Mesoporous materials for hydrogen purification and production technologies

Resumen

The current increasing in energy demand in the world is unsustainable if it is based solely on fossil fuels. With this aim, and taking into account the current legislative environment, a change of the fossil fuels as the main energy vector perspective is required. Hence, the substitution of fossil fuels by hydrogen as an energy carrier means an important step forward to make sustainable development a reality. Nowadays there are many technologies in development related to hydrogen generation, storage, purification and use for power generation. The ideal way to produce hydrogen is to couple renewable energies with water electrolysis systems, store and use it in fuel cells to convert the stored energy in the hydrogen eficiently into power and heat. Progressively, the implementation of fuel cells with current technologies is becoming a reality. However, fossil fuels are still the hydrogen source used. To obtain high purity hydrogen for use in low temperature fuel cells, it must be free of pollutants i.e. carbon monoxide or hydrogen sulfide. Catalytic processes are currently being used to reach these objectives. To this first requirement, many processes can be used to eliminate the carbon monoxide from hydrogen-rich streams, but the CO Preferential Oxidation (CO-PROX) is one of the most promising process. In this Thesis, catalysts based in mesoporous silica SBA-15 doped with Zr as support, using the catalytic couples of CuOx/CeO2 and Au/CeO2 as the active phase, were studied. Another requirement is to eliminate the H2S from the hydrogen stream, which is also involved during the refining processes. The H2S must be removed in order to avoid catalysts poisoning and meets the emission restrictions in fuels. The current process used for H2S abatement is the Claus process, which requires complementary processes to increase the recuperation of sulfur. One of these processes is the partial oxidation of H2S, where transition metal catalysts are currently being used. In this work, novel catalysts for H2S oxidation based on mesoporous silica SBA-15 doped with Fe, were studied. In the last part, a new process to generate on-board hydrogen for transport applications is proposed. This process involves hydrogen generation via partial dehydrogenation of kerosene JET-A1 to obtain high purity CO-free hydrogen as feed for fuel cell based powerm systems. Influence of the support, treatments and addition of promoters were studied for the catalytic system Pt-Sn supported on high surface aluminas.