Catalytic transfer hydrogenation of bio-based feedstocks to valuable chemicals and fuels

Abstract

Biomass-derived chemicals are gaining interest as sustainable alternatives to fossil-based resources. Ethyl levulinate (EL) and γ-valerolactone (GVL) are especially promising, EL is used in bio-lubricants, resins, plasticisers, and food flavourings, while GVL serves as a green solvent, fuel additive, and precursor to renewable fuels and polymers. Traditional hydrogenation relies on precious metals and high-pressure hydrogen. This study explores a scalable process using liquid hydrogen donors and earth-abundant heterogeneous catalysts for the catalytic transfer hydrogenation (CTH) of levulinic acid (LA) to GVL.

Esterification of LA to EL was investigated using sulphated and tungstated zirconia and stannia catalysts. Sulphated zirconia gave the best performance (7.6 mmolEL gcat−1 h−1), comparable to Y-zeolite (11.1 mmolEL gcat−1 h−1). For CTH reactions, a silica–zirconia catalytic system was developed, where tuning the Si content modulated surface area, crystallinity, and the Brønsted/Lewis acid ratio, promoting alternative catalytic routes for GVL formation. The 3.2 wt.% Si/ZrO2 catalyst was optimal for EL, achieving 78% conversion and 67% GVL yield due to the synergy between Lewis and Brønsted acid sites. For LA, the 6.1 wt.% Si/ZrO2 catalyst showed the highest activity with 91% conversion and 75% GVL yield, though elevated Brønsted acidity promoted esterification pathways.

The optimised Si/ZrO2 catalyst exhibited exceptional activity and stability under air, water-rich, and low-pressure conditions, demonstrating industrial robustness. Integration of esterification and transfer hydrogenation into a single one-pot process using a bifunctional 0.7 wt.% S/ Si/ZrO2–C catalyst achieved complete LA conversion, 97% GVL yield, and a productivity of 8.1 mmolGVL gcat−1 h−1, surpassing many precious-metal systems. This efficient, low-cost, and scalable process eliminates external hydrogen and harsh conditions, offering a highly viable and competitive route for large-scale GVL production from biomass-derived feedstocks.

Date of Award	Jun 2025
Original language	English
Awarding Institution	Aston University
Supervisor	Marta Granollers Mesa (Supervisor) & Stephen David Worrall (Supervisor)