Synthesis, characterization and catalytic evaluation of MOF UiO-66 in the esterification of levulinic acid

Abstract

The study of the metal-organic frameworks MOFs has experienced rapid growth over the last two decades due to their interesting properties: flexibility of design and functionalization of their pores, high specific surface area and less complex synthesis. Within this large family of materials, those containing Zr as active metal, surrounded by terephthalic acid ligands (UiO-66) are good catalysts and stable for the esterification of levulinic acid with ethanol, activities comparable to other catalysts directly. The objective of this work was synthesized compounds of the MOF UIO-66 type with zirconium as a metal precursor and zirconium tetrachloride as a metallic source, using an alternative route of synthesis, with more favorable conditions from the economic and environmental point of view.
That is why the use of alternative solvents is proposed. The synthesis was carried out using the solvotermal method at 120 °C for 24 hours. Dimethylformamide was considered as solvent and between 0 and 75% of said solvent was replaced by acetone. These materials were then catalytically evaluated in the esterification reaction of levulinic acid with ethanol. The properties of the material were characterized by X-ray diffraction, scanning electron microscopy, infrared spectroscopy, X-ray photoelectronic spectroscopy, microwave plasma atomic emission spectroscopy and superfical area. The progress of the reaction was followed by gas chromatography and mass spectroscopy. The most active material was MOF100% with 17,42% conversion and 27,17% selectivity to ethyl levulinate