Efficient green catalysis for the conversion of fructose to levulinic acid

Abstract

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 24h in a 50:50 mixture of water/GVL resulting in 72mol% 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.