Carbon materials as template for the preparation of mixed oxides with controlled morphology

Resumen del libro de actas del Congreso: 5th Czech-Italian-Spanish Conference on Molecular Sieves and Catalysis, celebrado en Segovia del 16 al 19 de junio de 2013Bulk mixed oxide catalysts are widely used for many applications, such as catalysts for selective oxidation processes, electrocatalysts for fuel cells, gas sensors, and solid oxide electrolysers for the production of hydrogen. VPO (vanadium and phosphorous oxides) are one of the bulk mixed oxide materials which are of interest nowadays since they are active catalysts for saturated hydrocarbon activation. With the conventional synthesis procedures for preparing bulk mixed oxides is really difficult to control the morphology and the porous structure of these materials. In practice, there are just a few works about the synthesis of mixed oxide materials with controlled morphology. The aim of this work was to describe new approaches for the preparation of VPO mixed oxides materials with spherical morphology. A carbon material was prepared using cellulose as starting material by hydrothermal treatment with phosphoric acid at 200ºC and carbonized at 500ºC. SEM analysis showed that carbon spheres with diameter up to 0.5 m were prepared by this procedure. These phosphorous containing carbon material was impregnated with the appropriate amount of vanadium oxide species in order to obtain a monolayer of VOx species on the surface of the carbon materials following a procedure described previously (1). By this manner, a carbon supported VOx material with spherical morphology was obtained (VPO/Csph). The calcination of this material was optimized in order to obtain VPO spheres with diameter up to 1-2 m and with BET area values close to 100 m2/g. Figure 1 shows a SEM image of this sample (VPOsph). The presence of vanadium pyrophosphate phase, which has been described as the active phase of this catalytic system, was identified by XRD and Raman spectroscopy. Thus, the chemical composition as well as the morphology and porous structure of these new spherical materials makes them quite promising as catalysts

Kinetic study of methanol dehydration over Zro2 supported-activated carbons

The growing concerns about climate change and energy consumption have been the driving force in seek of alternative fuels such as DME, mainly produced via methanol dehydration over a solid acid catalyst. The use of activated carbons for this aim has been little studied up to date. Only a few studies can be found in the literature, reporting all of them materials with a low thermal stability of the acid surface groups, which results into a fast deactivation of the catalyst. In this work, the preparation of activated carbons via chemical activation with phosphoric acid, their modification with different ZrO2 loads, and their application as methanol dehydration catalysts have been studied. The catalytic results showed that the best methanol conversion and selectivity towards DME were achieved with the activated carbon prepared with an impregnation mass ratio value (H3PO4 /precursor) of 2 and an activation temperature of 800 ºC, loaded with a 7 % (wt) of ZrO2 . This catalyst exhibits high steady state methanol conversion values even at temperatures as high as 400 ºC (XCH3OH= 80%, 0.1 g·s/μmol, PCH3OH= 0.08 atm in helium), keeping a selectivity to DME higher than 96%. The effect of oxygen in the reaction atmosphere was also analysed. In this sense, an increase of 15 % in the DME yield was obtained when using air instead of helium as reaction atmosphere (350 ºC, 0.1 g·s/μmol, PCH3OH= 0.04 atm). A kinetic study has been carried out on this catalyst in which two mechanisms (Eley Rideal and Langmuir Hinshelwood) for methanol dehydration have been analysed. The models proposed also consider the presence of oxygen in the reaction media.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO (CTQ2015-68654-R). MECD (FPU13/02413)

Perceveid Social Support in middle school students

Research on school climate has among its purposes to contribute to improving the quality of education, one of the main challenges of the Mexican educational system, particularly at the level of basic education. Our aim was to explore the relationships between the dimensions of school climate of perceived social the support teacher-student, support student-student and opportunities for autonomy and academic performance. The study was non-experimental and correlational. The sample consisted of 325 students from a middle school in northeastern Mexico, with a mean age of 13.4 years who responded to a scale of perceived school climate. The results show that students perceive great teacher support associated with student-student support and opportunities for autonomy. In addition, we found that academic achievement related to teacher support and opportunities for autonomy. These data are consistent with the country´s educational policy, which emphasizes the teacher´s role as facilitator of student learning to improve learning outcomes and the quality of education.Fil: Rodriguez, María Concepción. Universidad Autónoma de Nuevo León; MéxicoFil: Vivas, Jorge Ricardo. Universidad Nacional de Mar del Plata. Facultad de Psicología. Centro de Investigación en Procesos Básicos, Metodologías y Educación; ArgentinaFil: Comesaña, Ana. Universidad Nacional de Mar del Plata. Facultad de Psicología. Centro de Investigación en Procesos Básicos, Metodologías y Educación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Ramirez, Laura Minerva. Universidad Autónoma de Nuevo León; MéxicoFil: Peña, José Armando. Universidad Autónoma de Nuevo León; Méxic

El efecto de la descentralización del sector público sobre la deuda pública de los países

El endeudamiento excesivo de los gobiernos subcentrales se considera uno de los peligros de la descentralización fiscal. Por otra parte, la descentralización podría garantizar la estabilidad fiscal del sector público al restringir los gobiernos “Leviatánicos”. Dado que el impacto de la descentralización fiscal sobre la deuda pública y sobre los resultados fiscales es ambiguo desde un punto de vista teórico, se analiza esta cuestión empíricamente con un panel de 8 países federales y cuasifederales, con medidas solo regionales de la descentralización para el período 1990-2011, y otro panel de 18 países federales y no federales, con medidas tanto regionales como locales de la descentralización para el periodo de 1980-2011. Nuestros hallazgos sugieren que la descentralización regional aumenta la deuda pública, mientras que la descentralización local la reduce. Asimismo, el tamaño del Sector Público también incrementa dicha deuda, mientras que el saldo primario parece tener una relación negativa, siendo las demás variables no significativas.Excessive borrowing by subnational governments is considered to be one of the perils of fiscal decentralization. On the other hand, fiscal decentralization might ensure the fiscal stability of the public sector by constraining Leviathan governments. Since the impact of decentralized government on fiscal outcomes is therefore ambiguous from a theoretical perspective, we explore this question empirically with a panel of 8 federal countries, with only regional decentralization measures over 1990-2001 period, and another panel of federal and non-federal countries, both regional and local measures of decentralization over the 1980-2011 period. Our findings suggest that regional decentralization increases public debt, while local decentralization reduces it. Also, the size of Public Sector increases the debt, while the primary balance seems to have a negative relationship, with no other significant variables

Making more flexible ATISMART+ model for traffic simulations using a CAS

Traffic simulations usually require the search of a path to join two different points. Dijkstra’s algorithm [1] is one of the most commonly used for this task due to its easiness and quickness. In [2, 3] we developed an accelerated time simulation of car traffic in a smart city using Dijkstra’s algorithm to compute the paths. Dijkstra’s algorithm provides a shortest path between two different points but this is not a realistic situation for simulations. For example, in a car traffic situa- tion, the driver may not know the shortest path to follow. This ignorance can be produced, among others, because one of the following two facts: the driver may not know the exact length of the lanes, or, even knowing the exact length, the driver may not know how to find the shortest path. Even more, in many cases, a mixture of both facts occurs. A more realistic simulation should therefore consider these kind of facts. The algorithm used to compute the path from one point to another in a traffic simulation might consider the possibility of not using the shortest path. In this talk, we use a new probabilistic extension of Dijkstra’s algorithm which covers the above two situations. For this matter, two different modifications in Di- jkstra’s algorithm have been introduced: using non-exact length in lanes, and the choice of a non-shortest path between two different points. Both modifications are used in a non-deterministic way by means of using probability distributions (classi- cal distributions such as Normal or Poisson distributions or even "ad hoc" ones). A precise, fast, natural and elegant way of working with such probability distributions is the use of a CAS in order to deal with exact and explicit computations. As an example of use of this extension of Dijkstra’s algorithm, we will show the ATISMART+ model. This model provides more realistic accelerated time sim- ulations of car traffics in a smart city and was first introduced in [4] and extended in [5]. This model was developed combining J AVA for the GUI and M AXIMA for the mathematical core of the algorithm. The studies developed in the above mentioned works, dealt with Poisson, Ex- ponential, Uniform and Normal distributions. In this talk we will introduce, as a novelty, the possibility of using other continuous probability distributions such as: Lognormal, Weibul, Gamma, Beta, Chi-Square, Student’s t, Z, Pareto, Lo- gistic, Cauchy or Irwin-Hall, and other discrete distributions such as: Bernouille, Rademacher, Binomial, Geometric, Negative Binomial or Hypergeometric. Even 1 more, this new version allows to deal with any “ad-hoc” continuous, discrete or mixed user’s distributions. This fact improves the flexibility of ATISMART+ model.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Methanol dehydration on carbon-based acid catalysts

Methanol dehydration to produce dimethyl ether (DME) is an interesting process for the chemical industry since DME is an important intermediate and a promising clean alternative fuel for diesel engines. Pure or modified γ-aluminas (γ-Al2O3) and zeolites are often used as catalysts for this reaction. However, these materials usually yield non desirable hydrocarbons and undergo fast deactivation. In this work, we study the catalytic conversion of methanol over an acid carbon catalyst obtained by chemical activation of olive stone with H3PO4. A significant amount of phosphorus remains over the catalyst surface after the activation process, mostly in form of C-O-PO3 and C-PO3 groups, which provide the carbon a relatively high surface acidity and oxidation resistance. Methanol decomposition on this catalyst yields selectivities to DME higher than 82% at 623K and methanol conversion of 34%, under the operating conditions studied. The activated carbon catalytic activity and stability, under inert and oxidant atmospheres, as well as different regeneration procedures, were studied. In the absence of oxygen, the catalyst suffers a progressive deactivation by coke deposition on the active acid sites (Fig. 1). The presence of oxygen modifies the carbon surface chemistry, probably through oxygen spillover on the catalyst surface, where the availability of labile oxygen avoids catalyst deactivation. A reaction mechanism has been proposed where methanol dehydration seems to proceed through an Eley-Rideal mechanism, which assumes the adsorption of water and oxygen spillover on the acid active sites, avoiding coke deposition

Modification of the morphology, porosity and surface chemistry of lignin-based electrospun carbon materials

Lignin is a biopolymer that can be found as the main component of plants. It is obtained as a coproduct in the papermaking and biofuel industries. Owing to its high carbon and aromatic content, high availability and reduced cost, it is an excellent precursor for the preparation of highly valued carbon materials. Electrospinning is a suitable top-down technique for the preparation of polymeric fibers using high voltage electrical fields and polymer solutions of proper viscosity and conductivity. Organosolv lignins, which are extracted from lignocellulosic biomass using organic solvents, are soluble in ethanol, obtaining a solution that matches the requirement of the electrospinning process. In this way, it is possible to produce lignin-based porous carbon fibers using a coaxial electrospinning device [1]. This contribution summarizes our findings about the preparation of carbon materials with different morphologies and composition by processing lignin using electrohydrodynamic forces. Lignin spheres, beaded fibers, straight fibers, beaded tubes and straight tubes are obtained by using coaxial and triaxial spinnerets that allows the electrospinning of two or three different solutions at once [1], Fig. 1. Thermal stabilization in air is needed in order to avoid melting of lignin fibers during carbonization. Stabilization times of 48-96 hours are usually required in this step, decreasing the sustainability of the production process. Phosphoric acid can be added in small amounts in the lignin solution, shortening the time for achieve a successful thermostabilization of the fiber [2]. The carbonized materials show narrow microporosity and large surface area values (SBET from 600 to 1000 m2g-1) and additional pore size and volume can be developed by controlled gasification.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. This work was supported by the Spanish Ministry of Economy and Competitiveness and FEDER (CTQ-2015-68654-R)

Reflections about my evolution and my experience as an english teacher: how to teach and how to learn

Este proyecto es un análisis crítico y comparativo entre dos trabajos realizados a lo largo del Máster sobre lo que significa la docencia en la enseñanza de Lenguas extranjeras (en este caso inglés)y como ha evolucionado a lo largo del tiempo. Los trabajos analizados son la programación de un curso y la unidad de trabajo (o unidad didáctica)teniendo en cuenta aspectos metodológicos, objetivos, fines, etc. Contiene propuestas de futuro de mejora para la docencia y mis reflexiones como futura docente

Dibujo de líneas tridimensional sobre nubes de puntos mediante estéreo cromático y sombreado

1 PDF document (8 pp., English).-- Contributed to: VSMM'08: 14th International Conference on Virtual Systems and Multimedia (Limassol, Cyprus, Oct 20-25, 2008)[EN] Terrestrial laser scanners (TLS) have become a common tool in geometric documentation of heritage. As output, they can produce point clouds along with thematic information such as reflectance or photographic texture. Some of their drawbacks are that the products which have been directly obtained from raw point clouds imply massive data handling, besides, standard products demanded by organizations and technicians such as wireframe models and line drawings are not readily computed from them; therefore, human supervised point cloud processing is still mandatory. Our contribution is to enriching the point cloud thematic component using shading and Chromadepth® information, which allows to enhance the point cloud surface details and to improve the identification and drawing of the lines defining the elements over the point cloud. In order to illustrate the utility of these thematic layers, we describe, step by step, a simple procedure to draw 3D lines from point clouds.[ES] Los sistemas de escaneado laser se han convertido en una herramienta habitual en la documentación geométrica del patrimonio. Como uno de sus resultados, se obtienen nubes de puntos que incluyen información adicional como la reflectancia o el color procedente de una textura fotográfica. Sin embargo, su manejo implica la gestión de ficheros brutos de gran tamaño y no es sencillo obtener algunos de los productos que se demandan por los técnicos habituados al trabajo patrimonial como son los dibujos de líneas. Nuestra contribución consiste en enriquecer la componente temática mediante el sombreado y el estéreo cromático, resaltando los detalles de la superficie documentada y mejorando la identificación y dibujo de las líneas. Con el fin de ilustrar la utilización de capas temáticas para el dibujo 3D, se describe, paso a paso, un procedimiento simple para el dibujo tridimensional a partir de nubes de puntos

Activated carbons as catalytic support for Cu nanoparticles

There are a wide range of catalytic applications for Cu-based nanoparticles materials, since Cu is an abundant and inexpensive metal and Cu nanoparticles possess unusual electrical, thermal and optical properties. The possible modification of the chemical and physical properties of these nanoparticles using different synthetic strategies and conditions and/or via postsynthetic chemical treatments has been largely responsible for the rapid growth of interest in these nanomaterials and their applications in catalysis. A previous work have explored the possibilities of SBA-15 (1,2) as support for Cu nanoparticles. In the present contribution, those results will be compared with the use of a carbon material as support, since activated carbon present many advantages with respect SBA, as the high surface area.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech