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118 results on '"Fierro, Jose L. G."'

4. Silica Bifunctional Supports for the Direct Synthesis of H 2 O 2 : Optimization of Br/Acid Sites and Pd/Br Ratio.

Author

Blanco-Brieva, Gema, Desmedt, Frederique, Miquel, Pierre, Campos-Martin, Jose M., and Fierro, Jose L. G.

Subjects
SILICA, SULFONIC acids, HYDROGEN production, CATALYST testing, CATALYST synthesis, HYDROGEN peroxide, PALLADIUM
Abstract

We have studied the direct synthesis of hydrogen peroxide using a catalytic system consisting of palladium supported on silica bifunctionalized with sulfonic acid groups and bromide in the absence of acid and halide promoters in solution. Catalysts with several bromide substituents were employed in the catalyst synthesis. The prepared samples were characterized by TXRF, XPS, and hydrogen peroxide decomposition. Catalysts characterization indicated the presence of only palladium (II) species in all of the samples, with similar values for surface and bulk of Pd/Br atomic ratio. The catalysts were tested via direct synthesis, and all samples were able to produce hydrogen peroxide at 313 K and 5.0 MPa. The hydrogen peroxide yield and selectivity changed with the Pd/Br ratio. A decrease in the Pd/Br ratio increases the final hydrogen peroxide concentration, and the selectivity for H2O2 reaches a maximum at a Pd/Br ratio around 0.16 and then decreases. However, the maximum hydrogen peroxide concentration and selectivity occur at slightly different Pd/Br ratios, i.e., resp. 0.4 vs. 0.16. [ABSTRACT FROM AUTHOR]

Published
2022
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13. Enantioselective desymmetrization of prochiral diesters catalyzed by immobilized Rhizopus oryzae lipase

Author

Campos, Cristian H., Torres, Cecilia, Fierro, Jose L. G., and Reyes, Patricio

Subjects
chemistry.chemical_classification, biology, Organic Chemistry, Enantioselective synthesis, Rhizopus oryzae, biology.organism_classification, Aldehyde, Desymmetrization, Catalysis, Inorganic Chemistry, Solvent, Hydrolysis, chemistry, biology.protein, Organic chemistry, Physical and Theoretical Chemistry, Lipase, Selectivity
Abstract

The asymmetric hydrolysis of dimethyl 3-phenylglutarate 1 catalyzed by different immobilized preparations of Rhizopus oryzae lipase (ROL) has been studied. The Lewatit CNP 105 commercial support was activated to aldehyde groups (Lewatit-aldehyde) and used as a support for the immobilization of ROL using different strategies. Thus, the lipase immobilized in the presence of dithiothreitol at pH 7 (ROL-Lew-pH 7) was the most enantioselective catalyst for the hydrolysis of 1 at pH 7 and 25 °C producing the ( R )-monoester with an E value of 4.2 (ee = 62%) whereas ROL immobilized at pH 10 gave only an E value of 1.1 (ee = 4%). The medium engineering was also an interesting tool for improving the lipase selectivity. The addition of a solvent, combined with decreasing temperature improved the E value for the reaction from 4.2 to 24 (ee = 62 to ee = 92%). Finally, the application of the ROL-Lew-pH 7 preparation in the presence of 20% dioxane and 5 °C allowed us to obtain the ( R )-isomer of the monoester with an E value of 24 (ee = 92%) in a 97% yield (of monoesters).

Published
2011
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14. Bioinspired Electro-Organocatalytic Material Efficient for Hydrogen Production

Author

Moral, Octavio González-del, primary, Call, Arnau, additional, Franco, Federico, additional, Moya, Alicia, additional, Nieto-Rodríguez, Jose Antonio, additional, Frias, María, additional, Fierro, Jose L. G., additional, Costas, Miquel, additional, Lloret-Fillol, Julio, additional, Alemán, José, additional, and Mas-Ballesté, Rubén, additional

Published
2018
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17. Triazine-Carbon Nanotubes: New Platforms for the Design of Flavin Receptors

Author

Lucío, María Isabel, primary, Pichler, Federica, additional, Ramírez, José Ramón, additional, de la Hoz, Antonio, additional, Sánchez-Migallón, Ana, additional, Hadad, Caroline, additional, Quintana, Mildred, additional, Giulani, Angela, additional, Bracamonte, Maria Victoria, additional, Fierro, Jose L. G., additional, Tavagnacco, Claudio, additional, Herrero, María Antonia, additional, Prato, Maurizio, additional, and Vázquez, Ester, additional

Published
2016
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18. Bioinspired Electro‐Organocatalytic Material Efficient for Hydrogen Production.

Author

Moya, Alicia, Nieto‐Rodríguez, Jose Antonio, Moral, Octavio González‐del, Mas‐Ballesté, Rubén, Call, Arnau, Costas, Miquel, Franco, Federico, Lloret‐Fillol, Julio, Frias, María, Alemán, José, and Fierro, Jose L. G.

Subjects
HYDROGEN production, BENZYL alcohol, GRAPHENE, BENZALDEHYDE, DENSITY functional theory
Abstract

Abstract: Commercial carbon fibers can be used as electrodes with high conductive surfaces in reduced devices. Oxidative treatment of such electrodes results in a chemically robust material with high catalytic activity for electrochemical proton reduction, enabling the measurement of quantitative faradaic yields (>95 %) and high current densities. Combination of experiments and DFT calculations reveals that the presence of carboxylic groups triggers such electrocatalytic activity in a bioinspired manner. Analogously to the known Hantzsch esters, the oxidized carbon fiber material is able to transfer hydrides, which can react with protons, generating H2, or with organic substrates resulting in their hydrogenation. A plausible mechanism is proposed based on DFT calculations on model systems. [ABSTRACT FROM AUTHOR]

Published
2018
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23. Exploring the Structural and Electronic Properties of Pt/Ceria-Modified TiO2 and Its Photocatalytic Activity for Water Splitting under Visible Light

Author

Kundu, Shankhamala, primary, Ciston, Jim, additional, Senanayake, Sanjaya D., additional, Arena, Dario A., additional, Fujita, Etsuko, additional, Stacchiola, Dario, additional, Barrio, Laura, additional, Navarro, Rufino M., additional, Fierro, Jose L. G., additional, and Rodriguez, José A., additional

Published
2012
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36. H2 oxidation versus organic substrate oxidation in non-heme iron mediated reactions with H2O2.

Author

Hassanpour, Azin, Acuña-Parés, Ferran, Luis, Josep M., Cusso, Olaf, Morales de la Rosa, Silvia, Campos-Martín, José Miguel, Fierro, Jose L. G., Costas, Miquel, Lloret-Fillol, Julio, and Mas-Ballesté, Rubén

Subjects
HYDROGEN peroxide, HYDROGEN oxidation, IRON oxidation, HEME, COMPUTATIONAL chemistry
Abstract

Herein we show that species generated upon reaction of α-[Fe(CF3SO3)2(BPMCN)] (BPMCN = N,N′-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane) with H2O2 (putatively [FeV(O)(OH)(BPMCN)]) is able to efficiently oxidize H2 to H2O even in the presence of organic substrates, while species formed in the presence of acetic acid (putatively [FeV(O)(OAc)(BPMCN)]) prefer organic substrate oxidation over H2 activation. Mechanistic implications have been analysed with the aid of computational methods. [ABSTRACT FROM AUTHOR]

Published
2015
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44. Complete Chemical Hydrolysis of Cellulose into Fermentable Sugars through Ionic Liquids and Antisolvent Pretreatments.

Author

Morales‐delaRosa, Silvia, Campos‐Martin, Jose M., and Fierro, Jose L. G.

Subjects
CELLULOSE, MOLECULES, CHEMICALS, GLUCOSE, HYDROLYSIS
Abstract

This work describes a relatively simple methodology for efficiently deconstructing cellulose into monomeric glucose, which is more easily transformed into a variety of platform molecules for the production of chemicals and fuels. The approach undertaken herein first involves the dissolution of cellulose in an ionic liquid (IL), followed by a second reconstruction step aided by an antisolvent. The regenerated cellulose exhibited strong structural and morphological changes, as revealed by XRD and SEM analyses. These changes dramatically affect the hydrolytic reactivity of cellulose with dilute mineral acids. As a consequence, the glucose yield obtained from the deconstructed-reconstructed cellulose was substantially higher than that achieved through hydrolysis of the starting cellulose. Factors that affect the hydrolysis reaction include the type of cellulose substrate, the type of IL used in pretreatment, and the type of acid used in the hydrolysis step. The best results were obtained by treating cellulose with IL and using phosphotungstic acid (0.067 mol L−1) as a catalyst at 413 K. Under these conditions, the conversion of cellulose was almost complete (>99 %), with a glucose yield of 87 % after only 5 h of reaction. [ABSTRACT FROM AUTHOR]

Published
2014
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