Polyvinyl Alcohol Functionalized Solid Acid Catalyst DICAT-1 for Microwave-Assisted Synthesis of 5-Hydroxymethylfurfural in Green Solvent

Microwave-assisted cyclodehydration of fructose to 5-hydroxymethylfurfural (5-HMF) was studied herein over polyvinyl alcohol (PVA)-functionalized solid acid catalyst DICAT-1 in low-boiling green solvents. Of the tested solvent systems [isopropanol (IPA), tert-butyl alcohol, THF, acetone, CH3CN, DMF, and DMSO], IPA was the preferred low boiling point (LBP) reaction medium, resulting in 95% fructose conversion and 85% 5-HMF yield in 120s. The characteristic dispersibility and swelling properties of DICAT-1 in IPA had a significant effect on 5-HMF yield. The catalyst DICAT-1 was stable and robust under the reaction conditions and easily recycled. The structural and morphological characteristics of the catalyst were elucidated by FTIR spectroscopy, SEM/energy-dispersive X-ray spectroscopy, X-ray fluorescence spectroscopy, XRD, and N-2 sorption analysis. DICAT-1 has covalently bonded -SO3H active sites, an amorphous nature, and mesoporous surface morphology; these features result in excellent performance in IPA. Estimated values of turnover number, turnover frequency, E-factor, and process mass intensity categorize the overall process as environmentally safe for the production of 5-HMF. A catalytic mechanism for 5-HMF formation on DICAT-1 is proposed.