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Soria-Sanchez M.,Spanish University for Distance Education (UNED) | Castillejos-Lopez E.,Institute Catalisis y Petroleum | Maroto-Valiente A.,Spanish University for Distance Education (UNED) | Pereira M.F.R.,University of Porto | And 2 more authors.
Applied Catalysis B: Environmental | Year: 2012

A study of the catalytic decolourisation of one textile dye by oxidation with H 2O 2, using different carbon materials as catalysts, is reported. Ten carbon solids, differing both in their texture-structure features and in their surface chemistry properties, were used for this purpose. These are two activated carbons, a high surface graphite, two structured nanomaterials (carbon nanofibres and carbon nanotubes), and the derivative samples prepared by oxidation of the pristines with nitric acid solutions. All these samples were characterised by determination of the nitrogen adsorption isotherms, thermogravimetric data, transmission electron microscopy, pH at the point of zero charge and chemical composition based on the X-ray photoelectron spectra. These carbon materials were evaluated as catalysts for the catalytic wet peroxide oxidation of C.I. Reactive Red 241 dissolved in water. Carbon nanotubes (CNTs) exhibit the highest performance in terms of activity for the catalytic wet peroxide oxidation, achieving a total removal of the dye after 90min in process. It appears that catalytic activity for this reaction is improved by the internal cylindrical mesopores of CNTs. However, when these hydrophobic CNTs are treated by incorporation of oxygen surface groups which increase their hydrophilic character, the high catalytic performance of CNTs largely disappears. © 2012 Elsevier B.V.


Soria M.A.,Institute Catalisis y Petroleum | Mateos-Pedrero C.,Institute Catalisis y Petroleum | Guerrero-Ruiz A.,Spanish University for Distance Education (UNED) | Rodriguez-Ramos I.,Institute Catalisis y Petroleum | Rodriguez-Ramos I.,Spanish University for Distance Education (UNED)
International Journal of Hydrogen Energy | Year: 2011

Analysis of the effect of adding small amounts of steam to the methane dry reforming feed on activity and products distribution was performed from thermodynamic equilibrium calculations of the system based on the Gibbs free energy minimization method. This analysis is supported by new insights from the direct experimental investigation of the influence of co-feeding with H 2O over a Ru/ZrO2-La2O3 catalyst. Activity measurements were carried out in a fixed-bed reactor but using the operating conditions applicable in a Pd membrane reactor, that is, at maximum reaction temperature below 550 °C. Experimental results were in good agreement with thermodynamics predictions. It was observed that the addition of H2O into the dry reforming feed strongly affects activity and products distribution. The co-feeding of steam resulted in increasing methane conversion and hydrogen yield but decreasing carbon dioxide conversion and carbon monoxide yield. At a given temperature, syngas composition (H 2/CO ratio) can be tuned by changing the amount of H2O co-fed. Interestingly the stability of the Ru/ZrO2-La 2O3 catalyst was improved by adding steam to the dry reforming reactant mixtures. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Perez-Cadenas M.,Spanish University for Distance Education (UNED) | Munoz-Andres V.,Spanish University for Distance Education (UNED) | Rodriguez-Ramos I.,Institute Catalisis y Petroleum | Rodriguez-Ramos I.,Spanish University for Distance Education (UNED) | And 2 more authors.
Journal of Nano Research | Year: 2012

Multiwall carbon nanotubes were grown inside the millimetric channels of commercial ceramic materials, cordierite monoliths, using a modified catalytic chemical vapor deposition method. Fe(CO) 5 liquid catalyst precursor was introduced in gas phase at the same time as the acetylene carbon source to allow a more uniform distribution of carbon nanotubes on the substrate surface. Different techniques were used for the characterization of the obtained multiwall carbon nanotubes such as scanning and transmission electron microscopies, N 2 adsorption isotherms, Raman spectroscopy and thermogravimetric analysis. The results show that the surface of the ceramic monolith is progressively covered with multiwall carbon nanotubes reaching total coverage for longer times under reaction. The carbon nanotubes were built up with a tree-like morphology. So, firstly larger carbon nanotubes are formed as the tree trunks on the cordierite surface, followed by the growing on them of narrower and longer nanotubes suggesting the tree branches. © (2012) Trans Tech Publications, Switzerland.


Castillejos E.,Institute Catalisis y Petroleum | Rodriguez-Ramos I.,Institute Catalisis y Petroleum | Sanchez M.S.,Spanish University for Distance Education (UNED) | Munoz V.,Spanish University for Distance Education (UNED) | Guerrero-Ruiz A.,Spanish University for Distance Education (UNED)
Adsorption | Year: 2011

This study illustrates the effect of the adsorbent porosity (activated carbon and high surface area graphite) on the phenol adsorption kinetics. We have developed an experimental system where on line analysis of the solution is carried out by an optic fiber probe introduced in the water solution and directly connected with the UV spectrometer. This experimental setup permits to be more precise in determining kinetic parameters, considering that measurements are taken each 20 seconds. Our results show that the choice of the particle diameter of the adsorbent is critical in the control of the adsorption process kinetic, while the porosity of the carbon materials appears to be less relevant. © 2010 Springer Science+Business Media, LLC.


Soria M.A.,Institute Catalisis y Petroleum | Mateos-Pedrero C.,Institute Catalisis y Petroleum | Rodriguez-Ramos I.,Institute Catalisis y Petroleum | Rodriguez-Ramos I.,Spanish University for Distance Education (UNED) | Guerrero-Ruiz A.,Spanish University for Distance Education (UNED)
Catalysis Today | Year: 2011

Three Ru catalysts supported on SiO2, ZrO2-SiO 2 and ZrO2-La2O3 have been prepared, characterized and tested in the methane steam reforming (SR) reaction, and for comparative purposes a Ni/SiO2 catalyst has also been studied. Conditions of catalytic studies have been selected for the subsequent application in a hydrogen extraction Pd membrane reactor. That is, reaction temperatures in the range of 400-550 °C and with different amounts of catalyst in order to work under and/or close to the equilibrium conversion conditions. All the supported Ru samples exhibit high catalytic activity and similar CO and H2 yields. Finally these catalysts are fully stable under reaction conditions at 550 °C for 15 h, while the Ni/SiO2 sample suffers a significant deactivation. The main deactivation process affecting this latter catalyst is the carbon deposition of partially dehydrogenated intermediates as detected by Raman spectroscopy. Hence, these Ru catalysts appear to be suitable for application combined with metallic (Pd) membrane. © 2011 Elsevier B.V. All rights reserved.


Castillejos-Lopez E.,Institute Catalisis y Petroleum | Bachiller-Baeza B.,Institute Catalisis y Petroleum | Guerrero-Ruiz A.,Spanish University for Distance Education (UNED) | Rodriguez-Ramos I.,Institute Catalisis y Petroleum
Thermochimica Acta | Year: 2013

The interaction of organic chemicals with the surface of carbon nanotubes has been studied by immersion calorimetry revealing significant differences in the properties when these materials are modified thermally or chemically. Therefore, multiwall carbon nanotubes have been synthesized using a chemical vapour deposition procedure and subsequently aliquots were treated with HNO3 at reflux, maintaining the reaction during different times, in order to incorporate oxygen surface groups, or were treated at 2873 K under inert atmosphere. The aim of this thermal treatment is to eliminate structural defects of the carbon nanostructures and to graphitize the amorphous carbon phases. These features were confirmed by high-resolution transmission electron microscopy. The immersion in organic compounds, including toluene, methanol and methylcyclohexane, of all these carbon nanotubes samples reveals that the surface properties are remarkably modified. Thus, the formation of different types of interaction, depending on the surface, gives place to changes in the immersion enthalpies. © 2012 Elsevier B.V. All rights reserved.

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