Hydrolysis of cellulose to fermentable sugars by using 2,5-furandicarboxylic acid as a recyclable catalyst in green solvent of GVL/ H2O

Hydrolysis of cellulose into C 6 sugars is the starting point and entry point for biomass refining and is an important pathway for biofuel production. However, biomass-based 2,5-furandicarboxylic acid (FDCA) is a highly catalytic promising but underutilized organic carboxylic acid. In this paper, we investigated the use of easily recoverable FDCA as a catalyst for the hydrolysis of cellulose to produce C 6 sugars in a γ-valerolactone/water (GVL/H 2 O) green solvent system. FDCA has high inherent acidity (pKa = 2.76) and stability with unique solubility in aqueous solutions and many solvents. These properties allows it to meet both high temperature solubility for efficient homogeneous hydrolysis reactions and low temperature crystallization catalysts for high purity recovery. This process not only solves the problem of solid-solid mass transfer between solid acid and cellulose which limits the hydrolysis rate, but also eliminates the problem of difficult separation and recovery of liquid acid catalysts. The results showed when initial concentration of microcrystalline cellulose was 0.7 wt%（equivalent to 7 g/L）, and the initial dosage of FDCA was 2.0 wt%, the maximum yield of C 6 sugars reached 72.9% (40.1% glucose and 32.8% fructose) in GVL/H 2 O (60/40, V/V) with a reaction at 200 °C for 30 min. More importantly, FDCA can achieve 80% recovery and ＞99% spectroscopic purity recovery. This study reveals the potential of FDCA as a catalyst in the catalytic conversion of biomass, which provides a new pathway for the green and efficient conversion of biomass resources.