Clean Synthesis of 5-Hydroxymethylfurfural and Levulinic Acid by Aqueous Phase Conversion of Levoglucosenone over Solid Acid Catalysts

Levoglucosenone (LGO) is an emerging bio-renewable platform for the fine and commodity chemical industries. Herein, we report an aqueous phase conversion of LGO to 5-hydroxylmethylfurfural (HMF) and levulinic acid (LA) over solid acid catalyst. Several types of solid acid catalysts such as zeolites, strongly acidic ion-exchange resin, and sulfonated activated carbon were investigated for this reaction. Among the tested catalysts, ZSM-5 and Amberlyst 70 showed the best performances for selectively producing the target products, resulting in the highest total yield of HMF and LA at 72.2% on a molar basis. Factors decreasing the reaction selectivity were identified through the comparison of catalysts and kinetic analysis to the pore morphology, presence of Lewis acid sites, and formation of degradation products directly from LGO or its hydrated product. ZSM-5 and Amberlyst 70, after a single-batch experiment, contained deposits from the degradation products but could be reused with little loss in activity, although calcination was required for ZSM-5. The catalytic system, employing LGO as feedstock and recyclable solid acid catalysts, uses only water as reaction media and thus has the potential to be a clean route for producing the key building blocks HMF and LA.