摘要
应用晶格能极小化技术计算了二十一种高硅沸石的骨架晶格能，计算结果与二氧化硅致密相比较，发现这些高硅沸石彼此间的晶格能相差很小（＜３７ｋＪ／ｍｏｌ），与α石英相差３０～６７ｋＪ／ｍｏｌ．分析这些高硅沸石的ＸＲＤ数据发现，在它们的结构中包含很短的ＳｉＯ键长（０１４３１ｎｍ），很长的ＳｉＯ键长（０１８６２ｎｍ），ＳｉＯＯ键角分布范围大（７７５１～１３１８８°），ＯＳｉＳｉ键角平均在１５３°左右并且具有更大的分布范围（１２０～１８０°）．量子化学ＰＭ３计算结果表明，ＯＳｉＳｉ键角由１１４°变化至１８０°而引起的能量改变很小（仅１７４３ｋＪ／ｍｏｌ），当ＯＳｉＳｉ键角为１３５４°时能量最低．
The lattice energy of a series of high-silica zeolites was determined by using the lattice energy minimization method. Compared with the lattice energy of dense polymorphism of SiO_2, it is found that the difference in lattice energy among those high-silica zeolites is slight (<37 kJ/mol). All high-silica zeolite frameworks are only 30～67 kJ/mol less stable than αQuartz. The XRD data of the high-silica zeolites contain shorter SiO bond length (01431 nm), longer SiO bond length (0.1862 nm), and a large range of SiOO angles (77.51～13188°), an average OSiSi angle close to 153° and a larger range of OSiSi angle (120～180°). The results of PM3 molecular orbital calculation show that there is a small barrier (17.43 kJ/mol) to variation in the OSiSi angle between 114° and 180°, and there is the lowest energy for angle 135.4°.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
1998年第2期154-158,共5页
基金
国家攀登计划
国家自然科学基金
国家教委博士点基金
山东大学晶体化学国家重点实验室资助
关键词
高硅沸石
骨架结构
稳定性
结构
模拟计算
High-silica zeolite
Lattice energy minimization
Lattice energy
Bond length
Bond angle
Structure
Simulated calculation
