Synthesis and Optimization of MOF Catalyst for Biomass Valorization: Application on MOF-808 =

Methyl Levulinate is a crucial biomass platform molecule of high interest as a fuel blending additive. A newly studied reaction still under the preliminary investigation based on the formation of Methyl Levulinate starting from Ethyl Levulinate gains a great interest due to the increased product selectivity and lower activation energy, with no evidence of good performing catalyst. Over the last few years, innovative catalytic formulations based on Metal-Organic Framework have gained large interest for their unique structural topologies, high surface area, and tunable pore size. In this research project, Zr-MOF-808 has been selected as good candidate to drive the transesterification endowed by its promising catalytic properties. In literature studies, MOF-808 has been designed following different procedures and parameters, sometimes leading to poorly-ordered material. A clear indication of the relationship between the synthesis parameters and the chemical-physical properties of the final material is not reported. Since the real strength of a synthesis lies in the ability to identify the key factors boosting the performance in the selected application, this research work aimed to rigorously assess the intrinsic effects of reaction parameters on the properties of MOF-808. The best materials were then tested in a batch reactor in the formation of methyl levulinate from ethyl levulinate. MOF-808 was synthesized solvothermally followed by different optimization paths. ZrOCl2.8H2O and ZrCl4 were used as Zr sources, formic or acetic acid were used as modulators with different amounts, different reaction time were explored, and different molar ratios between zirconium precursors and organic ligand given by Zr/BTC=1:1 and Zr/BTC=3:1 were tested. All these parameters impose a direct effect on the MOF properties such as its surface area, stability, crystallite size, and the number of defects that are characterized by BET, PXRD, TGA and SEM. The results of this project can be summarized as follows: 1)Samples synthesized with formic acid show much-developed crystallinity, surface area, and defects concentration than samples synthesized with acetic acid. 2)A higher volume of the acidic modulator proves to tune the properties increasing surface area, microporosity, and crystallinity. 3)Samples synthesized with formic acid or acetic acid using different Zr/BTC molar ratio didn't show much different overall properties. 4)ZrOCl2.8H2O resulted to be the best precursors when combined with formic acid in contrast to sample synthesized with ZrCl4 which shows a drop in the properties. 5)All promising samples were obtained by a lower temperature and synthesis duration than the ones reported in literature with almost matching properties. 6) Catalyst show high structural stability in water and acid medium whereas a complete collapse in basic medium was observed. 7) Formic acid samples show an increase in the final conversion as the synthesis time decrease, with much higher conversion values than acetic acid samples 8) Higher conversion values with lower energy consumption was reached in the reaction system by MOF catalysts synthesized with formic acid with respect to acid catalysts reported in literature for the transesterification reaction.