Examinando por Autor "Ruiz-Garcia, Cristina"

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Hollow nitrogen- and boron-doped carbon submicrospheres with a porous shell. Preparation and application as supports for hydrodechlorination catalysts
(ACS, 2017) Alonso-Morales, Noelia; Ruiz-Garcia, Cristina; Palomar, Jose; Heras, Francisco; Calvo, Luisa; Rodriguez, Juan J.; Gilarranz, Miguel A.
Nitrogen- or boron-doped carbon submicrospheres with a hollow core and a porous shell were prepared via a template method and tested as supports for Pd/C catalysts. The carbon precursor was a phenol-formaldehyde resin that was generated into a silica template using pyridine, 1,10-phenantroline, and sodium tetraphenylborate as doping agents. The nitrogen and boron atomic percentages in doped carbon reached 0.5–3.6 and 0.03–0.67, respectively. High specific areas of up to 1846 m2/g with an important contribution of mesopores were achieved. The prepared Pd catalysts (1% w) exhibited unique features due to the morphology, porous structure, and doping of the support. The active phase was well-dispersed as nanoparticles with narrow size distribution (<10 nm) in an outer shell with a thickness of 77–124 nm. The short diffusion path needed for reactants and the well-developed network of mesopores of the shell contributed to diminish mass-transfer constraints. The catalysts showed remarkable activity (50–76 mmol/g·min) in the batch aqueous-phase hydrodechlorination of 4-chlorophenol at 30 °C and 1 atm, with higher values for the catalysts based on doped supports. Doping also promoted the selectivity toward hydrogenation products, particularly in the case of nitrogen-doped supports. The effect of support doping was more important at the 60 °C reaction temperature. The activity was maintained upon reuse, but the selectivity to hydrogenation products decreased.
Toward a green way for the chemical production of supported graphenes using porous solids
(Royal Society of Chemistry, 2014-02-12) Ruiz-Garcia, Cristina; Darder, Margarita; Aranda, Pilar; Ruiz-Hitzky, Eduardo
Within the many contributions in relation to the preparation and applications of graphene, this article tries to offer a new perspective on the efforts toward the exploration of alternative routes that could make possible the chemical production of graphenes in a green context. In this way, it is discussed how the use of organic molecules from natural origin offers good opportunities but, in general, it requires the use of convenient supports for the generation of the desired graphene-like materials. It is also shown how the use of porous supports in combination with diverse natural precursors is an interesting strategy, commonly employed to prepare templated carbons, that could also offer an ecological and, in some cases, mass production route for the generation of supported-graphenes. An outlook on the relevance of these supported-graphenes is given based on various examples of applications of these materials without removal of the inorganic support.