Two‐Step Synthesis of 2,5‐Furandicarboxylic Acid Through Biomass‐Derived 5‐(Hydroxymethyl)furfural in a Green Isopropanol–Water Solvent System

Abstract This study presents a one‐pot, two‐step process for synthesizing 2,5‐furandicarboxylic acid (FDCA) from whey permeate powder (WPP) using a green isopropanol–water solvent system. WPP, a cheese industry byproduct produced in large quantities, was chosen over glucose, fructose, or lactose due to its high biochemical oxygen demand and disposal challenges. In the first step, 5‐(hydroxymethyl)furfural (HMF) was produced from WPP, with process optimization via Box–Behnken design. Among various catalysts tested, a combination of AlCl 3 and FeCl 3 (6:1 weight ratio) was most effective, yielding 51.8% HMF under optimal conditions: 36.6 mg catalyst, 139.7 °C, and 1.48 h. Crude HMF was isolated via rotary evaporation with a 41.3% yield. In the second step, a non‐precious Cu─Fe─O catalyst was synthesized for oxidizing HMF to FDCA. Using pure HMF (1 wt%), the optimized conditions—2.8 equiv NaOH, 159.5 °C, and 5.7 h—achieved a 49.3% FDCA yield. Integration with WPP‐derived HMF (0.5 wt%) produced a 60.8% FDCA yield. Catalyst reuse studies showed consistent performance over four cycles without significant yield loss.