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Access type: UnknownSubject: search.filters.subject.Chemoselective hydrogenation

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    Tailoring the coordination environment of Co-Sn active sites via zinc aluminate spinel support for highly chemoselective hydrogenation of methyl oleate
    (2027-01-01)
    Sooknoi, Tawan
    ;
    Chanakha, Vichuda
    ;
    Wattanakul, Titiporn
    ;
    Ausavasukhi, Artit
    The chemoselective hydrogenation of methyl oleate to oleyl alcohol was investigated over Co-Sn catalysts supported on zinc aluminate (ZnAl<inf>2</inf>O<inf>4</inf>). The ZA-M support, synthesized via a methanol-mediated solvothermal route, provided a high specific surface area (296.8 m<sup>2</sup>/g) and an optimized mesoporous structure. Sequential NaBH<inf>4</inf> and H<inf>2</inf> reduction finely tuned the coordination of active sites, enabling the optimized 2Co4SnBH/ZA-M catalyst to achieve a superior oleyl alcohol yield (33.58%) and a high selectivity (65.39%) at a conversion level of 51.36% via a direct hydrogenation pathway. Based on bulk and surface characterizations, a fraction of cobalt was found to remain in a cationic state, stabilized within a network of interfacial Co-O-Sn complexes and framework CoAl<inf>2</inf>O<inf>4</inf>. These species are proposed to function as bifunctional active centers, where the Sn<sup>n+</sup>/Sn<sup>0</sup> species and neighboring Co<sup>2+</sup> sites cooperatively enhance the chemoselectivity toward C=O reduction. Furthermore, the optimized catalyst demonstrated reasonable structural stability and reusability over four cycles, maintaining its catalytic viability despite a minor extent of metal leaching. These findings underscore the efficacy of spinel-supported ionic-metallic ensembles for the highly chemoselective and efficient hydrogenation of long-chain fatty acid methyl esters.
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    Stabilized Pd Nanoparticles Encapsulated in MIL-101(Cr) for Chemoselective Hydrogenation of Polyunsaturated FAMEs
    (2025-11-24)
    Preedawichitkun, Yardthip
    ;
    Numwong, Natthida
    ;
    Chanlek, Narong
    ;
    Chung, Po Wen
    ;
    Kumar, Raju
    Palladium nanoparticles (Pd NPs) were successfully encapsulated within the porous framework of MIL-101(Cr) via a double solvent method to produce highly dispersed and stable catalysts for the chemoselective hydrogenation of polyunsaturated fatty acid methyl esters (FAMEs). Pd loadings ranging from 0.5 to 1.5 wt.% were systematically studied to elucidate the effects of nanoparticle size, dispersion, and hydrogen activation behavior on catalytic performance. The 0.8Pd/MIL-101(Cr) catalyst exhibited the highest turnover frequency (TOF ∼9,700 h<sup>−1</sup>) and superior selectivity (>90%) toward monounsaturated products (C18:1), attributed to optimal Pd dispersion. In contrast, the 0.5Pd/MIL-101(Cr) showed an induction period under low H<inf>2</inf> partial pressure, indicating limitations in hydride accommodation, while the 1.5Pd/MIL-101(Cr) suffered from Pd aggregation, resulting in a reduced intrinsic activity. Product selectivity was primarily governed by overall conversion: C18:1 was favored at low conversions, whereas C18:0 formation increased at higher conversions due to secondary hydrogenation. The catalysts demonstrated excellent stability and recyclability over multiple cycles without detectable Pd leaching or structural degradation. These findings establish MIL-101(Cr) as a robust and tunable platform for dispersing Pd NPs and highlight the potential of Pd/MIL-101(Cr) catalysts for efficient, selective upgrading of bioderived feedstocks under mild reaction conditions.
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