Uso de hardware libre en el laboratorio: soluciones de bajo costo

Se llama hardware libre a aquellos dispositivos de hardware cuyas especificaciones y diagramas esquemáticos son de acceso público, ya sea bajo algún tipo de pago, o de forma gratuita. La filosofía del software libre es aplicable a la del hardware libre, y por eso forma parte de la cultura libre

Eterificación de HMF con n-butanol usando ácidos de Preyssler másicos e incluídos en una matriz silícea

En nuestro grupo de investigación se han desarrollado diferentes procesos que involucran los ácidos de Preyssler (H14NaP5W30O110 y H14NaP5W29MoO110) como catalizadores para diferentes transformaciones de derivados de biomasa, especialmente furfural y 5-hidroximetilfurfural (HMF

Efficient Liquid-Assisted Grinding Selective Aqueous Oxidation of Sulfides Using Supported Heteropolyacid Catalysts

The present work reports the preparation of 40MoAl200 and its full characterization using a number of analytical techniques (XRD, TEM, TGA, BET, EDX). Liquid-assisted ball milling proved to be a key tool to achieve both the best efficiency of 40MoAl200 as a novel Keggin type catalyst in the selective sulfoxidation reaction and also for succeeding in its effective recovery and reuse. In addition, the liquid assisted grinding process was studied in detail evaluating the influence of different parameters such as frequency of rotation (rpm), number and size of the stainless steel balls used and reaction time. The use of aqueous hydrogen peroxide is essential as water proved to exert a crucial role to improve both yields and selectivity towards sulfoxide formation. The procedure was representatively extended to a number of substrates with the possibility to extend the scope of the system to produce sulfoxides in high yields (up to 95 %) and satisfactory selectivities (up to 80 %). The catalyst proved to be recoverable and reusable under the optimized reaction conditions. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei

Design of Fe-modified mesoporous nanostructures as efficient catalysts for microwave-assisted selective oxidations of sulfides

Redox catalysts modified with Fe were synthesized via wet impregnation of metal species loaded on SBA-15. The influence of a number of Fe precursors with distinctive counter-ions on the deposited metal species was studied. Materials were characterized by XRD, N2 physisorption, TEM, UV–vis DR, TPR and adsorption-desorption of pyridine followed by FT-IR. The redox properties were determined in the oxidation of diphenyl sulfide assisted by microwave irradiation. The reaction was carried out in ethanol as solvent and using Urea-H2O2 as oxidant, both chosen for their greener properties. Conversion and selectivity to diphenyl sulfoxide were found to be optimum when iron chlorides were employed as metal precursors in the synthesis. These iron sources led to the formation of nanoclusters in the surface, resulting in more available and exposed iron oxide sites and, in consequence, an enhanced oxidation potential and improved catalytic performance. Finally, these solids were reused after 4 reaction cycles without loss of their activity, corroborating in this way, the high stability of Fe species loaded into the silicate matrix. © 2021 Elsevier B.V

A green and reusable catalytic system based on silicopolyoxotungstovanadates incorporated in a polymeric material for the selective oxidation of sulfides to sulfones

Two vanadium-containing Keggin silicopolyoxotungsto compounds K5SiVW11O40 and K6SiV2W10O40 were synthesized and characterized. They were incorporated in a superporous hydrogel constitute by prop-2-enamide and propenoic acid as initial monomers and bis-acrylamide as cross-linking moiety. Materials were characterized by several techniques. According to FTIR and 51V MAS-NMR, the (SiVxW12-xO40)(4+x)- anions are the main species present in the hybrid materials. Additionally, they do not decompose during the preparation of the composite. XRD and SEM-EDX results suggest that (SiVxW12-xO40)(4+x)- anions were well dispersed in the support or present as amorphous phases. These materials were evaluated as catalysts in the oxidation of sulfides to sulfones, using an eco-friendly oxidant and mild reaction conditions. The hybrid materials with higher content of the heteropoly compound displayed a remarkable catalytic behaviour in the oxidation of diphenyl sulfide. Materials also exhibited a stable catalytic performance through consecutive reuses. Optimum reaction parameters established were subsequently translated to the oxidation of a sulfide of interest (dapsone) due to its pharmacological activities. © 202