One pot microwave-assisted catalytic upgrading of α-angelicalactone to γ-valerolactone over scandium triflate without H2 supply

Abstract

Biomass upgrading, which supplies important biomaterials, chemicals and fuels, is considered as an efficient way to realize the goal of carbon neutralization. Recently, γ-valerolactone (GVL) has gained increasing attention due to its wide applications. In this work, a novel protocol of microwave-assisted cascade catalytic upgrading of α-angelicalactone (α-AL) to GVL over metal triflate using alcohol as the hydrogen donor was proposed. The yield of GVL production from α-AL upgrading is strongly influenced by the Lewis acid strength of the metal triflate and the reduction potential of the employed alcohol. Among all tests, Sc(OTf)3 showed the best catalytic performance in isopropanol media, giving 96.4 % GVL yield and 100 % α-AL conversion at 433 K within 3.0 h. Meanwhile, kinetic study indicated transfer hydrogenation of isopropyl levulinate to isopropyl 4-hydroxyvalerate was the rate-limited step with the apparent activation energy of 94.5 kJ/mol. This Sc(OTf)3 catalyst was highly stable and could be reused for five cycles by simple vacuum distillation. In a word, this work provides an alternative for GVL production from biomass upgrading.