Efficient green catalysis for the conversion of fructose to levulinic acid

- Demonstration of fructose to levulinic acid with very high activity and selectivity using Dowex 50 × 8-100 resin.
- We obtained an efficient system capable to produce the transformation under benign conditions.
- This work provides more flexibility than dual catalyst systems reported previously, behaving as a switchable catalyst for LA and HMF production depending on the nature of solvent.
- Mechanistic insight provided on the formation of by-products leading to humins, the primary catalyst fouling mechanism for this reaction.

Highly efficient and selective production of levulinic acid has been achieved from D-fructose in the presence of polystyrene-based sulphonic acid resin catalyst, Dowex 50 × 8-100, at mild reaction conditions of 120 °C, over 24 h in a 50:50 mixture of water/GVL resulting in 72 mol% yield under optimized reaction conditions. Optimization of the effect of reaction temperature, time, pressure, catalyst to substrate ratio, fructose concentration and solvent was performed. Various polystyrene-based sulfonic acid resins were also investigated for quantitative production of LA from 5-hydroxymethylfurfural (5-HMF) in pure water. Catalyst recycling was carried out up to 6 cycles. Significant mechanistic information was obtained for the formation of “humins”, which are the primary cause of catalyst fouling, by the identification of soluble by-products and polymerization presursors using Q-Tof mass spectrometry based on accurate masses.

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