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    Synergistic effects of bimetallic Co-SnOx species in selective hydrogenation of methyl oleate: The crucial role of reduction characteristics
    (2026-09-01)
    Sooknoi, Tawan
    ;
    Thainoi, Suwimon
    ;
    Chanakha, Vichuda
    ;
    Ausavasukhi, Artit
    This study investigates the catalytic performance of bimetallic Co-Sn catalysts supported on alumina (Al<inf>2</inf>O<inf>3</inf>) for the selective hydrogenation of methyl oleate to oleyl alcohol. A strategic sequential reduction methodology, employing sodium borohydride followed by thermal hydrogen treatment (NaBH<inf>4</inf>-H<inf>2</inf>), was utilized to precisely tune the catalytic activity and chemoselectivity. Catalysts reduced solely with hydrogen at 300 °C exhibited limited efficiency, primarily favoring the formation of oleic acid via hydrogenolysis, which is attributed to the prevalence of cobalt oxide species. In contrast, the CoSnBH/Al<inf>2</inf>O<inf>3</inf> catalyst synthesized via a strategic sequential reduction methodology demonstrated a markedly enhanced selectivity toward oleyl alcohol, achieving a maximum selectivity of 54.1% at 270 °C and 8 MPa. Comprehensive characterization and kinetic analyses revealed that the superior performance stems from the synergistic coexistence of metallic cobalt (Co<sup>0</sup>) and low-valent tin oxides (SnO<inf>x</inf>), which form a bimetallic interface that preferentially polarizes the C=O bond. The catalytic efficiency was found to be highly sensitive to the nature of the support, the Co/Sn atomic ratio, and the total metal loading. Notably, turnover frequency (TOF) analysis indicated that while increased loading improves conversion, it may lead to site agglomeration and a reduction in surface-active concentration. Mechanistically, we propose that the CoSnBH/Al<inf>2</inf>O<inf>3</inf> system facilitates a direct hydrogenation pathway to oleyl alcohol, effectively bypassing the formation of heavy ester intermediates typically reported in literature.
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