而Al-O键则具有明显的离子特性。然而，Ga-O键的特性介于Al-O和B-O键的特性之间。引入碱金属离子会显着改变细胞体积。结果，结合有H-型B-，Al-和Ga的MTW沸石的晶胞体积大于Li-型，并且小于K-形MTW沸石。对其性能的进一步研究表明，沸石的布朗斯台德酸性位点依次为HAl-MTW> HGa-MTW> HB-MTW。 HB-MTW的路易斯酸度与HAl-MTW相似，但比HGa-MTW弱。这些结果与先前的实验非常吻合，并为MTW沸石提供了新的见解。

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