Examinando por Materia "CATALISIS"

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  • Tesis de maestría
    Catalytic cleaning process for high pressure electrolyzers
    (2017) Dijk, Nicolás van; Jordan, Thomas; Grune, Joachim
    "The on growing global energy demand and the increasing need to reduce greenhouse gas emissions in order to avoid the worst case scenarios of global warming, forces to introduce cleaner and more sustainable technologies and practices into all sector of the economy. Therefore, electricity produced by renewable sources is continuously increasing in the energy matrix worldwide. One drawback of the renewable energies is the generation intermittency. This issue positions hydrogen as one of the main characters to store the surplus energy and blend the uctuations by producing and storing it at high pressure. Hydrogen can be produced by splitting water using an electrolyzer. Moreover, in order to increase the power-to-gas eficiency, high pressure electrolyzer are being developed. Gas cross contamination in high pressure electrolyzers is a burden that needs to be tackled in Gas order to avoid unwanted ignition events. Therefore, a cleaning process needs to be implemented. In this master thesis a catalytic cleaning process is tested with an existent experimental set up. Tests are performed with pressures up to 90 bar and the behavior of the catalytic material is assessed. Results show v 10% efciency increase with pressure increase along the pressure range tested. It is found that pressure range is bounded due to experimental set-up limitations and modifications to the test facility are proposed."
  • Artículo de Publicación Periódica
    Synthesis and regeneration of nickel-based catalysts for hydrodeoxygenation of beech wood fast pyrolysis bio-oil
    (2018-10) Schmitt, Caroline Carriel; Gagliardi Reolon, María Belén; Zimmermann, Michael; Raffelt, Klaus; Grunwaldt, Jan-Dierk; Dhamen, Nicolaus
    "Four nickel-based catalysts are synthesized by wet impregnation and evaluated for the hydrotreatment/hydrodeoxygenation of beech wood fast-pyrolysis bio-oil. Parameters such as elemental analysis, pH value, and water content, as well as the heating value of the upgraded bio-oils are considered for the evaluation of the catalysts’ activity and catalyst reuse in cycles of hydrodeoxygenation after regeneration. The reduction temperature, selectivity and hydrogen consumption are distinct among them, although all catalysts tested produce upgraded bio-oils with reduced oxygen concentration, lower water content and higher energy density. Ni/SiO2, in particular, can remove more than 50% of the oxygen content and reduce the water content by more than 80%, with low coke and gas formation. The evaluation over four consecutive hydrotreatment reactions and catalyst regeneration shows a slightly reduced hydrodeoxygenation activity of Ni/SiO2, mainly due to deactivation caused by sintering and adsorption of poisoning substances, such as sulfur. Following the fourth catalyst reuse, the upgraded bio-oil shows 43% less oxygen in comparison to the feedstock and properties comparable to the upgraded bio-oil obtained with the fresh catalyst. Hence, nickel-based catalysts are promising for improving hardwood fast-pyrolysis bio-oil properties, especially monometallic nickel catalysts supported on silica."
  • Tesis de maestría
    Synthesis of nickel-based catalysts and their application in pyrolysis oil upgrading in a batch reactor
    (2018) Gagliardi Reolon, María Belén; Carriel Schmitt, Caroline
    "The thermochemical decomposition of beech wood biomass results in a poor quality bio-oil, which cannot be directly used in diesel engines. In order to make this oil resemble liquid fossil fuels, an upgrading technique should be applied. Among the available possibilities, hydrodeoxygenation (the removal of oxygen and saturation of double bonds through high pressure hydrogen) appears to be the most auspicious route to produce biofuels. Besides, this method requires a catalyst to increase the activity, which could be reused in further upgrading reactions so as to minimize the generation of waste material. In this work, four nickel-based catalysts were evaluated for the hydrodeoxygenation of beech wood bio-oil. After being synthesized, their superficial and compositional characteristics were assessed. Once the upgrading reaction was performed for the pyrolysis oil, the resulting products (upgraded bio-oil, aqueous phase and gas fraction) were separately analyzed. Considering the obtained results, the catalyst with the best upgrading performance was selected in order to regenerate and use it in further hydrodeoxygenation reactions. The catalyst selection was based on upgraded bio-oil, catalyst and reaction factors. Parameters such as carbon, oxygen and water content, HHV, pH value, poisoning and overall hydrogen consumption were taken into account. With the obtained results, Ni/SiO2 was chosen and therefore regenerated, which included the calcination and reduction of the spent catalyst before it was reused in a new hydrodeoxygenation reaction. Its performance was tested along three consecutive reactions and the quality of upgraded bio-oils corresponding to these cycles were evaluated. It could be concluded that Ni/SiO2 showed an improvement in the upgraded bio-oil quality next to a satisfactory performance after the three regeneration cycles, which points out that this particular catalyst can be regenerated and reused for a minimum of three times without significantly affecting the resulting upgraded bio-oil quality. Further characterization techniques should be performed in order to achieve a bigger understanding of the functioning of nickel-based catalysts and their reutilization in a larger number of consecutive upgrading reactions."