Boletín GEC 27

ABSTRACT: Photodegradation of methylene blue (MB) on TiO2 in presence of activated carbons (AC) was studied. Two different lamps were employed and results were compared against those obtained on a commercial TiO2. Apparent first order rate constant for the degradation of MB was higher in presence of any AC in comparison of TiO2 alone but much higher under visible light irradiation. It can be concluded that TiO2 enhances its photoactivity by a factor up to 8.7 in the degradation of MB in presence of AC and this increase was associated with the surface properties of AC.

RESUMEN: El objetivo de este trabajo fue analizar el papel que desempeña el carbón activado en el proceso de ozonización del anión cianuro. Los resultados obtenidos muestran que el carbón activado previamente tratado con amoniaco incrementó considerablemente la velocidad de eliminación del anión cianuro. Los resultados obtenidos mediante FTIR y XPS muestran un incremento en la concentración de grupos carbonilo, los cuales con la interacción con el ozono podrían potenciar la generación de radicales altamente oxidantes en el medio justificándose así los resultados obtenidos.

pp. 10-13

C. Cunalata, C. Inga, G. Alvarez, C. Recalde, M. Echeverría

RESUMEN: En la determinación del contenido de carbono orgánico total presente en el suelo y la biomasa (cobertura vegetal) de los páramos de las comunidades de Chimborazo, con 210ha de páramo cuya ubicación es 746667UTM-9825400UTM, y Shobol Llinllín, con 350 ha de páramo, 754680UTM–9854678UTM, pertenecientes a San Juan en Ecuador, se seleccionaron 9 puntos de muestreo de acuerdo a la variación, características y altitud del suelo, repartidos para este estudio en tres pisos altitudinales comprendidos, para el páramo de la comunidad Chimborazo, entre 3600-3900 msnm y, en el caso de Shobol Llinllín, entre 3600-3950 msnm.

ABSTRACT: The overall combustion behaviour for coals of different rank was experimentally and numerically studied in air and oxy-fuel conditions in an entrained flow reactor. High CO2 concentrations seemed to affect volatile yield and nitrogen distribution, and also the subsequent char reactivity. To obtain similar or better ignition and combustion properties under oxy-firing conditions to those attained in air, the oxygen concentration in the CO2 and H2O(v) mixture must be about 30%. During oxy-fuel combustion, lower NO emissions were produced in comparison with air-firing conditions, although an increase on fuel-N conversion to NO was observed when increasing the oxygen concentration. The experimental findings related to coal burnout and NO emissions were used to test the accuracy of the CFD model developed for oxy-coal combustion. The CFD model predicted accurately oxy-coal combustion in the entrained flow reactor, and it was a useful tool for describing the differences in temperature, species concentration and burning profiles, during the combustion of different coals in both air an oxy-firing conditions.

ABSTRACT: The properties of CNC as well as their surface chemistry can be tuned by an adequate choice of synthesis conditions, favouring the formation of surface oxygen groups. Platinum-based catalysts have been supported on CNCs through different synthesis methods and their catalytic activity has been proven. These results prove that CNCs are promising candidates as alternative to replace Vulcan in order to improve the performance of the direct alcohol fuel cells. In addition, it can be affirmed that the reactivity of Au-Pd core-shell nanostructures toward CO and HCOOH electro-oxidation is not only determined by the composition and structure of Pd overlayer but also by interaction with the support.

ABSTRACT: A novel methodology has been developed for the direct incorporation of metallic nanoparticles inside mesoporous matrices, which we have named “simultaneous synthesis”. The prepared catalysts have shown excellent activity and selectivity in a selective hydrogenation reaction (phenylacetylene semihydrogenation). Catalysts prepared following the simultaneous synthesis protocol showed the highest activity values (expressed as TOF) for all the analyzed samples, which clearly reveals the importance of not only the support, but also the catalyst preparation method.