Microwave-enhanced catalytic transfer hydrogenation of levulinic acid to γ-valerolactone using zirconium-based metal organic frameworks: A comparative study with conventional heating processes

Abstract

Abstract Catalytic transfer hydrogenation (CTH) of levulinic acid (LA) to a versatile platform chemical, γ-valerolactone (GVL), has received increasing attention because CTH can be implemented using alcohols as H-donors and non-noble metal catalysts. While conventional heating is commonly used for LA conversion via CTH, microwave irradiation (MWI) is employed for the first time to converting LA to GVL via CTH using UiO-66 as a non-noble metal catalyst. In comparison with the conventional heating, the MWI significantly accelerates LA conversion to GVL as the yields and selectivities are much higher than those obtained by conventional heating. This enhancement may be because Zr-O cluster of UiO-66 is more catalytic active owing to the quick and intensive heat and promoting effects from the ligand of UiO-66 under MWI. Additionally, the MWI is still able to enhance LA conversion substantially in less suitable alcohols for LA and enable the unfavorable UiO-66-NH2 to work and making the effective catalyst, such as UiO-66-SO3H, even more catalytically active. These features indicate that MWI is certainly a useful and effective approach for enhancing LA conversion via CTH. The findings of this study are also an important basis for developing highly effective LA conversion via CTH with MWI.