Examinando por Autor "Serrano, David Pedro"

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Selective hydrocarboxylation of fatty acids into long-chain hydrocarbons catalyzed by Pd/Al-SBA-15
(Elsevier, 2019-01-29) Serrano, David Pedro; Escola, José María; Briones, Laura; Arroyo, Marta
Pd/Al-SBA-15 materials, with different Si/Al atomic ratios, have been investigated as catalysts in the hydrodecarboxylation (HDC) of fatty acids for the production of long-chain paraffinic hydrocarbons. The catalytic tests were performed in a stirred batch reactor under H2 atmosphere using stearic, oleic and palmitic acids as substrates. Characterization of the catalysts indicates that the Pd nanoparticles are well distributed on the support, being partially located within their ordered mesopores. Increasing the Al-SBA-15 acidity enhances the stearic acid conversion but provokes a reduction in the selectivity towards hydrodecarboxylation versus hydrodeoxygenation (HDO). Variation of the reaction temperature within 225 - 300 ºC enhanced the catalytic activity, while the HDC selectivity remained over 90%, being just reduced when working at 300 ºC due to the occurrence of cracking reactions. The H2 pressure also increased the stearic acid conversion, in particular when passing from 3 to 6 bar, confirming the positive role of the hydrogen atmosphere in the decarboxylation process. However, when operating at 25 bar of H2 pressure, the HDC selectivity decreases, as the HDO pathway is favored. Comparing the results obtained with stearic, oleic and palmitic acids shows that the Pd/Al-SBA-15 system is an excellent catalyst for this reaction, providing in all cases a significant catalytic activity and a very high HDC selectivity. These findings can be related to the features of the Al-SBA-15 support (high surface area, uniform mesopores and mild Lewis acidity), which provides a good Pd dispersion, a high substrate accessibility and limit the extension of cracking reactions.
Shifting pathways in the phenol/2-propanol conversion over the tandem Raney Ni + ZSM-5 catalytic system
(American Chemical Society, 2020-02-04) García-Minguillán, Alba María; Briones, Laura; Serrano, David Pedro; Botas, Juan Ángel; Escola, José María
This work investigates the effects of both the zeolite accessibility and the reaction temperature on conversion of phenol assisted by 2-propanol over the tandem system Raney Ni + ZSM-5 zeolite. Two different zeolite samples, containing similar Si/Al ratios, were used: nanocrystalline ZSM-5 (n-ZSM-5) and hierarchical ZSM-5 (h-ZSM-5), operating at temperatures of 125, 150 and 175°C. When working with the Raney Ni + n-ZSM-5 system at low and intermediate temperatures the main products were mostly benzene and cyclohexene formed by phenol deoxygenation. In contrast, when increasing the temperature up to 175°C, a shift in the reaction pathways was observed, leading towards a significant share of valuable alkylphenols (mostly cresols and cyclohexylphenols) in the product distribution, generated by the occurrence of alkylation reactions catalyzed by the zeolite acid sites. This effect was enhanced in the case of the h-ZSM-5 sample, due to its improved accessibility and larger mesopore/external surface area.