Examinando por Autor "Conesa, J.M."

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  • Miniatura
    Publicación
    Carbon-supported non-noble metal catalysts for efficient synthesis of the biofuel 2,5-dimethylfurfural from 5‑hydroxymethylfurfural in 1-butanol under mild conditions
    (ELSEVIER, 2025-04-01) Morales Vargas, Mª Virtudes; Conesa, J.M.; Guerrero Ruiz, A.; Rodríguez Ramos, I.
    2,5-Dimethylfuran (DMF), which is one of the most promising liquid biofuels, has garnered significant attention due to its potential to develop the utilization of biomass energy. In this work, its synthesis through the hydrodeoxygenation reaction (HDO) of 5-hydroxymethylfurfural (HMF) has been studied on Ni catalysts supported on various metal oxides and a high surface graphite (HSAG), in a batch reactor, using 1-butanol as a solvent. At 180 °C and under 30 bar H2, the catalytic activity and the predominant reaction route were found to be strongly conditioned by the nature of the support, as well as by the presence of impurities depending on the commercial HMF feedstock employed. The HSAG support turned out to be the most suitable for the HDO of HMF leading to the formation of DMF, via rupture of the C-O bonds. Additionally, the catalytic performance of Co and Cu supported on this graphitic material was studied, being Cu the one that offers the best yields to DMF (95 %), even in the absence of external hydrogen (84 %), confirming that butanol acts as a hydrogen donor in addition of solvent.
  • Miniatura
    Publicación
    Comparative study of Cu, Ag and Ag-Cu catalysts over graphite in the ethanol dehydrogenation reaction: Catalytic activity, deactivation and regeneration
    (ELSEVIER, 2019) Conesa, J.M.; Morales, María V.; López-Olmos, Cristina; Rodríguez Ramos, Inmaculada; Guerrero Ruiz, Antonio R; https://orcid.org/0000-0003-2834-0296; https://orcid.org/0000-0003-4622-6008; https://orcid.org/0000-0003-1848-5985
    The physicochemical and catalytic properties of bimetallic AgCu catalysts and their monometallic counterparts supported on a high surface area graphite have been comparatively evaluated in the ethanol dehydrogenation reaction, performed in a continuous-flow reactor. While Cu was incorporated by the incipient wetness impregnation technique, for Ag catalysts two synthesis procedures were explored: incipient wetness impregnation and adsorption of Tollens’ reagent. The catalysts prepared by wetness impregnation exhibited higher metal dispersion, being improved for the bimetallic catalysts in comparison with the monometallic counterparts. The results obtained in the catalytic tests revealed that Cu catalysts is nearly two orders of magnitude more active than Ag catalyst in the dehydrogenation reaction of ethanol on either a turnover frequency or a weight basis, but at the same time both catalysts were 100% selective to acetaldehyde. Whereas selectivity was not affected by the bimetallic composition, there was a substantial decrease in the reaction rate among the bimetallic catalysts as the Cu/Ag ratio diminished, due to blockage of copper surface active sites by silver. Both silver and copper, and the bimetallic catalysts, suffered from deactivation at 523 K, caused by blocking of active sites by adsorbed hydrocarbons on the catalyst surface (fouling). Carbonaceous deposits were removed through a thermal treatment under H2 flow, which allowed the total recovery of the initial catalytic activity.