Publications (5)0 Total impact
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Article: Analytical pyrolysis as a characterization technique for monitoring the production of carbon nanofilaments
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ABSTRACT: The main step in the production of carbon nanofilaments is the catalytic nucleation and lengthening of the filament. An undesired parallel step in the production of carbon nanofilaments is their thickening by pyrolitic carbon vapor deposition consisting in an ordered polycondensation of carbon over an existing catalytic carbon nanofilament. The regular characterization of the structure of carbon nanofilaments (coated or not) is by transmission electron microscopy. However, this technique is not affordable in many cases because is expensive and complex. In the present work, the analytical pyrolysis is proposed to obtain clues of the structure of carbon nanofilaments. Several commercial carbon nanofilaments have been analyzed. The samples with a thicker soot layer evolve a higher amount of heavy PAHs in the pyrolysis runs than the ones free of soot. It has been observed that pyrene is a key compound in the pyrolytic carbon vapor deposition process and the resulting formation of soot over the carbon nanofilaments. The aim of this work is to get useful information about the quality of the carbon filaments by a cheap technique, the analytical pyrolysis. -
Article: Thermogravimetric analysis during the decomposition of cotton fabrics in an inert and air environment
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ABSTRACT: The thermal degradation of samples of used cotton fabrics has been investigated using thermogravimetric analysis (TGA) between room temperature and 700 °C. Experiments were carried out with about 5 mg of sample in three different atmospheres: helium, 20% oxygen in helium and 10% oxygen in helium. Three different heating rates were used at each atmosphere condition. A kinetic model for the decomposition of used cotton fabrics explaining the behavior of all the runs performed has been proposed and tested. For the pyrolysis of the cotton, the model comprises two parallel reactions. For the combustion process, one competitive reaction was added to each parallel reaction of the pyrolysis model and four combustion reactions of the different solid fractions to obtain volatiles. One single set of parameters can explain all the experiments (pyrolysis, oxidative pyrolysis and combustion) at the three different heating rates used. Support for this work was provided by the Ministerio de Educación y Ciencia of Spain, research projects PPQ2002-00567 and PPQ2002-10548-E. -
Article: Semivolatile and volatile compounds from the pyrolysis and combustion of polyvinyl chloride
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ABSTRACT: Emissions evolved from the pyrolysis and combustion of polyvinyl chloride (PVC) were studied at four different temperatures (500, 700, 850 and 1000 °C) in a horizontal laboratory tubular quartz reactor in order to analyse the influence of both temperature and reaction atmosphere on the final products from thermal and oxidative reactions. It was observed that the CO2/CO ratio increased with temperature. Methane was the only light hydrocarbon whose yield increased with temperature up to 1000 °C. Benzene was rather stable at high temperatures, but in general, combustion at temperatures above 500 °C was enough to destroy light hydrocarbons. Semivolatile hydrocarbons were collected in XAD-2 resin and more than 160 compounds were detected. Trends on polyaromatic hydrocarbon (PAH) yields showed that most had a maximum at 850 °C in pyrolysis, but naphthalene at 700 °C. Formation of chlorinated aromatics was detected. A detailed analysis of all isomers of chlorobenzenes and chlorophenols was performed. Both of them reached higher total yields in combustion runs, the first ones having a maximum at 700 °C and the latter at 500 °C. Pyrolysis and combustion runs at 850 °C were conducted to study the formation of polychlorodibenzo- p-dioxins (PCDDs) and polychlorodibenzofurans (PCDFs). There was more than 20-fold increase in total yields from pyrolysis to combustion, and PCDF yields represented in each case about 10 times PCDD yields. Support for this work was provided by Ministerio de Educación y Ciencia of Spain and research projects PPQ2002-00567 and PPQ2002-10548-E. -
Article: Emission of PCDD/Fs from combustion of pine needles and pine cones in a residential stove
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ABSTRACT: Comunicación presentada en el 27th International Symposium on Halogenated Persistent Organic Pollutants – DIOXIN 2007, Tokyo, September 2-7, 2007 Combustion of pine needles and pine cones in a residential stove was performed to assess potential emissions of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) from house fires and forest fires. In order to know the level of pollutants in the samples themselves, analyses of PCDD/Fs in the materials used were made. The PCDD/F content found in pine needles was 0.66 ng I-TEQ/kg, while for pine cones a lower value of 0.33 ng I-TEQ/kg was obtained. In the combustion experiment a high value of dioxins and furans was obtained, 196 ng I-TEQ/kg material burnt. The homologue profiles of PCDD/Fs showed differences between the materials and the flue gas emissions. The results obtained show that this kind of uncontrolled combustion is an important source of dioxins and furans. Support for this work was provided by Generalitat Valenciana -Spain. Group 03/090. -
Article: Reactores heterogéneos / J.A. Conesa Ferrer, R. Font Montesinos.
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ABSTRACT: Libro de ingeniería de reactores. Contenido: Introducción; Ecuación de velocidad; Ecuación de velocidad para las etapas químicas como etapas limitantes (mecanismos de catálisis; teorías de adsorción); Ecuación de velocidad para la difusión externa como etapa limitante; Tipos de difusión interna; Velocidad de reacción cuando la difusión interna es lenta; Efecto de la temperatura en la velocidad de reacción; Tipos de reacciones; Diseño de reactores de lecho fijo con relleno.
