Browsing by Author "Poon, Po S."

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    Alkali-Boosted Catalytic Activity of Co-Based Catalysts Supported by Nanoporous Carbon in the Hydrodeoxygenation of Guaiacol
    (2025) Matos, Juan; Samudio González, Diana; Blanco, Elodie; Poon, Po S.; Escalona Burgos, Néstor Guillermo
    The catalytic activity and selectivity of Co-based catalysts supported on home-made nanoporous carbon was studied as a function of the type of alkali promoter (Ca and Mg). The catalysts were characterized by N2 adsorption/desorption isotherms, temperature-programmed reduction, CO chemisorption, and X-ray diffraction patterns. The catalysts were compared against carbon-supported alkali-promoted Ni-based catalysts and Re-containing catalysts. The catalytic activity of the Co-based catalyst was clearly enhanced in the presence of Ca and Mg, and it was higher than the Ni-based catalysts and comparable to that obtained using an ReC catalyst. The initial activity of the Mg-promoted catalyst increased by a factor of up to 2.5 times higher compared to the non-promoted catalyst. Moreover, this catalyst showed a turnover frequency of up to 5 times higher than equivalent carbon-supported Re-based catalysts. Significant changes were not observed in the selectivity of products after the incorporation of alkali, with cyclohexane being the main product. However, it was demonstrated that the presence of alkali led to a faster and higher production of cyclohexane from the demethoxylation of phenol and the dehydrogenation of cyclohexanol. The present results suggest that Co-based catalysts are an economical alternative for the catalytic conversion of representative target molecules from bio-oil feed.
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    Alkali-driven selectivity of products on carbon-supported Ni-based catalysts during the HDO of guaiacol
    (2024) Matos, Juan; Samudio-González, Diana; Blanco, Elodie; Poon, Po S.; Escalona Burgos, Néstor Guillermo
    The catalytic hydrodeoxygenation (HDO) of guaiacol as a representative bio-oil molecule was studied using a series of carbon-supported Ni-based catalysts. The promoter effect of alkali metals (Ca and Mg) on the catalytic activity and selectivity was verified. Catalysts were prepared by wetness incipient method and N2 gas adsorp tion/desorption isotherms, X-ray diffraction, reduction/desorption temperature-programed, and CO chemi sorption analysis were performed to characterize the catalysts. In terms of the initial reaction-rate catalysts with 1 wt% alkali-promotors showed an increase in the activity up to ca. 1.4 and 1.2 times higher on Ni-Ca(1 %)/AC and Ni-Mg(1 %)/AC, respectively, compared to Ni/AC catalyst. The increase to 5 wt% in alkali promotors slightly reduced the initial activity of Ni. However, the turn-over frequencies estimated showed higher values when alkali content is increased from 1 wt% to 5 wt%. These apparent contradictorial results suggest the formation of new actives sites along reaction, probably constituted by a mixture of oxides NiO-CaO and NiO-MgO. The selectivity of products showed remarkable changes due to the presence of alkali-promotors and a mechanism or reaction is proposed based on the kinetics of formation and evolution of products. Mg-promoted led to the formation of cyclohexane. On the contrary, Ca-promoted catalysts led the mechanism to representative benzene yields. This is remarkable result regarding the efficiency of a HDO biorefinery. In general, it can be concluded that Ni-based catalysts promoted with alkali metals are an economical alternative for the catalytic conversion of representa tive target molecules from a bio-oil feed.