"Hydrogen production by ethanol steam reforming over a NiAl2O4 spinel derived catalyst"

In this work the reaction of steam reforming of ethanol to produce hydrogen using a NiAl2O4 spinel catalyst has been studied, focusing in particular on how temperature, steam to ethanol ratio and space time influence the reaction. The first part of the thesis focuses on the literature related to the reaction, using different types of catalyst, while the second refers to the experimental study using a NiAl2O4 spinel derived catalyst. This study is inserted in a bigger field, that of sustainability and searching for new energy sources that do not derive from fossil fuels. Finding alternative and renewable energy sources is an issue that is becoming more and more important nowadays, both for environmental issues linked to the global warming, but also to replace fossil fuels that are no renewable sources and their quantity is rapidly decreasing. The production of hydrogen from the steam reforming of ethanol (SRE) using bioethanol would be a good solution. The steam reforming of ethanol over a NiAl2O4 spinel catalyst was analyzes in a fluidized bed reactor under a wide range of operating conditions (450-650 °C, space time up to 0.2 gcatalyst/(gEtOH/h), and steam/ethanol (S/E) molar ratio in the feed between 3 and 9) in order to select optimum conditions for maximizing H2 production. The significance that the individual reactions in the reaction mechanism have on products distribution and the role of the catalyst in the extent of these reactions have also been analyzed. For the analysis, ethanol conversion and the yield of hydrogen and carbonaceous products were calculated. It has been showed that increasing the temperature of the process favors both ethanol conversion and hydrogen yield until 600 °C, while for higher temperature the results are worst. In order to have a proper rate of reaction a space time of 0.025 gcatalyst/(gEtOH/h) is needed and in thermodynamic regime an increase in water quantity leads to better performance. Moreover, coke deposition on the catalyst was analyzed, focusing on the type of coke produced and how it is formed. The quantity of coke deposited on the catalyst decreases with temperature and S/E molar ratio and is relatively low for low value of space time. In particular, the importance of ethylene decomposition reaction as the main source of carbon deposition has been showed, that however does not lead to a strong deactivation of the catalyst. In fact, it has been found out that ethylene is an important precursor for the formation of carbon nanotubes, that doesn’t lead to complete catalyst deactivation and can be an interesting product for the market.