High-yield synthesis of 2,5-Furandicarboxylic acid from fructose via a two-step strategy without 5-Hydroxymethylfurfural isolation using dioxane as a bridging solvent

Abstract

2,5-Furandicarboxylic acid (FDCA) is a crucial bio-platform molecule for renewable polymers and fine chemicals. Here, a two-step method including fructose dehydration and 5-hydroxymethylfurfural (HMF) oxidation has been reported as an effective strategy to produce FDCA with high yield from fructose directly. In this method, for fructose dehydration over CH3SO3H, tetramethylammonium chloride (TmaCl) was first used as phase modifier and co-solvent in a H2O-dioxane biphasic-solvent system, affording HMF yield up to 90.6 % under mild condition (383 K) with relatively high fructose concentration (e.g. 5–10 wt %). Detailed 13C NMR studies verified the interaction between TmaCl and fructose, which significantly promoted the proportion of fructofuranoses and helped to improve the fructose dehydration activity and HMF yield. After dehydration step, more than 97.8 % of CH3SO3H were recovered in reaction phase for catalyst reuse, while the dioxane solution of extracted HMF was separated via simple phase separation. Followed by water commixing, this HMF dioxane solution (with the HMF concentration of 6.3 wt %) was directly oxidized over Ru/C (393 K, 1 MPa O2) to produce FDCA without HMF isolation and alkali addition, affording FDCA yield near 90 %. This study integrates the fructose dehydration and HMF oxidation rationally via dioxane as the bridging solvent to achieve high FDCA yield without complex HMF purification steps, and thus proposes an applicable model for high-efficient production of FDCA in practice.