Vajda Stefan, Lee Sungsik, Sell Kristian, Barke Ingo, Kleibert Armin, von Oeynhausen Viola, Meiwes-Broer Karl-Heinz, Rodríguez Arantxa Fraile, Elam Jeffrey W, Pellin Michael M, Lee Byeongdu, Seifert Sönke, Winans Randall E
Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA.
J Chem Phys. 2009 Sep 28;131(12):121104. doi: 10.1063/1.3237158.
The catalytic activity and dynamical shape changes in size-selected nanoclusters at work are studied under realistic reaction conditions by using a combination of simultaneous temperature-programmed reaction with in situ grazing-incidence small angle x-ray scattering. This approach allows drawing a direct correlation between nanocatalyst size, composition, shape, and its function under realistic reaction conditions for the first time. The approach is illustrated in a chemical industry highly relevant selective partial oxidation of propene on a monodisperse silver nanocatalyst. The shape of the catalyst undergoes rapid change already at room temperature upon the exposure to the reactants, followed by a complex evolution of shape with increasing temperature. Acrolein formation is observed around 50 degrees C while the formation of the propylene oxide exhibits a sharp onset at 80 degrees C and is leveling off at 150 degrees C. At lower temperatures acrolein is produced preferentially to propylene oxide; at temperatures above 100 degrees C propylene oxide is favored.
