| 1. |
- Hu, Tianhao, et al.
(författare)
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Interaction of Anisole on Alumina-Supported Ni and Mo Oxide Hydrodeoxygenation Catalysts
- 2023
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Ingår i: Journal of Physical Chemistry C. - 1932-7447. ; 127:39, s. 19440-19450
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Tidskriftsartikel (refereegranskat)abstract
- The conversion of biomass to transportation fuels and value-added chemicals is a promising method to reduce the reliance on fossil fuels. Mo-based catalysts have been shown to be highly active in the hydrodeoxygenation of biomass-derived phenolic compounds. The catalyst active phase, surface species, and the effect of adding additional metals are not comprehensively understood. Here we compare the temperature-dependent adsorption behavior of the model compound anisole on an alumina-supported mixed nickel molybdenum oxide catalyst with two reference catalysts, molybdenum oxide and nickel oxide. Raman spectroscopy showed that the catalysts contain significant amounts of molybdates and molybdoaluminates, in addition to NiMoO4 in the nickel molybdenum catalyst and MoO3 in the molybdenum-only catalyst. Using transmission infrared spectroscopy under a controlled environment, we find that anisole chemisorbed largely through the oxygen in the methoxy group to form surface-bound phenoxy and methoxy species on all of the catalysts. Ambient pressure X-ray photoelectron spectroscopy measurements of the catalysts in anisole vapor showed reduced Mo atoms are the binding sites. The surface interaction and removal temperature of these species varied with the metal composition. The MoOx component dominated the adsorption behavior in both MoOx and NiMoOx catalysts. The formation of new aromatics, including methylated rings, depended on the Ni composition. Upon the addition of hydrogen to induce the hydrodeoxygenation of anisole, undesirable polynuclear aromatic species were quickly formed on the Mo-based catalysts. These results suggest that the molybdenum oxide controls the adsorption and reactivity of the surface species with a cooperative effect by Ni.
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| 2. |
- Wang, Chunlei, et al.
(författare)
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Stabilization of Cu2O through Site-Selective Formation of a Co1Cu Hybrid Single-Atom Catalyst
- 2022
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 34:5, s. 2313-2320
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Tidskriftsartikel (refereegranskat)abstract
- Single-atom catalysts (SACs) consist of a low coverage of isolated metal atoms dispersed on a metal substrate, called single-atom alloys (SAAs), or alternatively single metal atoms coordinated to oxygen atoms on an oxide support. We present the synthesis of a new type of Co1Cu SAC centers on a Cu2O(111) support by means of a site-selective atomic layer deposition technique. Isolated metallic Co atoms selectively coordinate to the native oxygen vacancy sites (Cu sites) of the reconstructed Cu2O(111) surface, forming a Co1Cu SAA with no direct Co- Ox bonds. The centers, here referred to as Co1Cu hybrid SACs, are found to stabilize the active Cu+ sites of the low-cost Cu2O catalyst that otherwise is prone to deactivation under reaction conditions. The stability of the Cu2O(111) surface was investigated by synchrotron radiation-based ambient-pressure X-ray photoelectron spectroscopy under reducing CO environment. The structure and reduction reaction are modeled by density functional theory calculations, in good agreement with experimental results.
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