Theoretical studies of acrolein hydrogenation on silver catalysts

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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).