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    Tuning Cu+ species/Brønsted acids of copper phyllosilicate by K+ doping for selective hydrogenation of methyl palmitate to hexadecanol
    (2023-12-01)
    Prasanseang, Warot
    ;
    Choojun, Kittisak
    ;
    Poo-arporn, Yingyot
    ;
    Huang, Ai Lin
    ;
    Lin, Yu Chuan
    Selective hydrogenation of methyl palmitate to hexadecanol can be manipulated by tuning Cu<sup>+</sup> species and Brønsted acid sites (BAS) of copper phyllosilicate (CuPS) catalysts with K<sup>+</sup> doping. The catalysts were prepared by impregnating K<sup>+</sup> onto reduced and non-reduced CuPS. The reactions were carried out in a fixed-bed flow reactor at 250 °C under atmospheric H<inf>2</inf>. In situ TR-XANES and Py-IR suggest that the presence of K<sup>+</sup> could stabilize Cu<sup>+</sup> species and neutralize BAS. As compared to the non-reduced sample, K<sup>+</sup> loading (0.01–0.10 wt%) on the reduced CuPS provide higher Cu<sup>+</sup> fraction (10–16%), lower BAS (0.82 to 0.16μ mol/g) and lower Cu dispersion (75 to 52%). A balance between Cu<sup>0</sup> active surface and Cu<sup>+</sup> content provides an optimum hydrogenation activity (up to 80 %). The increased Cu<sup>+</sup> species, together with the decreased BAS, does not only enhance the catalyst stability, but also hexadecanol selectivity (from 35 to 60%, at ∼50% conversion).
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    Facile synthesis of the atomically dispersed hydrotalcite oxide supported copper catalysts for the selective hydrogenation of 5–hydroxymethylfurfural into 2,5-bis(hydroxymethyl)furan
    (2023-07-15)
    Kumar, Raju
    ;
    Lee, Hsin Hui
    ;
    Chen, En
    ;
    Du, Yuan Peng
    ;
    Lin, Chan Yi
    The selective hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-bis(hydroxymethyl)furan (BHMF) using the atomically dispersed supported copper catalyst is investigated. The hydrotalcite oxide supported copper materials (Cu<inf>(x)</inf>HTO) are facilely prepared by coprecipitating metal precursors in a methanolic solution under a tuned pH. The surface characterization involving PXRD, TEM, H<inf>2</inf>/N<inf>2</inf>O-TPR, and XAS reveals unequivocal evidence for the presence of the atomically dispersed copper on HTO surface. XAS specifically indicates the formation of mononuclear copper species, and H<inf>2</inf>/N<inf>2</inf>O-TPR strongly supports the copper atoms of Cu<inf>(5)</inf>HTO are evenly distributed in 99% dispersion. Moreover, the reduced Cu<inf>(5)</inf>HTO (r-Cu<inf>(5)</inf>HTO) enables to completely hydrogenate HMF to BHMF under mild conditions, in comparison to the poor reactivity catalyzed by the hydrotalcite oxide supported copper nanoparticles (r-Cu<inf>(4)</inf>@HTO). The dramatic enhancement of HMF hydrogenation catalyzed by r-Cu<inf>(5)</inf>HTO can be attributed to the fine distribution of copper atoms which are situated homogeneously over HTO surface as well as chemically reactive for the carbonyl group.