Browsing by Author "Arredondo, Jacob H."

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    Heavy oil viscosity reduction at mild temperatures using palladium acetylacetonate
    (Elsevier, 2021) Xu, Yan; Heck, Kimberly N.; Ayala-Orozco, Ciceron; Arredondo, Jacob H.; Zenor, William; Shammai, Michael; Wong, Michael S.
    Metal-ligand compounds (“MLCs”) have been shown to reduce heavy oil viscosity and upgrade oil quality. However, MLCs generally require high treatment temperatures (around 250 °C), which is undesirably energy-intensive. We identified palladium(II) acetylacetonate (“PdA”) as a model MLC that can operate at mild temperatures (<200 °C). We studied its effectiveness on heavy oil viscosity reduction in the range of 80–300 °C using viscometry, SARA analysis, GC–MS, XPS, and XRD to characterize Peace River oil samples thermally treated with and without PdA. This MLC effectively lowered oil viscosity at all treatment temperatures, whereas thermal-only treatments did not reduce viscosity below 160 °C. The thermal treatment with PdA in the 130–250 °C range reduced viscosity by up to ~35% more than the thermal treatment alone. GC–MS and TGA results indicated the PdA partially decomposed at 80 °C and higher temperatures, releasing acetylacetone (“HA”), which lowered oil viscosity. The temperature and HA effects did not completely account for the observed viscosity reduction from thermal treatment with PdA, indicating there were other significant effects. In the 80–130 °C range, the asphaltene fraction increased due to PdA or its decomposition products intercalating into the asphaltene clusters. At temperatures around 250 °C, the resin fraction decreased, correlating to in situ formed metallic Pd that catalytically hydrogenate the resin sulfonyl groups to aliphatic sulfur. This new understanding of the temperature-dependent impact – acetylacetonate ligand, MLC-asphaltene attraction, and palladium metal catalyst formation – on oil viscosity changes provides an improved approach to developing new MLCs for field-relevant conditions.
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    Impregnation of KOAc on PdAu/SiO2 causes Pd-acetate formation and metal restructuring
    (Royal Society of Chemistry, 2023) Jacobs, Hunter P.; Elias, Welman C.; Heck, Kimberly N.; Dean, David P.; Dodson, Justin J.; Zhang, Wenqing; Arredondo, Jacob H.; Breckner, Christian J.; Hong, Kiheon; Botello, Christopher R.; Chen, Laiyuan; Mueller, Sean G.; Alexander, Steven R.; Miller, Jeffrey T.; Wong, Michael S.
    Potassium-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.