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RUA (125.261 recursos)

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INV - NNM - Artículos de Revistas

Mostrando recursos 1 - 7 de 7

  1. The role of mesoporosity and Si/Al ratio in the catalytic etherification of glycerol with benzyl alcohol using ZSM-5 zeolites

    Gonzalez-Arellano, Camino; Grau-Atienza, Aida; Serrano, Elena; Romero, Antonio A.; Garcia-Martinez, Javier; Luque, Rafael
    A comparative study of the influence of three different acid solids as catalysts (conventional zeolites Z15c with Si/Al = 19.5 and Z40c with Si/Al = 48.2, and a hierarchical zeolite Z40c-H with Si/Al = 50.0) for the etherification of glycerol with benzyl alcohol was performed. The catalytic activity and selectivity of these zeolites was elucidated at different catalyst contents. Three different ethers (3-benzyloxy-1,2-propanediol, which is a mono-benzyl-glycerol ether (MBG) and 1,3-dibenzyloxy-2-propanol, which is a di-benzyl-glycerol ether (DBG) and dibenzyl ether (DBz) were identified as the main products. MBG was the major product of the reaction catalyzed by the microporous Z15c...

  2. Mesoporous Metal Complex–Silica Aerogels for Environmentally Friendly Amination of Allylic Alcohols

    Grau-Atienza, Aida; Baeza, Alejandro; Serrano, Elena; Garcia-Martinez, Javier; Nájera, Carmen
    Two series of mesoporous hybrid iron(III) complex–silica aerogels were prepared in one-pot synthesis by using the sol–gel coordination chemistry approach. The use of the ligands 3-(2-aminoethylamino)propyltrimethoxysilane and 2-(diphenylphosphino)ethyltriethoxysilane, both with terminal triethoxysilyl groups, were used to incorporate metal complexes in situ into the framework of silica, through their co-condensation with a silicon alkoxide during the aerogel formation. This methodology yielded optically translucent hybrid mesoporous gels with homogeneous metal incorporation and excellent textural properties. The catalytic performance of these materials was tested in the direct amination of allylic alcohols in water as a target reaction, with activities comparable or even higher than...

  3. Magnetically separable mesoporous Fe3O4/silica catalysts with very low Fe3O4 content

    Grau-Atienza, Aida; Serrano, Elena; Linares Pérez, Noemí; Svedlindh, Peter; Seisenbaeva, Gulaim; Garcia-Martinez, Javier
    Two magnetically separable Fe3O4/SiO2 (aerogel and MSU-X) composites with very low Fe3O4 content (<1 wt%) have been successfully prepared at room temperature by co-condensation of MPTES-functionalized Fe3O4 nanoparticles (NPs) with a silicon alkoxide. This procedure yields a homogeneous incorporation of the Fe3O4 NPs on silica supports, leading to magnetic composites that can be easily recovered using an external magnetic field, despite their very low Fe3O4 NPs content (ca. 1 wt%). These novel hybrid Fe3O4/SiO2 materials have been tested for the oxidation reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) with hydrogen peroxide showing an enhancement of the stability of the NPs in the Fe3O4/silica...

  4. Insights into the Active Species of Nanoparticle-Functionalized Hierarchical Zeolites in Alkylation Reactions

    Grau-Atienza, Aida; Campos, Rafael; Serrano, Elena; Ojeda, Manuel; Romero, Antonio A.; Garcia-Martinez, Javier; Luque, Rafael
    Supported iron oxide nanoparticles have been incorporated onto hierarchical zeolites by microwave-assisted impregnation and mechanochemical grinding. Nanoparticle-functionalised porous zeolites were characterised by a number of analytical techniques such as XRD, N2 physisorption, TEM, and surface acidity measurements. The catalytic activities of the synthesised nanomaterials were investigated in an alkylation reaction. The results pointed to different species with varying acidity and accessibility in the materials, which provided essentially different catalytic activities in the alkylation of toluene with benzyl chloride under microwave irradiation, selected as the test reaction.

  5. Effect of the polymer shell in imidazole microencapsulation by solvent evaporation method

    Fuensanta, Mónica; Grau-Atienza, Aida; Romero Sánchez, María Dolores; Guillem, Celia; López Buendía, Ángel M.
    In this paper, the microencapsulation of imidazole derivatives (1-methylimidazole and 2-phenylimidazole, 1-MIm and 2-PhIm, respectively) as core materials into polymeric shells has been studied. Imidazoles are used as latent curing agents for epoxy resins with application for example in the manufacturing of electronic devices. Microencapsulation of imidazoles has been carried out by solvent evaporation and different experimental parameters (e.g. type of polymer for the shell) have been analyzed and the final properties of the capsules obtained (particle size, morphology or thermal properties). Characterization has been carried out using differential scanning calorimetry (DSC) and thermal gravimetry analysis (TGA) for the thermal...

  6. Desilication of TS-1 zeolite for the oxidation of bulky molecules

    Silvestre Albero, Ana; Grau-Atienza, Aida; Serrano, Elena; Garcia-Martinez, Javier; Silvestre-Albero, Joaquín
    A series of modified TS-1 samples have been produced by desilication of the original TS-1 (4 wt.% Ti) using a chemical treatment with NaOH. Desilicated TS-1 zeolites exhibit a large BET surface area together with a well-developed mesoporosity. The hierarchical catalysts from desilication of TS-1 zeolite show a good catalytic activity for the oxidation of small molecules and a significantly higher activity for the oxidation of bulky molecules.

  7. Bistable spin-crossover nanoparticles showing magnetic thermal hysteresis near room temperature

    Coronado, Eugenio; Galá Mascarós, Jose Ramón; Monrabal Capilla, María; Garcia-Martinez, Javier; Pardo Ibáñez, Pablo
    We have demonstrated that the reverse micelle technique can be applied to polymeric spin-crossover systems, such as [Fe(Htrz)2(trz)](BF4), to control the growth of the crystallites. Small nanoparticles of diameters around 10 nm and narrow size distribution were obtained. It is easy to envision that, by modifying the synthetic procedure, the size and critical temperatures of these nanoparticles can be tuned. On one hand, different ratios of solvent, water, and surfactants will lead to different micelle sizes, which will affect the particle size and, maybe, the magnetic properties. On the other hand, the critical temperatures can be lowered towards room temperature by changing the composition of the nanoparticles. Indeed, on doping the [Fe(Htrz)2(trz)](BF4)...

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