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Theoretical understanding on the selectivity of acrolein hydrogenation over silver surfaces: the non-Horiuti–Polanyi mechanism is the key
Catalysis Science & Technology ( IF 5 ) Pub Date : 2017-08-11 00:00:00 , DOI: 10.1039/c7cy01500c
Kaili Wang 1, 2, 3, 4, 5 , Bo Yang 1, 2, 3, 4
Affiliation  

Chemoselective hydrogenation of α,β-unsaturated aldehydes to unsaturated alcohols is not only an important reaction in the chemical industry but also a good model system to understand the catalytic selectivity in heterogeneous catalysis. In the current work, the selectivity of partial hydrogenation of acrolein (C3H4O), the simplest α,β-unsaturated aldehyde, is investigated employing density functional theory (DFT) calculations. Two hydrogenation mechanisms, namely the Horiuti–Polanyi mechanism and the non-Horiuti–Polanyi mechanism, are employed to study the partial hydrogenation of acrolein over Ag(111), Ag(100), Ag(211) and Ag(111)-mono surfaces. It is found that the hydrogenation of C3H4O to C3H5O at the terminal carbon and oxygen atoms follows the non-Horiuti–Polanyi mechanism in which C3H4O reacts with hydrogen molecules directly over all the silver surfaces studied, whilst atomic hydrogen is the active hydrogen species for the hydrogenation of C3H5O to C3H6O. Subsequently, the selectivities between partial hydrogenation products, i.e. propenol, propanal and enol, over silver surfaces with different morphologies are compared by calculating the energy difference between the rate-determining transition states. We find that the selectivity of propenol formation increases with the coordination number of surface silver atoms, which is in good agreement with the trend of selectivities obtained experimentally. It is also interesting to find that the selectivity trend obtained based solely upon the Horiuti–Polanyi mechanism for the hydrogenation of C3H4O to C3H5O and C3H5O to C3H6O cannot explain the experimental results. In other words, the non-Horiuti–Polanyi mechanism is able to give a more reasonable explanation for the selectivity trend observed experimentally than the normally used Horiuti–Polanyi mechanism in heterogeneous catalysis. Our work highlights the significance of the non-Horiuti–Polanyi mechanism in understanding heterogeneous catalytic hydrogenation reactions.

中文翻译:

对银表面上丙烯醛加氢选择性的理论理解:非Horiuti-Polanyi机理是关键

α,β-不饱和醛化学选择性加氢为不饱和醇不仅是化学工业中的重要反应,而且是理解多相催化中催化剂选择性的良好模型体系。在当前的工作中,使用密度泛函理论(DFT)计算研究了最简单的α,β-不饱和醛丙烯醛(C 3 H 4 O)的部分氢化的选择性。利用两种氢化机理,即Horiuti-Polanyi机理和非Horioti-Polanyi机理,研究了丙烯醛在Ag(111),Ag(100),Ag(211)和Ag(111)-mono上的部分氢化。表面。发现将C 3 H 4 O氢化为C 3 H末端碳原子和氧原子上的5 O遵循非Horiuti-Polanyi机理,其中C 3 H 4 O与氢分子直接在所有研究的银表面上反应,而原子氢是C 3氢化的活性氢ħ 5 ø至C 3 ħ 6 O.随后,部分氢化的产品之间的选择性,通过计算决定速率的过渡态之间的能量差,比较具有不同形态的银表面上的丙二醇,丙醛和烯醇。我们发现,丙烯醇形成的选择性随表面银原子配位数的增加而增加,这与通过实验获得的选择性趋势很好地吻合。这也是有趣地发现,选择性趋势得到的仅基于所述Horiuti-波拉尼机构C的氢化3 ħ 4 ø至C 3 ħ 5 O,C的3 ħ 5 ø至C 3 ħ 6O无法解释实验结果。换句话说,在非均相催化中,非Horiuti-Polanyi机理能够比通常使用的Horiuti-Polanyi机理更合理地解释实验观察到的选择性趋势。我们的工作突出了非Horiuti-Polanyi机理在理解非均相催化加氢反应中的重要性。
更新日期:2017-09-18
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