Combined temperature-programmed reaction and in situ x-ray scattering studies of size-selected silver clusters under realistic reaction conditions in the epoxidation of propene.
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.
Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA. vajda@anl.gov
Stefan
S
Vajda
Sungsik
S
Lee
Kristian
K
Sell
Ingo
I
Barke
Armin
A
Kleibert
Viola
V
von Oeynhausen
Karl-Heinz
KH
Meiwes-Broer
Arantxa Fraile
AF
Rodríguez
Jeffrey W
JW
Elam
Michael M
MM
Pellin
Byeongdu
B
Lee
Sönke
S
Seifert
Randall E
RE
Winans