Theoretical studies of acrolein hydrogenation on silver catalysts

该项目将在微观层面上阐明银催化剂在a，b-不饱和醛的加氢反应中具有高选择性的原因，以生产具有重要技术意义的不饱和醇。为此，将对吸附在各种银衬底上的丙烯醛分子(作为代表性反应物)以及中间体、过渡态和加氢反应产物进行高水平密度泛函计算。将研究丙烯醛的C=O键和C=C键的氢化这两条相互竞争的反应途径所涉及的表面络合物。用单晶(111)、(100)和(110)银表面模拟可被“真正的”银催化剂暴露的规则面。表面不规则性将由阶梯状银表面的平板模型和银纳米团簇来表示。主要研究内容如下：1)丙烯醛及其加氢反应中间体和产物在银表面的吸附；2)原子氢在表面共吸附和/或溶解在次表面区域时的吸附体系；3)选择过渡态的位置来量化丙烯醛加氢反应的活化能垒。这一理论项目将补充P.Claus(TU Darmstadt)和R.Schlögl/A.Knop-Gericke(FHI柏林)小组在优先方案内的实验工作。

The project will seek to clarify at the microscopic level reasons for the high selectivity of silver catalysts in the hydrogenation of a,b-unsaturated aldehydes to produce technologically important unsaturated alcohols. For this purpose, high-level density functional calculations of acrolein molecules (as a representative reactant), adsorbed on various Ag substrates, as well as of intermediates, transition states, and products of the hydrogenation reactions will be carried out. Surface complexes involved in the two competing reaction pathways, hydrogenation of the C=O and C=C bonds of acrolein, will be studied. Regular facets that can be exposed by "real" silver catalysts will be modeled by single crystal (111), (100) and (110) Ag surfaces. Surface irregularities will be represented by slab models of stepped Ag surfaces as well as by Ag nanoclusters. The topics of the studies can be grouped as follows: 1) adsorption of acrolein, intermediates and products of its hydrogenation reactions on Ag substrates; 2) the same adsorption systems in the presence of atomic hydrogen co-adsorbed on the surface and/or dissolved in the subsurface region; 3) location of selected transition states to quantify activation energy barriers of acrolein hydrogenation. This theoretical project will supplement experimental efforts within the priority programme by the groups of P. Claus (TU Darmstadt) and R. Schlögl/A. Knop-Gericke (FHI Berlin).