Density Functional Theory Study of the Dehydrogenation of Ethanol to Acetaldehyde over the Au-Exchanged ZSM-5 Zeolite: Effect of Surface Oxygen

详细信息    查看全文

• 作者：Thana Maihom ; Michael Probst ; Jumras Limtrakul
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：August 14, 2014
• 年：2014
• 卷：118
• 期：32
• 页码：18564-18572
• 全文大小：378K
• ISSN：1932-7455

文摘

The transformation of ethanol, one of the low-cost biomass products, into fine chemicals has received considerable attention related to the development of clean industrial technologies. We calculated the reaction mechanism of ethanol dehydrogenation to acetaldehyde over Au-exchanged ZSM-5 zeolite with and without surface oxygen by means of the density functional theory. The reaction is proposed to proceed in two steps. In the first, dissociation of the ethanol O鈥揌 bond leads to an ethoxide intermediate which is then converted to acetaldehyde. The reaction barrier for the first step is 9.0 kcal/mol for the Au鈥揙/ZSM-5 zeolite, much smaller than for the Au/ZSM-5 zeolite (43.0 kcal/mol). For step 2, the reaction barriers are 4.4 kcal/mol for Au鈥揙/ZSM-5 and 30.8 kcal/mol for Au/ZSM-5, respectively. The results indicate that the presence of surface oxygen on the Au site assists both the ethanol O鈥揌 bond dissociation and the conversion of ethoxide to acetaldehyde.