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

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dc.citation.firstpage6918
dc.citation.journalTitleJournal of Materials Chemistry A
dc.citation.lastpage6933
dc.citation.volumeNumber11
dc.contributor.authorJacobs, Hunter P.
dc.contributor.authorElias, Welman C.
dc.contributor.authorHeck, Kimberly N.
dc.contributor.authorDean, David P.
dc.contributor.authorDodson, Justin J.
dc.contributor.authorZhang, Wenqing
dc.contributor.authorArredondo, Jacob H.
dc.contributor.authorBreckner, Christian J.
dc.contributor.authorHong, Kiheon
dc.contributor.authorBotello, Christopher R.
dc.contributor.authorChen, Laiyuan
dc.contributor.authorMueller, Sean G.
dc.contributor.authorAlexander, Steven R.
dc.contributor.authorMiller, Jeffrey T.
dc.contributor.authorWong, Michael S.
dc.date.accessioned2023-05-02T18:37:01Z
dc.date.available2023-05-02T18:37:01Z
dc.date.issued2023
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.
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.
dc.identifier.doihttps://doi.org/10.1039/D3TA00820G
dc.identifier.urihttps://hdl.handle.net/1911/114872
dc.language.isoeng
dc.publisherRoyal Society of Chemistry
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.
dc.titleImpregnation of KOAc on PdAu/SiO2 causes Pd-acetate formation and metal restructuring
dc.typeJournal article
dc.type.dcmiText
dc.type.publicationpost-print
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