Siliceous and non-siliceous mesostructured iron oxide nanocomposites for H2S removal from syngas

This thesis is devoted to give a contribution to develop new mesostructured iron oxide-nanocomposites for sulphur compounds removal in view of possible applications in syngas purification from coal at mid-temperature. Even if coal is considered one of the main source of carbon dioxide production, the combination of gasification technologies with Carbon Capture and Sequestration (CCS) could in principle solve this main drawback and make coal still an appealing feedstock for hydrogen, energy, liquid fuels, fertilizers and chemicals production. In this framework, the key challenge is the effective purification of the sour syngas, which is usually carried out at low temperatures (around 50°C), leading to losses in the energy efficiency of the plant. Technologies to clean at temperatures between 300 °C and 600 °C (mid-temperature range) have been investigated in order to sort this issue out. Mesostructured metal oxide-based nanocomposites, can be proposed as potential removers in this specific range of temperatures due to their promising features and thermal stability. They consist of a mesostructured inert support able to disperse homogeneously the active phase and iron oxide chosen as active phase due to their fast kinetics and favourable thermodynamics of the reaction with H2S, as well as for their low cost and no toxicity. The use of an inorganic mesostructured materials with different textural properties (surface area, pore size and pore structure) and chemical nature (amorphous silica or crystalline titania) as a host for iron oxide nanoparticles can provide an effective way to tailor their features in terms of phase, size and size distribution and to control its dispersion. The correlation between the textural and structural properties of the nanocomposites with their performances has allowed to get new insights for the development of novel more and more efficient H2S sorbents.