Atomistic Engineering of Catalyst Precursors: Dynamic Reordering of PdAu Nanoparticles during Vinyl Acetate Synthesis Enhanced by Potassium Acetate

The presence of potassium acetate (KOAc) on bimetallic PdAu catalysts increases the rate of reaction for vinyl acetate (VA) formation from ethene and acetic acid by a factor of 10 and the selectivity by 20%. The dynamic transitions of typical supported catalyst precursors with an atomic Pd/Au ratio of 2/1 were explored during synthesis in the presence and absence of KOAc. The dopant induces reordering of PdAu toward a Pd1Au1 phase, while Au-enriched Pd40Au60 bimetallic particles form primarily in the absence of KOAc. Pd–acetate species are generated via leaching of Pd from PdAu precursor particles during the reaction. These species are Pd3(OAc)6 and Pd2(OAc)4 in the absence of KOAc and K2Pd2(OAc)6 in the presence of KOAc. Palladium in K2Pd2(OAc)6 can be readily reduced by C2H4 to Pd0, while Pd3(OAc)6, which contains more stable, bridged acetate ligands remains stable. Reduced Pd either forms dispersed Pd0 or is incorporated into the metal particles. KOAc enhances rates and selectivity to VA by stabilizing...