Zirconia-based catalytic systems for the valorisation of biomass in chemical products of high industrial interest: an experimental and computational study

Zirconia is a particularly promising material as heterogeneous catalyst: in fact, thanks to its innumerable properties, it can be used for a large number of reactions, both as an actual catalyst and as a support for nanoparticles. In this thesis work various reactions for the valorisation of biomass were studied using zirconia-based catalysts in the gas phase and liquid phase. The hydrogenation reaction of methyl levulinate (ML) in continuous gas phase by CTH mechanism was studied, using alcohols such as H-donor. For this reaction, the two crystalline phases of zirconia were compared, the tetragonal (t-ZrO2) and the monoclinic (m-ZrO2): these were synthesized and subsequently characterized. From the catalytic tests carried out, t-ZrO2 resulted to be more active in the reaction in question and more selective towards the formation of GVL (yield of 63%). m-ZrO2, however, was found to deactivate more quickly. Material characterizations combined with computational and NMR spectroscopy studies have made it possible to explain the reasons for a faster deactivation of the monoclinic phase compared to the tetragonal one. Other zirconia-based materials with higher surface areas, compared to crystalline zirconia, have been subsequently tested, with the aim of pushing the reaction further towards consecutive products, such as Pentenoates, products interested in obtaining Pentanoates. Catalysts based on metal nanoparticles of Au and Pd (both mono and bimetallic) supported on commercial zirconia were synthesized using the sol-immobilization technique. These have been tested for the liquid phase hydrogenation of furfural by CTH mechanism using isopropanol as H-donor and the oxidation reaction of HMF in the liquid phase. Finally, the oxidation reaction of glucose to glucaric acid was studied computationally, modelling some gold clusters of 55 atoms and studying on them the adsorption of some target molecules for the reaction, to obtain interesting information on deactivation phenomena during the reaction in question.