Effect of ZrO2 phases in the Catalytic Transfer Hydrogenation of Methyl Levulinate: a computational and experimental study

The Levulinic Acid (LA) and its esters like Methyl Levulinate (ML) are promising bio-derived molecules and their study is a crucial step in the development of a new and greener chemical industry. Among the possible product derived from their transformation, there is the γ-Valerolactone (GVL), which is itself a platform molecule but even a promising biofuel. For several reasons, the Catalytic Transfer Hydrogenation (CTH) process is gaining more and more interest, representing a desirable route to produce GVL. The CTH is a Lewis acid-catalyzed reaction, therefore cheap materials with acid properties, such as zirconium oxide, will be optimal for the industrial implementation of the reaction. In this thesis, the CTH of ML to GVL was investigated on two crystallographic phases of ZrO2: monoclinic zirconium oxide (m-ZrO2); tetragonal zirconium oxide (t-ZrO2). The two catalysts were then tested in a gas phase continuous flow reactor in conditions previously optimized by the research group, analyzing the effect of the two phases and their interaction with different H-donor. The catalysts were also characterized by means of XRD, BET and TPD experiments. In order to have an atomistic comprehension of the different reactivity on the two ZrO2 phases, a computational study employing the Density Functional Theory (DFT) was carried out. First, a modelling of the two catalysts was accomplished to obtain stable and reliable model structures for both ZrO2 phases. Three DFT exchange -correlation functionals have been compared to optimize the computational method: PBE, PBE0 and B3LYP. Secondly, the adsorption sites of the two models were characterized, in particular analyzing the electrophilic/nucleophilic, acid, and basic nature. Finally, the adsorption of one intermediate expected to be crucial for the ML to GVL conversion (i.e., the α-Angelica Lactone) was studied computationally, providing relevant insights on the effects of the ZrO2 phase in this CTH process.