Person: Pando García-Pumarino, Concepción
Universidad Complutense de Madrid
Faculty / Institute
Now showing 1 - 2 of 2
PublicationThiol group functionalization of mesoporous SiO2 SBA-15 using supercritical CO2(Elsevier, 2018-08-02) Tenorio, M.J.; Carnerero, C.; Torralvo Fernández, María José; Pando García-Pumarino, Concepción; Cabañas Poveda, AlbertinaChemical 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 scCO2increased with temperature, CO2 density, time and stirring and varied from 1.3 to 4.4 mmol g−1 and from 1.3 to 4.0 molecules nm−2, 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−1 and 2.4 molecules nm−2, 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. PublicationSupercritical fluid deposition of Ru nanoparticles into SiO2 SBA-15 as a sustainable method to prepare selective hydrogenation catalysts(RSC, 2015) Morère Rodríguez, Jacobo; Torralvo Fernández, María José; Pando García-Pumarino, Concepción; Rodríguez Renuncio, Juan Antonio; Cabañas Poveda, AlbertinaRu nanoparticles were successfully deposited into 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 ºC and 13.5 and 19.3 MPa and further reduction in H2/N2 at 400 ºC at low pressure, reactive deposition of Ru(tmhd)2(COD) with H2 in scCO2 at 150 ºC and reactive deposition of RuCl3•xH2O with ethanol in scCO2 at 150 and 200 ºC. 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.