Reactivity of isobutane on zeolites: a first principles study.
Reactivity of isobutane on zeolites: a first principles study.
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DOI：
10.1021/jp056707v
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发表时间：
2006-02
期刊：
影响因子：
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通讯作者：
Xiaobo Zheng;P. Blowers
中科院分区：
文献类型：
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作者：
Xiaobo Zheng;P. Blowers
本文采用从头算和密度泛函理论方法研究了分子筛催化的异丁烷质子裂解、一次氢交换、三次氢交换和脱氢反应。在B3 LYP/6- 31 G * 水平上对反应物、产物和过渡态结构进行了优化，并采用CBS-QB 3复合能方法计算了最终能量.计算的活化能垒为52.3千卡/摩尔的裂化，29.4千卡/摩尔的初级氢交换，29.9千卡/摩尔的叔氢交换，和59.4千卡/摩尔的脱氢。通过改变簇末端Si-H键长，研究了沸石酸性对反应垒的影响。提出了各反应的活化能垒与沸石脱质子能之间的解析表达式，从而可以准确地计算不同沸石催化剂的活化能垒。
In this work, ab initio and density functional theory methods are used to study isobutane protolytic cracking, primary hydrogen exchange, tertiary hydrogen exchange, and dehydrogenation reactions catalyzed by zeolites. The reactants, products, and transition-state structures are optimized at the B3LYP/6-31G* level, and the final energies are calculated using the CBS-QB3 composite energy method. The computed activation barriers are 52.3 kcal/mol for cracking, 29.4 kcal/mol for primary hydrogen exchange, 29.9 kcal/mol for tertiary hydrogen exchange, and 59.4 kcal/mol for dehydrogenation. The zeolite acidity effects on the reaction barriers are also investigated by changing the cluster terminal Si-H bond lengths. The analytical expressions between activation barriers and zeolite deprotonation energies for each reaction are proposed so that accurate activation barriers can be obtained when using different zeolites as catalysts.