Examinando por Autor "Morere, Jacobo"

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Deposition of Ni nanoparticles onto porous supports using supercritical CO2: effect of the precursor and reduction methodology
(The Royal Society, 2015-12-28) Morere, Jacobo; Royuela, Sergio; Asensio, Guillermo; Palomino, Pablo; Enciso, Eduardo; Pando, Concepción; Cabañas, Jacobo
The deposition of Ni nanoparticles into porous supports is very important in catalysis. In this paper, we explore the use of supercritical CO2 (scCO2) as a green solvent to deposit Ni nanoparticles on mesoporous SiO2 SBA-15 and a carbon xerogel. The good transport properties of scCO2 allowed the efficient penetration of metal precursors dissolved in scCO2 within the pores of the support without damaging its structure. Nickel hexafluoroacetylacetonate hydrate, nickel acetylacetonate, bis(cyclopentadienyl)nickel, Ni(NO3)2⋅6H2O and NiCl2⋅6H2O were tried as precursors. Different methodologies were used: impregnation in scCO2 and reduction in H2/N2 at 400°C and low pressure, reactive deposition using H2 at 200–250°C in scCO2 and reactive deposition using ethanol at 150–200°C in scCO2. The effect of precursor and methodology on the nickel particle size and the material homogeneity (on the different substrates) was analysed. This technology offers many opportunities in the preparation of metal-nanostructured materials.
Deposition of Pd into mesoporous silica SBA-15 using supercritical carbon dioxide
(Elsevier, 2011-03) Morere, Jacobo; Tenorio, María José; Torralvo, María José; Pando, Concepción; Rodríguez Renuncio, Juan Antonio; Cabañas, Albertina
Designing nanocomposites using supercritical CO2 to insert Ni nanoparticles into the pores of nanopatterned BaTiO3 thin films
(Royal Society of Chemistry, 2016) Castro, Alichandra; Morere, Jacobo; Cabañas, Albertina; Ferreira, Liliana P.; Godinho, Margarida; Ferreira, Paula; Vilarinho, Paula M.
A new concept to prepare nanocomposite thin films is explored. Two chemical-based bottom-up steps are used to design functional films including (i) the block copolymer-assisted self-assembly of a porous matrix; and (ii) the impregnation of nanoparticles from a ferroic phase into the pores by supercritical CO2 deposition. Porous nanopatterned BaTiO3 thin films with ca. 17 nm thickness are prepared using a cost-effective sol–gel solution containing a block copolymer and evaporation-induced self-assembly methodology. Hexagonally arranged pores with a diameter of ca. 95 nm, running perpendicular to the substrate, are filled with Ni nanoparticles using the supercritical fluid deposition technique, obtained from the reduction of hydrated nickel nitrate in a supercritical CO2–ethanol mixture at 250 °C. Small Ni nanoparticles of 21 ± 5 nm size are selectively deposited inside the pores of the porous matrix. Structural and magnetic properties prove the coexistence of both phases.
Role of excess molar enthalpies in supercritical antisolvent micronizations using dimethylsulfoxide as the polar solvent
(Elsevier, 2011-12) Zahran, Fouad; Morere, Jacobo; Cabañas, Albertina; Rodríguez Renuncio, Juan Antonio; Pando, Concepción
Solubility of two metal-organic ruthenium precursors in supercritical CO2 and their application in supercritical fluid technology
(Elsevier, 2012-03) Morere, Jacobo; Tenorio, María José; Pando, Concepción; Rodríguez Renuncio, Juan Antonio; Cabañas, Albertina
Supercritical fluid deposition of Ru nanoparticles onto SiO2 SBA-15 as a sustainable method to prepare selective hydrogenation catalysts
(Royal Society of Chemistry, 2015) Morere, Jacobo; Torralvo, María José; Pando, Concepción; Rodríguez Renuncio, Juan Antonio; Cabañas, Albertina
Ru nanoparticles were successfully deposited onto mesoporous SiO2 SBA-15 using supercritical CO2 (scCO2). The use of scCO2 favoured the metal dispersion and Ru nanoparticles uniformly distributed throughout the support were obtained. Different precursors and methodologies were employed: impregnation with Ru(tmhd)2(COD) in scCO2 at 80 °C and 13.5 and 19.3 MPa and further reduction in H2/N2 at 400 °C at low pressure, reactive deposition of Ru(tmhd)2(COD) with H2 in scCO2 at 150 °C and reactive deposition of RuCl3·xH2O with ethanol in scCO2 at 150 and 200 °C. The size of the particles was limited in one dimension by the pore size of the support. The metal loading varied with the methodology and experimental conditions from 0.9 to 7.4% Ru mol. These materials exhibited remarkable catalytic activity. The Ru/SiO2 SBA-15 materials prepared by reactive deposition with H2 in scCO2 were selective catalysts for the hydrogenation reactions of benzene and limonene, allowing the production of partly hydrogenated hydrocarbons that may serve as building blocks for more complex chemicals. scCO2 is shown to be a green solvent that allows the preparation of efficient heterogeneous catalysts to design sustainable processes. Furthermore, in the hydrogenation of limonene, scCO2 was also used as the solvent.
Supercritical fluid preparation of Pt, Ru and Ni/graphenenanocomposites and their application as selective catalysts in thepartial hydrogenation of limonene
(Elsevier, 2017-02) Morere, Jacobo; Sánchez-Miguel, Elizabeth; Tenorio, María José; Pando, Concepción; Cabañas, Albertina
The development of new materials and methods to prepare selective hydrogenation catalysts is essential from both environmental and economic reasons due to their industrial applications. In this context, the use of reduced graphene oxide (rGO) as a metal-free catalyst and catalytic support is explored. Thanks to the penetrating and exfoliating ability of supercritical CO2 (scCO2), Pt, Ru and Ni nanoparticles were homogeneously deposited on rGO through a sustainable method. Particle size for the different metal/rGO varied from 2 to 15 nm depending on the metal, methodology and metal loading (1–7% wt.). The Pt/rGO and Ru/rGO materials prepared in scCO2 were used as catalysts in the hydrogenation of limonene. The reaction was performed in CO2 at supercritical conditions. All the metal/rGO catalysts showed high activities and selectivities of ca. 90% to the partially hydrogenated form, p-menthene, that kept constant with reaction time. The Ru/rGO catalyst was reused up to 4 times with minor loss of activity and constant selectivity. The high activity and selectivity may be related to the 2D open structure of the support, which favours adsorption of reactants and desorption of intermediate products.
Thiol group functionalization of mesoporous SiO2 SBA-15 using supercritical CO2
(Elsevier, 2018) Tenorio, Maria Jose; Morere, Jacobo; Carnerero, Cyntia; Torralvo, Maria Jose; Pando, Concepcion; Cabañas, Albertina
Chemical modification of mesoporous SiO2 SBA-15 with thiol groups was performed using mercaptopropyltrimethoxysilane (MPTMS) dissolved in supercritical CO2 (scCO2). Thiol groups serve as adsorbents for the selective removal of contaminant metal cations and in catalysis. Functionalization was carried out in scCO2 at temperatures ranging from 40 to 150 C and pressures from 15.0 to 29.0 MPa. For comparison purposes, the reaction was also performed in toluene at 80 and 110 C. As opposed to toluene, scCO2 is considered a green solvent. Grafting of the thiol groups was confirmed by FTIR spectroscopy, thermogravimetric analysis (TGA) and elemental analysis. Grafting density and surface coverage of the materials modified using scCO2 increased with temperature, CO2 density, time and stirring and varied from 1.3 to 4.4 mmol/ g and from 1.3 to 4.0 molecules/ nm, respectively. On the other hand, surface area and pore size decreased as grafting density increased. At temperatures of 80 C or higher, the pore size remained constant, suggesting the formation of a compact monolayer. Modification at higher temperatures led to larger grafting densities but very low surface areas. Assuming total hydrolysis and condensation of the precursor, the optimum grafting density and surface coverage of 2.3 mmol/ g and 2.4 molecules/ nm, respectively, were obtained in scCO2 at 80 C and 25.0 MPa for 4 h. Grafting densities of the samples prepared in toluene were by far much lower than those obtained using scCO2 at lower temperatures and shorter times, which demonstrates the advantages of CO2 as a green functionalization medium.