Reactions of ethanol over CeO2 and Ru/CeO2 catalysts

The reaction of ethanol has been investigated on Ru/CeO2 in steady state conditions as well as with temperature programmed desorption (TPD). High resolution transmission electron microscopy (HRTEM) images indicated that the used catalyst contained Ru particles with a mean size of ca. 1.5 nm well dispersed on CeO2 (of about 12–15 nm in size). Surface uptake of ethanol was measured by changing exposure to ethanol followed by TPD. Saturation coverage is found to be between 0.25 and 0.33 of a monolayer for CeO2 that has been prior heated with O2 at 773 K. The main reactions of ethanol on CeO2 during TPD are: re-combinative desorption of ethanol; dehydrogenation to acetaldehyde; and dehydration to ethylene. The dehydration to ethylene occurs mainly in a small temperature window at about 700 K and it is attributed to ethoxides adsorbed on surface-oxygen defects. The presence of Ru considerably modified the reaction of ceria towards ethanol. It has switched the desorption products to CO, CO2, CH4 and H2. These latter products are typical reforming products. Ethanol steam reforming (ESR) conducted on Ru/CeO2 indicated that optimal reaction activity is at about 673 K above which CO2 production declines (together with that of H2) due to reverse water gas shift. This trend was well captured during ethanol TPD where CO2 desorbed about 50 K below than CO on both oxidized and reduced Ru/CeO2 catalysts.Peer ReviewedPostprint (author's final draft

Experiencia, empatía y conversión: una teología de la música como epifanía del Misterio.

En nuestro entorno cultural, la pregunta religiosa actual se formula en términos de «¿cómo decir Dios?». Esta búsqueda se concreta privilegiadamente en el ámbito de la experiencia estética. En este horizonte, el autor ensaya elaborar una teología de la música como epifanía del Misterio partiendo de la experiencia, la empatia y la conversión. Se subraya la presencia de compositores que interpretan hermenéuticamente la Palabra llevándola a una comprensión empática y que va más allá de cualquier explicación. A la hora de decir una palabra sobre el Inefable y sobre el misterio de su comunicabilidad, los teólogos pueden ser sensibles a los lenguajes meta-lingüísticos, como la música y la percepción estética. En ellos pueden encontrar un camino de comunicación de la percepción estética del Misterio del Dios que se revela

Gestión de residuos a lo largo del ciclo de vida de un automóvil

El estudio que se desarrolla a continuación tiene el objetivo de analizar los sectores y procesos de reciclaje de los residuos generados por un vehículo a lo largo desu vida útil. Se pretende detectar posibles lagunas  existentes en la actualidad y proponer mejoras organizativas según las carencias detectadas. Este estudio se realiza en definitiva, analizando el sector automovilístico y el reciclaje que se lleva acabo en el mismo, teniendo en cuenta la aplicación de la Directiva Europea2000/53 en el Estado Español y repasando los procesos de reciclaje de los diferentes componentes de un vehículo.  Mediante las carencias detectadas en dichos procesos se propone la mejora de la gestión de los residuos en los talleres con la creación de un SIG (Sistema Integrado de Gestión)

Hall-Petch strengthening of the constrained metallic binder in WC-Co cemented carbides: Experimental assessment by means of massive nanoindentation and statistical analysis

WC–Co cemented carbides are geometrically complex composites constituted for two interpenetrating networks of the constitutive ceramic and metal phases. Accordingly, assessment of microstructural effects on the local mechanical properties of each phase is a challenging task, especially for the metallic binder. In this work, it is attempted by combining massive nanoindentation, statistical analysis, and implementation of a thin film model for deconvolution of the intrinsic hardness and flow stress of the metallic phase. Plotting of yield stress values as a function of the binder mean free path results in a Hall-Petch strengthening relationship with a slope (ky) of 0.98 MPa m1/2. This value points out the effectiveness of WC–Co phase boundaries as strong obstacles to slip propagation; and thus, for toughening of the brittle phase (WC) by means of crack-bridging ductile (Co) reinforcement.Peer ReviewedPostprint (author's final draft

The Upper Neoproterozoic-Lower Cambrian continental extension in the Anti-Atlas (Morocco)

Dans l’Anti-Atlas (sud du Maroc), la couverture du Néo-protérozoïque supérieur, discordante sur les structures panafricaines, s’organise en « séries » volcaniques et détritiques (Groupe du Saghro et de Ouarzazate), recouvertes par les dépôts carbonatés cambriens. De nouvelles observations réalisées dans cette couverture montrent qu’elle résulte d’un épisode extensif dont témoignent, outre les structures extensives, des mises en place de magmas et des manifestations hydrothermales. Cet épisode, qui se maintiendra jusqu’au Cambrien inférieur, est interprété en termes d’extension continentale post-panafricaine

Assessment of kinetic model for ceria oxidation for chemical-looping CO2 dissociation

Chemical looping technologies are identified as to have an excellent potential for CO2 capture and fuels synthesis. Oxygen carriers are the fundamental component of a chemical looping process, and the choice of stable and efficient carriers with fast redox kinetics is the key to the successful design of the process. Hence, understanding the reaction kinetics is of paramount importance for the selection of an appropriate oxygen carrier material. This work provides a method for kinetic model selection based on a statistical approach to identify the reaction mechanism. The study experimentally investigates the oxidation kinetics of CeO2-d by CO2 and applies a statistical method for the selection of the best-fitting kinetic model for the reaction. The kinetic study is performed in the temperature range of 700–1000¿°C with a CO2 concentration between 20 and 40¿vol% in the feed. The measured peak rates of CO production on ceria were influenced both by temperature and concentration of reactant. The total CO production was more influenced by the temperature than by CO2 concentration, with a maximum CO yield of 33.66¿ml/g at 1000¿°C and 40% CO2. The identification of the oxidation kinetic model is performed by fitting different reactions models to the measured reaction rates and statistically comparing them using the Residual sum of squares (RSS), Akaike information criterion (AICc) and the F-test for the selection of the best-fitting one. Models corresponding to the nucleation and grain growth reaction mechanism provided a good fit of the data, with the Sestak-Berggren (SB) model showing the best approximation of the measured rate of reaction with an evaluated activation energy of 79.1¿±¿6.5¿kJ/mol for the CO2 oxidation.Peer ReviewedPostprint (author's final draft

ITalian Geomagnetic Reference Field (ITGRF): update for 2000 and secular variation model up to 2005 by autoregressive forecasting

The updated version of the ITalian Geomagnetic Reference Field (ITGRF) for 2000.0 and its secular variation model up to 2005.0 are presented in this paper. The main field model is based on a simple polynomial approximation in latitude and longitude of the geomagnetic field elements computed from IGRF on a 12° ¥ 11° grid centred over Italy. The annual means from L'Aquila observatory were used to determine the baseline level, imposing a constant observatory anomaly bias. This procedure gives a set of 6 coefficients every 5 years from 1960 to 2005 for the horizontal H, total field F, vertical Z and declination D elements of the geomagnetic field. The extrapolation of ITGRF to 2005 is based on an autoregressive forecasting of the L'Aquila observatory annual means. Comparison of the field values computed from the model with those recorded at the other Italian observatory (Castello Tesino) shows that the ITGRF improves the fit of the secular variation pattern with respect to the global IGRF model by a factor of 3. The ITGRF represents a reliable alternative to global models when reducing magnetic surveys to a common reference epoch over the Italian region