Tracking Rh Atoms in Zeolite HY: First Steps of Metal Cluster Formation and Influence of Metal Nuclearity on Catalysis of Ethylene Hydrogenation and Ethylene Dimerization.
The initial steps of rhodium cluster formation from zeolite-supported mononuclear Rh(C2H4)2 complexes in H2 at 373 K and 1 bar were investigated by infrared and extended X-ray absorption fine structure spectroscopies and scanning transmission electron microscopy (STEM). The data show that ethylene ligands on the rhodium react with H2 to give supported rhodium hydrides and trigger the formation of rhodium clusters. STEM provided the first images of the smallest rhodium clusters (Rh2) and their further conversion into larger clusters. The samples were investigated in a plug-flow reactor as catalysts for the conversion of ethylene + H2 in a molar ratio of 4:1 at 1 bar and 298 K, with the results showing how the changes in catalyst structure affect the activity and selectivity; the rhodium clusters are more active for hydrogenation of ethylene than the single-site complexes, which are more selective for dimerization of ethylene to give butenes.
Department of Chemical Engineering, University of California , Davis, California 95616, United States.
Dong
D
Yang
Department of Chemical Engineering, University of California , Davis, California 95616, United States.
Pinghong
P
Xu
Physical and Computational Sciences, Pacific Northwest National Laboratory , 902 Battelle Boulevard, Richland, Washington 99352, United States.
Nigel D
ND
Browning
Department of Chemical Engineering, University of California , Davis, California 95616, United States.
Bruce C
BC
Gates