Insight into the Effect of Promoter Mn on Ethanol Formation from Syngas on a Mn-Promoted MnCu(211) Surface: A Comparison with a Cu(211) Surface

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• 作者：Riguang Zhang ; Guiru Wang ; Baojun Wang ; Lixia Ling
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：March 13, 2014
• 年：2014
• 卷：118
• 期：10
• 页码：5243-5254
• 全文大小：798K
• 年卷期：v.118,no.10(March 13, 2014)
• ISSN：1932-7455

文摘

Density functional theory calculations have been employed to investigate the effect of promoter Mn on ethanol formation from syngas on a Mn-promoted MnCu(211) surface. Our results show that CO + 3H 鈫?CHO + 2H 鈫?CH₂O + H 鈫?CH₃O is an optimal pathway for the overall CO conversion. Starting with CH₃O, CH₃ is formed via CH₃O 鈫?CH₃ + O. Then, CHO insertion into CH₃ can form CH₃CHO, and further, CH₃CHO is successively hydrogenated to ethanol via CH₃CH₂O intermediate. Meanwhile, CH₃OH is formed via CH₃O + H 鈫?CH₃OH. Compared to the pure Cu(211) surface, CH₃ formation is found to be energetically compatible with CH₃OH formation on the MnCu(211) surface, which can lead to more CH₃ sources and less CH₃OH; thus, the productivity and selectivity of ethanol can be improved. On the other hand, starting from CH₃, the MnCu(211) surface is more favorable for CHO insertion into CH₃ to CH₃CHO in comparison with CH₃ hydrogenation, dissociation and coupling to CH₄, CH₂, and C₂H₆ due to their high activation barriers; namely, the MnCu(211) surface exhibits a better selectivity toward C₂ oxygenates rather than hydrocarbons. As a result, we can show that, by introducing promoter Mn into Cu catalyst, the productivity and selectivity to ethanol from syngas can be effectively improved.