Novel Porous Composite Material Containing Catalytic Nanoparticles for Hydrogen Production from Biofuel
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Novel Porous Composite Material Containing Catalytic Nanoparticles for Hydrogen Production from Biofuel Nico Hotz Thermodynamics and Sustainable Energy Lab, Department of Mechanical Engineering and Materials Science, Duke University 303 Hudson, Box 90300 Durham, NC 27708-0300, USA ABSTRACT In this study, a novel flow-based method is presented to place catalytic nanoparticles into a reactor by sol-gelation of a porous ceramic consisting of copper-based nanoparticles, silica sand, ceramic binder, and a gelation agent. This method allows for the placement of a liquid precursor containing the catalyst into the final reactor geometry without the need of impregnating or coating of a substrate with the catalytic material. The so generated foam-like porous ceramic shows properties highly appropriate for use as catalytic reactor material, e.g., reasonable pressure drop due to its porosity, high thermal and catalytic stability, and excellent catalytic behavior. The catalytic activity of micro-reactors containing this foam-like ceramic is tested in terms of their ability to convert alcoholic biofuel (e.g. methanol) to a hydrogen-rich gas mixture with low concentrations of carbon monoxide (up to 75% hydrogen content and less than 0.2% CO, for the case of methanol). This gas mixture is subsequently used in a low-temperature fuel cell, converting the hydrogen directly to electricity. A low concentration of CO is crucial to avoid poisoning of the fuel cell catalyst. Since conventional Polymer Electrolyte Membrane (PEM) fuel cells require CO concentrations far below 100 ppm and since most methods to reduce the mole fraction of CO (such as Preferential Oxidation or PROX) have CO conversions of up to 99%, the alcohol fuel reformer has to achieve initial CO mole fractions significantly below 1%. The catalyst and the porous ceramic reactor of the present study can successfully fulfill this requirement. The results of the present study confirm that product gas mixtures with up to 75% hydrogen content and less than 0.2% CO content can be achieved, which is an excellent result. The reactor temperature can be kept as low as 220°C while obtaining a methanol conversion of up to 70%. The used PROX catalyst showed selective CO conversion rates above 99.5% for temperatures between 80 and 100˚C in presence of large molar fractions of H2O and CO2. INTRODUCTION The main objective addressed in this study is the proof that a hybrid solar energy conversion system in combination with Proton Exchange Membrane (PEM) fuel cell technology can achieve advantages in terms of energetic efficiency and that this system can be operated in a costeffective manner for consumer’s benefits. This proof-of-concept is conducted in form of experiments, assisted by analytical and numerical analysis and optimization of the system. The purpose of this project is the combination of a solar-powered reformer generating hydrogen from an alcoholic biofuel, such as methanol and bio-ethanol, with a low-temperature fuel cell to achieve a hybrid solar system for stationary electric
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