Browsing by Author "Sepulveda, Catherine"

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    STUDY OF THE CATALYTIC CONVERSION AND ADSORPTION OF ABIETIC ACID ON ACTIVATED CARBON: EFFECT OF SURFACE ACIDITY
    (2016) Garcia, Rafael; Peralta, Lorena; Segura, Cristina; Sepulveda, Catherine; Ghampson, I. Tyrone; Escalona, Nestor
    This study reports the adsorption and catalytic conversion of abietic acid as representative compound of tall oil, using activated carbons. Acid functional groups present on CGRAN activated carbons favored the adsorption of abietic acid, probably through a physical adsorption mechanism. In contrast, the conversion of abietic acid was not favored in DARCO activated carbon by increase of acid sites thought HNO3 treatment. The detection of neoabietic, palustric and/or levopimaric acids as reaction products indicate that the transformation of abietic acid was by dehydrogenation and/or isomerization routes. The negative influence of acid sites on the catalytic activity, in addition to the non-detection of volatile products, suggests that the cracking pathway for the conversion of abietic acid over these catalysts can be ruled out. Contrasting effects of the surface groups on the adsorption capacity and the conversion was observed: strong acid sites of CGRAN activated carbon favor the adsorption of abietic acid and decrease competitive adsorption between substrate and solvent, while conversion is not favored by these acid sites.
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    Thermal Modification Effect on Supported Cu-Based Activated Carbon Catalyst in Hydrogenolysis of Glycerol
    (2020) Seguel, Juan; Garcia, Rafael; Jose Chimentao, Ricardo; Luis Garcia-Fierro, Jose; Ghampson, I. Tyrone; Escalona, Nestor; Sepulveda, Catherine
    Glycerol hydrogenolysis to 1,2-propanediol (1,2-PDO) was performed over activated carbon supported copper-based catalysts. The catalysts were prepared by impregnation using a pristine carbon support and thermally-treated carbon supports (450, 600, 750, and 1000 degrees C). The final hydrogen adsorption capacity, porous structure, and total acidity of the catalysts were found to be important descriptors to understand catalytic performance. Oxygen surface groups on the support controlled copper dispersion by modifying acidic and adsorption properties. The amount of oxygen species of thermally modified carbon supports was also found to be a function of its specific surface area. Carbon supports with high specific surface areas contained large amount of oxygen surface species, inducing homogeneous distribution of Cu species on the carbon support during impregnation. The oxygen surface groups likely acted as anchorage centers, whereby the more stable oxygen surface groups after the reduction treatment produced an increase in the interaction of the copper species with the carbon support, and determined catalytic performances.