Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Hydrogen Production From Ethanol Over Silica Supported Cu and Zn Oxide Catalysts(Izmir Institute of Technology, 2006) Tezel, Habibe Işıl; İnal, Fikret; İnal, Fikret; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe majority of current energy needs are supplied by combustion of nonrenewable energy sources such as fossil fuels, which is associated with release of large quantities of greenhouse gases, especially carbon dioxide and other harmful emissions to the atmosphere. The gradual depletion of these fossil fuels reserves and efforts to combat pollution and greenhouse gas emissions have generated a considerable interest in using alternative sources of energy. Ethanol used in the hydrogen production process by steam reforming. The purpose of this work was to design a high performance catalyst for the production of hydrogen from steam reforming of ethanol. Ethanol steam reforming reaction is an endothermic reaction of ethanol with water to produce hydrogen and carbon dioxide. The different ZnO loading supported SiO2 catalyst and Cu promoted ZnO/SiO2 catalysts were prepared single step sol-gel method with different Cu loading. All catalysts were characterized by X-ray diffraction, BET surface area measurements and pore diameter analysis. BET surface area decreased and average pore diameter increased as the ZnO loading increased. Based on the XRD findings, it seems that zinc silicate crystallite phase is not formed under the preparation conditions used in this dissertation. The activity and selectivity tests of all catalysts were performed in a packed bed reactor with reaction temperature between 300 and 500oC. The performances of ZnO/SiO2 catalysts in ethanol steam reforming reaction were investigated as a function of ZnO loading. Cu catalysts are known as active catalysts for ethanol dehydrogenation. As the temperature was increased, the conversion increased and reached a maximum at 500oC for all Cu loadings.Master Thesis Performance Assessment of Proton Exchange Membrane Fuel Cell (pemfc) Stack by Means of Semi-Empirical Model(Izmir Institute of Technology, 2011) Kalender, Eda; Özerdem, Barış; Özerdem, Mehmet Barış; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe charge transfer coefficient estimated around 0.4In this study, the performance of a 10 kW peak power proton exchange membrane fuel cell stack under different operating conditions was investigated experimentally by its i-V polarization curve. The stack has been fed with pure hydrogen and air and PEM fuel cell stack has active area 200 cm2 and is composed of 75 single cells. The stack was tested for different reactant inlet temperatures as from 50 °C to 65 °C with 5 °C intervals keeping constant other conditions and for different relative humidities as 75%, 85% and 95% again keeping constant other operation conditions. Then the analytical nonlinear model adapted to describe the polarization curve has been discussed. Model parameters have been simultaneously estimated by fitting data into model by using LABFIT nonlinear regression program. These parameters are the cathode exchange current density, charge transfer coefficient and polymer electrolyte membrane internal resistance. The polarization curve of the fuel cell stack showed the stack performance improved from 50 °C to 65 °C temperature with the decrease of voltage losses. However the decrease of relative humidity from 95% to 75% did not show any explicit effect onto stack performance. Data fitting was obtained with reasonable model parameters in accordance with literature and with high coefficient of determination (R2) values. The effect of temperature on model parameters was also investigated. The cathode exchange current density value increased from 2.247X10-6 A/cm2 at T=50 °C to 5.643X10-6 A/cm2 at T=65 °C. The charge transfer coefficient estimated around 0.4 coherently with literature. The membrane internal resistance value followed the slightly decreasing tendency with increasing temperature as the value around 0.1 cm2.