کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5367870 | 1388376 | 2008 | 5 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Methane activation over Ag-exchanged ZSM-5 zeolites: A theoretical study Methane activation over Ag-exchanged ZSM-5 zeolites: A theoretical study](/preview/png/5367870.png)
Methane activation catalyzed over Ag-exchanged ZSM-5 zeolites was investigated by using the density functional theory (DFT) with a cluster model. Two different pathways were taken into account in this work: the “alkyl” and the “carbenium” pathways. The activation barriers obtained are 34.09 and 66.63Â kcal/mol for the “alkyl” and the “carbenium” pathway, respectively. The calculated results show that the activation barrier of the “alkyl” pathway is smaller than that of “carbenium” pathway. Consequently, the “alkyl” pathway is the preferential reaction pathway. A new mechanism of methane conversion in the presence of ethene was proposed. In the catalytic cycle, the initial step of methane activation proceeds with the “alkyl” pathway and the Ag+ cation acts as an acceptor of the methyl group, then ethene reacts with the Ag+CH3â group to form propene. In addition, it is found that the Ag+ cations play an important role in the methane activation, compared with the reaction of methane activation over H-ZSM-5.
The reaction mechanism of methane activation over Ag-exchanged ZSM-5 zeolites was investigated by using density functional theory (DFT). The calculated results show that the “alkyl” pathway is the preferential reaction pathway. In addition, it is found that the Ag+ cations play an important role in the methane activation, compared with the reaction of methane activation over H-ZSM-5.
Journal: Applied Surface Science - Volume 254, Issue 16, 15 June 2008, Pages 4944-4948