Impregnation of KOAc on PdAu/SiO2 causes Pd-acetate formation and metal restructuring

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dc.citation.firstpage6918en_US
dc.citation.journalTitleJournal of Materials Chemistry Aen_US
dc.citation.lastpage6933en_US
dc.citation.volumeNumber11en_US
dc.contributor.authorJacobs, Hunter P.en_US
dc.contributor.authorElias, Welman C.en_US
dc.contributor.authorHeck, Kimberly N.en_US
dc.contributor.authorDean, David P.en_US
dc.contributor.authorDodson, Justin J.en_US
dc.contributor.authorZhang, Wenqingen_US
dc.contributor.authorArredondo, Jacob H.en_US
dc.contributor.authorBreckner, Christian J.en_US
dc.contributor.authorHong, Kiheonen_US
dc.contributor.authorBotello, Christopher R.en_US
dc.contributor.authorChen, Laiyuanen_US
dc.contributor.authorMueller, Sean G.en_US
dc.contributor.authorAlexander, Steven R.en_US
dc.contributor.authorMiller, Jeffrey T.en_US
dc.contributor.authorWong, Michael S.en_US
dc.date.accessioned2023-05-02T18:37:01Zen_US
dc.date.available2023-05-02T18:37:01Zen_US
dc.date.issued2023en_US
dc.description.abstractPotassium-promoted, oxide-supported PdAu is catalytically active for the gas-phase acetoxylation of ethylene to form vinyl acetate monomer (VAM), in which the potassium improves long-term activity and VAM selectivity. The alkali metal is incorporated into the catalyst via wet impregnation of its salt solution, and it is generally assumed that this common catalyst preparation step has no effect on the catalyst structure. However, in this work, we report evidence to the contrary. We synthesized a silica-supported PdAu (PdAu/SiO2, 8 wt% Pd, 4 wt% Au) model catalyst containing Pd-rich PdAu alloy and pure Au phases. Impregnation with potassium acetate (KOAc) aqueous solution and subsequent drying did not cause XRD-detectible changes to the bimetal structure. However, DRIFTS indicated the presence of Pd3(OAc)6 species, which is correlated to up to 2% Pd loss after washing of the dried KOAc-promoted PdAu/SiO2. Carrying out the impregnation step with an AcOH-only solution and subsequent drying caused significant enlargement of the pure Au grain size and generated a smaller amount of Pd3(OAc)6. During co-impregnation of AcOH and KOAc, grain sizes were enlarged slightly, and substantial amounts of K2Pd2(OAc)6 and Pd3(OAc)6 were detected by DRIFTS and correlated to up to 32% Pd loss after washing. Synchrotron XAS analysis showed that approximately half the Pd atoms were oxidized, corroborating the presence of the Pd-acetate species. These results indicate wet-impregnation-induced metal leaching can occur and be substantial during catalyst preparation.en_US
dc.identifier.citationJacobs, Hunter P., Elias, Welman C., Heck, Kimberly N., et al.. "Impregnation of KOAc on PdAu/SiO2 causes Pd-acetate formation and metal restructuring." <i>Journal of Materials Chemistry A,</i> 11, (2023) Royal Society of Chemistry: 6918-6933. https://doi.org/10.1039/D3TA00820G.en_US
dc.identifier.doihttps://doi.org/10.1039/D3TA00820Gen_US
dc.identifier.urihttps://hdl.handle.net/1911/114872en_US
dc.language.isoengen_US
dc.publisherRoyal Society of Chemistryen_US
dc.rightsThis is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by The Royal Society of Chemistry.en_US
dc.titleImpregnation of KOAc on PdAu/SiO2 causes Pd-acetate formation and metal restructuringen_US
dc.typeJournal articleen_US
dc.type.dcmiTexten_US
dc.type.publicationpost-printen_US
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