Hydrogenation of levoglucosenone to renewable chemicals

Abstract

We have studied the hydrogenation of levoglucosenone (LGO) to dihydrolevoglucosenone (Cyrene), levoglucosanol (Lgol), and tetrahydrofurandimethanol (THFDM) and elucidated the reaction network over supported palladium catalysts. At low temperature (40 °C) over a Pd/Al₂O₃ catalyst, LGO is selectively hydrogenated to Cyrene. At intermediate temperatures (100 °C) over a Pd/Al₂O₃ catalyst, Cyrene is selectively hydrogenated to Lgol, with an excess of the exo-Lgol isomer produced over the endo-Lgol isomer. At higher temperatures (150 °C) over a bifunctional Pd/SiO₂–Al₂O₃ catalyst, Lgol is converted to THFDM in 58% selectivity, with 78% overall selectivity to 1,6-hexanediol precursors. The ratio of cis-THFDM relative to trans-THFDM is approximately 2.5, and this ratio is independent of the Lgol feed stereoisomer ratio. Tetrahydropyran-2-methanol-5-ketone (THP2M5one) and tetrahydropyran-2-methanol-5-hydroxyl (THP2M5H) are side-products of Lgol hydrogenolysis, but neither of these species are precursors to THFDM.