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Christoforidis K.C.,Institute Catalisis y Petrolequimica CSIC | Iglesias-Juez A.,Institute Catalisis y Petrolequimica CSIC | Figueroa S.J.A.,European Synchrotron Radiation Facility | Di Michiel M.,European Synchrotron Radiation Facility | And 2 more authors.
Catalysis Science and Technology | Year: 2013

The structural (from local to long range order) and electronic evolution of Fe-doped anatase nanomaterials is evaluated using in situ synchrotron based X-ray total scattering/diffraction and absorption techniques and Raman spectroscopy. These methods are combined with UV-visible spectroscopy and infrared diffuse reflectance (DRIFTS) to maximize the level of structural and morphological information regarding these materials. Fe doping of anatase nanomaterials generates solids having Fe at substitutional positions of the structure, and anion vacancies as charge neutrality entities. These structural modifications lead to materials with decreasing band gap energy as a function of Fe content. Concomitantly, mid-gap electronic states are observed to appear. At the same time, the presence of Fe alters the primary particle shape of the anatase without changing significantly the primary particle size. In contrast with previous results, analysis of the combined results strongly indicates that UV and visible photocatalytic activity are here dominated by morphological rather than structural/electronic issues. © The Royal Society of Chemistry 2013.

Kubacka A.,Institute Catalisis y Petrolequimica CSIC | Iglesias-Juez A.,Institute Catalisis y Petrolequimica CSIC | Martinez-Arias A.,Institute Catalisis y Petrolequimica CSIC | Di Michiel M.,European Synchrotron Radiation Facility | And 2 more authors.
ChemCatChem | Year: 2012

The evolution of time-resolved experiments, covering a multipurpose surface and bulk characterization of catalytic solids, during their preparation process and under reaction conditions, is presented. Particular emphasis is given to recent studies that attempt to unveil contemporary unresolved questions concerning the control of physicochemical properties of nanosolids, as well as the evolution of such solid materials under reactive atmospheres. To reach this goal, representative insitu and inoperando works, using either modern (mostly synchrotron radiation based) approaches or multi-technique methods (mainly, although not exclusively, X-ray-vibrational coupling), and considering experiments in liquid and gas phase, as well as with amorphous, nanocrystalline and surface-deposited materials, are reviewed. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sadaba I.,Institute Catalisis y Petrolequimica CSIC | Sadaba I.,Haldor Topsøe | Ojeda M.,Institute Catalisis y Petrolequimica CSIC | Ojeda M.,BP Chemicals Ltd | And 2 more authors.
Applied Catalysis B: Environmental | Year: 2014

This investigation reports on the catalytic properties and hydrothermal stability of hybrid organic-inorganic nanocomposites based on aminopropyl-functionalised SiO2 and poly(styrenesulphonic acid) (PSSA). The nanocomposites were characterised by chemical analysis, thermogravimetric analysis (TGA), N2 adsorption-desorption isotherms, transmission electron microscopy (TEM), as well as Raman, Diffuse Reflectance Infrared Fourier Transform (DRIFT), X-ray Photoelectron (XPS) and 1H and 13C solid Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR) spectroscopies. The results have proved that the presence of amino-functionalised silica results in stabilisation of the polymer molecules within the particle network of SiO2. The polymer is anchored to the silica matrix via electrostatic interactions between the sulphonic groups of the polymer molecules and the amino-functions present in the silica. These nanocomposites exhibited promising catalytic activity in xylose dehydration to furfural (at 443K and after 5h, ca. 90% xylose conversion, 65% furfural selectivity). When reused for several cycles, deactivation during the first run was observed due to polymer leaching. In successive runs catalytic properties remain stable. © 2013 Elsevier B.V.

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