Efficient one-pot synthesis of 2,5-furandicarboxylic acid from fructose and 5-hydroxymethylfurfural using synergistically active Ce-Al composite catalyst under mild conditions

Abstract

Using tert-butyl hydroperoxide (TBHP) as a low-cost oxidant, we synthesized, characterized, and evaluated heterogeneous bifunctional oxide catalysts composed of the non-noble metals Ce and Al in specific molar ratios, supported on glucose-derived carbon, for the conversion of 5-hydroxymethylfurfural (5-HMF) to 2,5-furandicarboxylic acid (2,5-FDCA) in dimethyl sulfoxide (DMSO). TBHP offers two advantages: it functions as an oxidant and generates tert-butanol, a valuable industrial solvent. We fully investigated catalyst loading, temperature, 5-HMF:TBHP molar ratio, reaction time, and reuse impact on product yield while correlating with the catalyst’s textural and chemical properties. CAOC-1, the best catalyst, achieved 98 % conversion, 82.0 % yield, and 83.54 % selectivity of 2,5-FDCA in optimal conditions (5-HMF (1 mmol), TBHP (9 mmol), DMSO (5 gm), CAOC-1 (50 mg), Temp (120 °C), 24 h), with minimal yield reduction over five reuse cycles. We used the bifunctional CAOC-1 in a one-pot, two-step system to directly transform fructose to 2,5-FDCA under mild conditions (fructose (1 mmol), TBHP (9 mmol), DMSO (5 gm), CAOC-1 (50 mg), temp (120 °C), 26 h) with minimal process modifications. The yield and selectivity of 2,5-FDCA were 80.26 % and 83.94 %, respectively. We proposed mechanistic pathways for dehydration and oxidation reactions, highlighting the catalyst’s bifunctional nature in facilitating high 2,5-FDCA yields from fructose and 5-HMF. The formation of the distinct redox environment of Ce and Al on carbon, the various oxidation states, and the oxygen vacancies in the CAOC-1 catalyst—all of which most likely operate as base-free oxidation active sites. One-pot reaction processes involve bifunctional CAOC-1 catalysts, –OH, and redox active sites (Ce), which play a significant role in dehydration and oxidation reactions, respectively. 2,5-FDCA is crucial to produce polyethylene 2,5-furandicarboxylate (PEF), a sustainable bioplastic and alternative to PET.