Shaping of Zr-β zeolite nanocrystals through spray drying for the upgrading of levulinates to γ-valerolactone
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- This master thesis focusses on the upgrading of levulinate esters to γ-valerolactone, a green solvent and fuel additive, using Zr-beta zeolite nanocrystals. These nanocrystals were shaped into microparticles by spray drying to overcome practical issues related to the colloidal size of the nanocrystals (handling, recovery, reuse, …). Three features of the catalyst were extensively studied during this master thesis. First, screening of Zr loadings was performed to enhance the catalytic activity. Zr-beta nanocrystals with a molar Si/Zr ratio of 26 obtained the highest productivity with 4.05 ± 0.55 mmolGVL/h.gcat. Overall, the productivity of the catalyst is among the highest reported in the literature. Second, the potential of Zr-beta microparticles obtained by spray drying of Zr-beta nanocrystals was investigated. A 78 % decrease in productivity was observed, which could be associated with the use of a binder covering the surface and blocking the pores of the catalyst, preventing subsequent impregnation of active Zr species. Third, the potential issue of internal diffusional limitations was studied to demonstrate whether the levulinate esters mostly react on the surface of the catalyst or rather in the micropores. Based on the conducted experiments and on the literature, the levulinate ester should not cause diffusion limitations in the micropores. However, the catalytic results suggested potential mass transport limitations to some extent due to the diffusion of γ-valerolactone in the micropores. In summary, this work enabled us to showcase the high catalytic activity of Zr-beta nanocrystals and to demonstrate potential issues regarding the spray drying process of nanocrystals and the diffusion of γ-valerolactone in micropores.