Development of heterogeneous catalysts for fuel and chemicals production

Substitution of a fossil sources-based society to renewable one is the main challenge of 21 century. This Ph.D. work is focused on the development of heterogeneous catalysts for biomass valorisation, concerning both fuel and chemical production. Thanks to their promising properties, H2 and Levulinic acid (LA) were selected. The common denominator of this thesis is the study and the optimization of the most suitable catalyst for each process. The ideal catalyst for H2 production must be robust and resistant to coke deposition, for this reason, optimisation of nickel-ceria and nickel-zirconia based catalyst was performed. In the case of LA, the best catalyst must be sufficiently acid to direct the conversion of glucose to the main product and suppress unwanted reactions. In this case, SBA-15, a silica mesoporous material, was properly modified introducing acid functionalities via grafting approach and by the addition of a promoter. Considering H2 production, it was demonstrated how support synthesis strongly influences the catalyst features and consequently, the catalytic activity. For ceria support, it was determined how the precipitation method allows obtaining a good catalyst with high surface area, a high degree of crystallinity and with a wide distribution of active phase. Moreover, these properties were successfully implemented introducing a promoter as lanthanum. It was found that lanthanum increases the redox ability of the Ni-ceria catalyst, guaranteeing higher stability in ESR conditions. Moreover, these properties were widely enhanced when the lanthanum was added by co-precipitation. The effect of lanthanum was also investigated in nickel zirconia-based catalyst. In this case, its influence is completely different from the ceria case. Indeed, for zirconia, lanthanum properly modulates the acidic/basic features. Moreover, in this case, the best result was obtained with the catalyst prepared via the impregnation of the promoter on the support. Thanks to this study, it was possible to enormously implement the properties of the individual support, tuning its preparation method and introducing a promoter. Considering LA production via hydrolysis, implementation of SBA-15 acidity was achieved with the introduction of aluminium and sulfonic groups. It was found a new environmentally friendly and cost-effective method to graft sulfonic acid groups over silica surface and increase its Brønsted acidity. To implement the Lewis one, it was demonstrated that the addition of alumina via evaporation-impregnation increases the number of medium and strong Lewis sites preserving the SBA-15 morphological features. Therefore, this new material has promising properties to be used in converting more complex carbohydrate substrates.