Dynamic Phase Separation in Supported Pd-Au Catalysts

作者：Simson Stefanie; Jentys Andreas; Lercher Johannes A^*

来源：Journal of Physical Chemistry C, 2015, 119(5): 2471-2482.

DOI：10.1021/jp510089s

SiO2-supported Pd-Au catalysts with Pd/Au molar ratios varying from 0.8 to 7.0 were used as catalysts for vinyl acetate synthesis under industrial conditions. Continued operation of the bimetallic catalysts at 150 degrees C led to the formation of the Pd1Au1 phase in the particles, with the remaining Pd atoms forming Pd nanoparticles by leaching of Pd as acetate. The presence of these phases was monitored by X-ray absorption spectroscopy (XAS) of the used catalysts. Temperature-resolved in situ XRD of the reduced samples in an inert atmosphere confirmed the phase separation into a Pd-rich phase and a Au-rich phase above 160 degrees C. CO adsorption and XRD of the catalysts used at 180 degrees C showed that phase separation also took place during vinyl acetate synthesis. The pronounced temperature dependence of the morphology and surface composition of the bimetallic Pd-Au catalysts determines the selectivity; the activity; and, in particular, the stability during vinyl acetate synthesis.

• 出版日期2015-2-5