Proceso para la obtención de tamices moleculares de carbón

La presente invención describe un proceso en el que un precursor de carbón adecuado, como por ejemplo fibras de carbón, fibras de carbón activadas, carbones activos etc. se someten a un calentamiento en un horno microondas en condiciones de temperaturas elevadas y atmósfera inerte. Las particulares características de este calentamiento en microondas producen cambios en la textura porosa de los precursores en forma tal que los transforma en materiales que pueden ser denominados tamices moleculares de carbón. Los tamices moleculares así obtenidos presentan una selectividad para la separación de mezclas O2/N2, CO2/CH4, comparable a la de otros tamices moleculares de carbón obtenidos mediante otros métodos más complejos y costosos que el aquí descrito.Peer reviewe

New acrylic monolithic carbon molecular sieves for O2/N2 and CO2/CH4 separations

8 pages, 5 figures, 4 tables.-- Available online Dec 20, 2005.The modification of activated carbon fibres prepared from a commercial textile acrylic fibre into materials with monolithic shape using phenolic resin as binder was studied. The molecular sieving properties for the gas separations CO2/CH4 and O2/N2 were evaluated from the gas uptake volume and selectivity at 100 s contact time taken from the kinetic adsorption curves of the individual gases. The pseudo-first order rate constant was also determined by the application of the LDF model. The samples produced show high CO2 and O2 rates of adsorption, in the range 3–35 × 10−3 s−1, and in most cases null or very low adsorption of CH4 and N2 which make them very promising samples to use in PSA systems, or similar. Although the selectivity was very high, the adsorption capacity was low in certain cases. However, the gas uptake in two samples reached 23 cm3 g−1 for CO2 and 5 cm3 g−1 for O2, which can be considered very good. The materials were heat-treated using a microwave furnace, which is a novel and more economic method, when compared with conventional furnaces, to improve the molecular sieves properties.The authors are grateful to the Fundação para a Ciência e a Tecnologia (Portugal), the European Regional Development Fund (FEDER) and Scientific and Technological Cooperation Program GRICES/CSIC (2004/5_4.1.1) for financial support.Peer reviewe

Conventional and microwave induced pyrolysis of coffee hulls for the production of a hydrogen rich fuel gas

8 pages, 1 figure, 5 tables. -- Available online 12 September 2006. -- Issue title: PYROLYSIS 2006: Papers presented at the 17th International Symposium on Analytical and Applied Pyrolysis (Budapest, Hungary, 22-26 May 2006)This paper describes the conventional and microwave-assisted pyrolysis of coffee hulls at 500, 800 and 1000 °C. The influence of the pyrolysis method and temperature on the product yields and on the characteristics of the pyrolysis products is discussed. It was found that the pyrolysis of this particular residue gives rise to a larger yield of the gas fraction compared to the other fractions, even at relatively low temperatures. A comparison of microwave-assisted pyrolysis and conventional pyrolysis showed that microwave treatment produces more gas and less oil than conventional pyrolysis. In addition, the gas from the microwave has much higher H2 and syngas (H2 + CO) contents (up to 40 and 72 vol.%, respectively) than those obtained by conventional pyrolysis (up to 30 and 53 vol.%, respectively), in an electric furnace, at similar temperatures. From the pyrolysis fraction yields and their higher heating values it was found that the energy distribution in the pyrolysis products decreases as follows: gas > solid > oil. Moreover, the energy accumulated in the gas increases with the pyrolysis temperature. By contrast, the energy accumulated in the char decreases with the temperature. This effect is enhanced when microwave pyrolysis is used.Peer reviewe

Changes in the exploitation dynamics of small terrestrial vertebrates and fish during the Pleistocene-Holocene transition in the SW Iberian Peninsula: A review

The Pleistocene-Holocene transition c. 11.5 ka cal. BP is associated with dramatic climatic changes. These events led to fundamental shifts in landscape and have, therefore, been seen as responsible for a major impact on the human ecological behavior of the last hunter-gatherers in the Western European territory. In the case of Iberian Peninsula, it is commonly assumed that these human ecological adaptations are reflected in the new settlement and subsistence patterns that characterized the Late Upper Paleolithic-Mesolithic transition. Following the argument, the main aim of this paper is to present the state-of-the-art and consider this theoretical model using zooarchaeological data of small terrestrial vertebrates and fish from SW Portugal. Archaeological data are reviewed and discussed in order to analyze the change in the exploitation of small game, birds, and aquatic resources during this period. In this paper, we reinforce the idea that in SW Iberia, subsistence intensification and diversification precede the transition itself and are more likely to be related to other long-term phenomena, cultural and/or demographical, than to the changes in settlement behavior. The state-of-the-art discussed here led to new research questions related to the role of small vertebrates on the changes in human subsistence behavior during the Pleistocene-Holocene from Western Iberia