Transformations of biomass-based levulinate ester into γ-valerolactone and pyrrolidones using carbon nanotubes-grafted N-heterocyclic carbene ruthenium complexes

Abstract

Abstract As a renewable biomass-based compound with wide applications in food additives, fine chemical synthesis and fuels, γ-valerolactone (GVL) has attached much attention. While, pyrrolidones are widely used in pharmaceutical, agrochemical, material industrial and other chemical production. In this research, we demonstrated transformations of biomass-based ethyl levulinate (EL) into GVL and pyrrolidones by using heterogeneous catalysts (CNT-Ru-1) with N-heterocyclic carbene ruthenium (NHC-Ru) complex grafted on multi-walled carbon nanotube (CNT). The Ru catalyst showed high efficiency on EL hydrogenation to GVL with both EL conversion and GVL yield exceeding 99%. Moreover, the Ru catalyst readily promoted reductive amination of EL in the presence of various amines for pyrrolidone synthesis. Finally, the Ru catalyst was also applicable to hydrogenation of various carbonyl compounds for the synthesis of the corresponding alcohols with excellent catalytic performance. The research provides insight for heterogenizing the homogeneous noble metal-based catalysts with high catalytic active for biomass-based transformations.