Versatile Nickel–Lanthanum(III) Catalyst for Direct Conversion of Cellulose to Glycols

Abstract

Using cellulosic biomass to synthesize bulk quantities of high-value chemicals is of great interest for developing a sustainable biobased society. Especially, direct catalytic conversion of cellulose to glycols, important building blocks for polymers, remains a grand challenge. Herein, we report the development of a versatile binary nickel–lanthanum(III) catalyst for the conversion of cellulose to both ethylene glycol (EG) and propylene glycol (1,2-PG) in a yield of 63.7%, which is one of the best performances reported for this catalytic reaction. Especially, lanthanum(III) exhibited a high level of activity toward the degradation of cellulose (TON = 339) at a very low concentration (0.2 mmol/L). On the basis of density functional theory calculations and experimental analyses, we addressed a dual route for this catalytic mechanism: a major route involving the selective cracking of sugars into C2 molecules and a minor route involving the hydrogenolysis of sugar alcohols. Lanthanum(III) catalyzes the cleavage of the C2–C3 bond in glucose via sequential epimerization and 2,3-hydride shift reactions to form glycolaldehyde, the precursor of EG.